,transcriber's notes3 words in bold and italics have been transcribed as word and word1 respectively2 superscripts are indicated by 1 subscripts by 4 ,greek letters have been transliterated as alpha1 beta1 etc4 ,spelling and hyphenation have been standardised 7see list at end of text74 ,,turning ,,and ,,boring ,a ,,specialized ,,treatise ,,for ,,machinists1 ,,students ,,in ,,industrial ,,and ,,engineering ,,schools1 ,,and ,,apprentices1 ,,on ,,turning ,,and ,,boring ,,methods1 ,,including ,,modern ,,practice ,,with ,,engine ,,lathes1 ,,turret ,,lathes1 ,,vertical ,,and ,,horizontal ,,boring ,,machines ,,by ,,franklin ,d4 ,,jones ,,associate ,,editor ,,of ,,machinery ,,author ,,of ,,planing ,,and ,,milling ,,first ,,edition ,,fifth ,,printing ,,new ,,york ,,the ,,industrial ,,press ,,london3 ,,the ,,machinery ,,publishing ,,co41 ,,ltd4 #aiai ,,copyright1 #aiad ,,by ,,the ,,industrial ,,press ,,new ,,york ,,preface ,specialization in machine-tool manufacture has been developed to such a degree that there is need also for treatises which specialize on different classes of tools and their application in modern practice4 ,this book deals exclusively with the use of various types of turning and boring machines and their attachments1 and is believed to be unusually complete4 ,in addition to standard practice1 it describes many special operations seldom or never presented in text-books4 ,very little space is given to mere descriptions of different types of machine tools1 the principal purpose being to explain the use of the machine and the practical problems connected with its operation1 rather than the constructional details4 ,no attempt has been made to describe every machine or tool which might properly be included1 but rather to deal with the more important and useful operations1 especially those which illustrate general principles4 ,readers of mechanical literature are familiar with ,,machinery',s #be-;cent ,reference ,books1 of which one hundred and twenty-five different titles have been published during the past six years4 ,many subjects1 however1 cannot be adequately covered in all their phases in books of this size1 and in response to a demand for more comprehensive and detailed treatments on the more important mechanical subjects1 it has been deemed advisable to bring out a number of larger volumes1 of which this is one4 ,this work includes much of the material published in ,,machinery',s ,reference ,books ,nos4 #ia1 #ib and #ie1 together with a great amount of additional information on modern boring and turning methods4 ,it is a pleasure to acknowledge our indebtedness to the manufacturers who generously supplied illustrations and data1 including many interesting operations from actual practice4 ,much valuable information was also obtained from ,,machinery4 ,f4 ,d4 ,j4 ,,new ,,york1 ,may1 #aiad4 ,,contents ,,pages ,,chapter ,i ,,the ,,engine ,,lathe--,,turning ,,and ,,boring ,,operations ,general ,description of an ,engine ,lathe--,example of ,cylindrical ,turning--,facing the ,ends ,square with a ,side-tool--,turning ,tool--,turning ,work ,cylindrical--,roughing and ,finishing ,cuts--,filing and ,finishing--,aligning ,centers for ,cylindrical ,turning--,application of ,drivers or ,dogs--,lathe ,arbors or ,mandrels--,different ,types of ,lathe ,arbors--,mandrel or ,arbor ,press--,steadyrest for ,supporting ,flexible ,parts--,application of ,steadyrest when ,boring--,the ,follow-rest--,centering ,parts to be ,turned--,centering ,machine--,different ,forms of ,centers--,precaution ,when ,centering ,tool ,steel--,facing the ,ends of ,centered ,stock--,truing ,lathe ,centers--,universal1 ,independent and ,combination ,chucks--,application of ,chucks--,example of ,boring--,measuring ,bored ,holes--,setting ,work in the ,chuck--,inaccuracy from ,pressure of ,chuck ,jaws--,drilling and ,reaming--,holding ,work on ,faceplate--,application of ,angle-plate to ,faceplate--,supporting ,outer ,end of ,chucked ,work--,boring ,large ,castings in the ,lathe--,boring ,holes to a ,given ,center ,distance--,turning ,brass1 ,bronze and ,copper--,machining ,aluminum #a-ec ,,chapter ,,ii ,,lathe ,,turning ,,tools ,,and ,,cutting ,,speeds ,turning ,tools for ,general ,work--,tool-holders with ,inserted ,cutters--,the ,position of ,turning ,tools--,tool ,grinding--,shape or ,contour of ,cutting ,edge--,direction of ,top ,slope for ,turning ,tools--,clearance for the ,cutting ,edge--,angle of ,tool-point and ,amount of ,top ,slope--,grinding a ,lathe ,tool--,cutting ,speeds and ,feeds--,average ,cutting ,speeds for ,turning--,factors which ,limit the ,cutting ,speed--,rules for ,calculating ,cutting ,speeds--,feed of ,tool and ,depth of ,cut--,effect of ,lubricant on ,cutting ,speed--,lubricants ,used for ,turning--,lard ,oil as a ,cutting ,lubricant #ed-gi ,,chapter ,,iii ,,taper ,,turning--,,special ,,operations--,,fitting ,setting ,tailstock ,center for ,taper ,turning--,example of ,taper ,turning--,setting the ,tailstock ,center with a ,caliper ,tool--,setting the ,tailstock ,center with a ,square--,the ,taper ,attachment--,application of ,taper ,attachment--,height of ,tool when ,turning ,tapers--,taper ,turning with the ,compound ,rest--,accurate ,measurement of ,angles and ,tapers--,to ,find ,center ,distance for a ,given ,taper--,to ,find ,center ,distance for a ,given ,angle--,to ,find ,angle for ,given ,taper per ,foot--,to ,find ,angle for ,given ,disk ,dimensions--,use of the ,center ,indicator--,locating ,work by the ,button ,method--,eccentric ,turning--,turning a ,crankshaft in a ,lathe--,special ,crankshaft ,lathe--,operation of ,special ,crankshaft ,lathe--,spherical ,turning--,spherical ,turning ,attachments--,turning with ,front and ,rear ,tools--,a ,multiple-tool ,lathe--,examples of ,multiple ,turning--,knurling in the ,lathe--,relieving ,attachment--,application of ,relieving ,attachment--,relieving ,hobs or ,taps ,having ,spiral ,flutes--,classes of ,fits ,used in ,machine ,construction--,forced ,fits--,allowance for ,forced ,fits--,pressure for ,forced ,fits--,allowance for ,given ,pressure-,shrinkage ,fits #hj-acd ,,chapter ,,iv ,,thread ,,cutting ,,in ,,the ,,lathe ,selecting the ,change ,gears for ,thread ,cutting--,the ,thread ,tool--,cutting the ,thread--,indicator or ,chasing ,dial for ,catching ,threads--,principle of the ,thread ,indicator--,replacing ,sharpened ,thread ,tool--,use of ,compound ,rest for ,thread ,cutting--,threads ,commonly ,used--,multiple ,threads--,cutting a ,u4 ,s4 ,standard ,thread--,cutting a ,left-hand ,thread--,cutting a ,square ,thread--,cutting ,multiple ,threads--,setting ,tool ,when ,cutting ,multiple ,threads--,taper ,threading--,internal ,threading--,stop for ,thread ,tools--,the ,acme ,standard ,thread--,the ,whitworth ,thread--,worm ,threads--,coarse ,threading ,attachment--,testing the ,size of a ,thread--,the ,thread ,micrometer--,three-wire ,system of ,measuring ,threads--,rivett-,dock ,threading ,tool--,cutting ,screws to ,compensate for ,shrinkage--,calculating ,change ,gears for ,thread ,cutting--,lathes with ,compound ,gearing--,fractional ,threads--,change ,gears for ,metric ,pitches--,quick ,change-gear ,type of ,lathe #ace-agg ,,chapter ,v ,,turret ,,lathe ,,practice ,general ,description of a ,turret ,lathe--,example of ,turret ,lathe ,work--,machining ,flywheels in ,turret ,lathe--,finishing a ,flywheel at ,one ,setting in ,turret ,lathe--,finishing a ,webbed ,flywheel in ,two ,settings--,tools for ,turret ,lathes--,box-tools--,examples of ,box-tool ,turning--,hollow ,mills--,releasing ,die and ,tap ,holders--,self-opening ,die ,heads--,collapsing ,taps--,miscellaneous ,turret ,lathe ,tools--,turning ,gasoline ,engine ,pistons in ,turret ,lathe--,turning ,piston ,rings in ,turret ,lathe--,piston ,turning in ,pratt and ,whitney ,turret ,lathe--,attachment for ,turning ,piston ,rings--,turning ,worm-gear ,blanks in ,turret ,lathe--,turning ,bevel ,gear ,blanks--,shell ,turning ,operation in ,flat ,turret ,lathe--,chuck ,work in ,flat ,turret ,lathe--,double-spindle ,flat ,turret ,lathe--,automatic ,chucking and ,turning ,machine--,example of ,work on ,automatic ,turning ,machine--,determining ,speed and ,feed ,changes--,setting the ,turret ,slide--,setting the ,cross-slide ,cam--,setting the ,boring ,tool for ,recessing--,adjustments for ,automatic ,feed and ,speed ,changes--,turning ,flywheel in ,automatic ,chucking and ,turning ,machine--,automatic ,multiple-spindle ,chucking ,machine--,selecting ,type of ,turning ,machine #agh-bda ,,chapter ,,vi ,,vertical ,,boring ,,mill ,,practice ,boring and ,turning in a ,vertical ,boring ,mill--,holding and ,setting ,work on ,boring ,mill ,table--,turning in a ,boring ,mill--,boring ,operations--,turning ,tools for the ,vertical ,boring ,mill--,turning a ,flywheel on a ,vertical ,mill--,convex ,turning ,attachment for ,boring ,mills--,turning ,taper or ,conical ,surfaces--,turret-lathe ,type of ,vertical ,boring ,mill--,examples of ,vertical ,turret ,lathe ,work--,floating ,reamer ,holders--,multiple ,cylinder ,boring ,machine #bdb-bgd ,,chapter ,,vii ,,horizontal ,,boring ,,machines ,horizontal ,boring ,machine with ,vertical ,table ,adjustment--,drilling and ,boring--,cutters ,used--,cutter-heads for ,boring ,large ,holes--,cylinder ,boring--,boring a ,duplex ,gasoline ,engine ,cylinder--,examples of ,boring1 ,radial ,facing and ,milling--,fixture for ,cylinder ,lining or ,bushing--,horizontal ,boring ,machine of ,floor ,type #bge-big ,,index #bii-cjg ,,turning ,,and ,,boring ,,chapter ,i ,,the ,,engine ,,lathe--,,turning ,,and ,,boring ,,operations ,the standard engine lathe1 which is the type commonly used by machinists for doing general work1 is one of the most important tools in a machine shop1 because it is adapted to a great variety of operations1 such as turning all sorts of cylindrical and taper parts1 boring holes1 cutting threads1 etc4 ,the illustration ,fig4 #a shows a lathe which1 in many respects1 represents a typical design1 and while some of the parts are arranged differently on other makes1 the general construction is practically the same as on the machine illustrated4 ,the principal parts are the bed ,b1 the headstock ,h1 the tailstock ,t1 and the carriage ,c4 ,the headstock contains a spindle which is rotated by a belt that passes over the cone-pulley ,p1 and this spindle rotates the work1 which is usually held between pointed or conical centers h and h#a in the headstock and tailstock1 or in a chuck screwed onto the spindle instead of the faceplate ,f4 ,the carriage ,c can be moved lengthwise along the bed by turning handle d1 and it can also be moved by power1 the movement being transmitted from the headstock spindle either through gears a1 b1 c1 and lead-screw ,s1 or by a belt operating on pulleys p and p#a1 which drive the feed-rod ,r4 ,the lead-screw ,s is used when cutting threads1 and the feed-rod ,r for ordinary turning operations2 in this way the wear on the lead-screw is reduced and its accuracy is preserved4 ,illustration3 ,fig4 #a4 ,bradford ,belt-driven ,lathe--,view of ,front or ,operating ,side ,on the carriage1 there is a cross-slide ,d which can be moved at right angles to the lathe bed by handle e1 and on ,d there is an upper or compound slide ,e which can be swiveled to different positions4 ,the tool t1 that does the turning1 is clamped to the upper slide1 as shown1 and it can be moved with relation to the work by the movement of the carriage ,c along the bed1 or by moving slide ,d crosswise4 ,the lengthwise movement is used to feed the tool along the work when turning1 boring or cutting a screw1 and the crosswise movement for facing the ends of shafts1 etc41 or for radial turning4 ,when the tool is to be fed at an angle1 other than at right angles to the bed1 slide ,e1 which can be set to the required angle1 is used4 ,the lengthwise and crosswise feeding movements can be effected by power1 the lengthwise feed being engaged by tightening knob k1 and the cross-feed by tightening knob l4 ,the direction of either of these movements can also be reversed by shifting lever r4 ,ordinarily the carriage and slide are adjusted by hand to bring the tool into the proper position for turning to the required diameter1 and then the power feed 7operating in the desired direction7 is engaged4 ,the tailstock ,t can be clamped in different positions along the bed1 to suit the length of the work1 and its center h#a can be moved in or out for a short distance1 when adjusting it to the work1 by turning handle n4 ,illustration3 ,fig4 #b4 ,plan ,view of ,lathe ,headstock showing ,back-gears ,illustration3 ,fig4 #c4 ,feed ,mechanism of ,lathe ,apron ,as some metals are much harder than others1 and as the diameters of parts to be turned also vary considerably1 speed changes are necessary1 because if the speed is excessive1 the turning tool will become dull in too short a time4 ,these speed changes 7with a belt-driven lathe7 are obtained by placing the driving belt on different steps of cone-pulley ,p1 and also by the use of back-gears4 ,the cone-pulley can be connected directly with the spindle or be disengaged from it by means of bolt m4 ,when the pulley and spindle are connected1 five speeds 7with this particular lathe7 are obtained by simply shifting the driving belt to different steps of the cone4 ,when a slower speed is required than can be obtained with the belt on the largest step of the cone1 the latter is disconnected from the spindle1 and the back-gears ,g and ,g#a 7shown in the plan view ,fig4 #b7 are moved forward into mesh by turning handle ,o2 the drive is then from cone-pulley ,p and gear ,l to gear ,g1 and from gear ,g#a to the large gear ,j on the spindle4 ,when driving through the back-gears1 five more speed changes are obtained by shifting the position of the driving belt1 as before4 ,the fastest speed with the back-gears in mesh is somewhat slower than the slowest speed when driving direct or with the back-gears out of mesh2 hence1 with this particular lathe1 a series of ten gradually increasing speeds is obtained4 ,changes of feed for the turning tool are also required1 and these are obtained by shifting the belt operating on pulleys p and p#a to different-sized steps4 ,on some lathes these feed changes are obtained through gears which can be shifted to give different ratios4 ,many lathes also have gears in the headstock for changing the speeds4 ,illustration3 ,fig4 #d4 ,rear ,view of ,lathe ,apron ,front and rear views of the carriage apron1 which contains the feeding mechanism1 are shown in ,figs4 #c and #d1 to indicate how the feeds are engaged and reversed4 ,the feed-rod ,r 7,fig4 #a7 drives the small bevel gears ,a and ,a#a 7,figs4 #c and #d71 which are mounted on a slide ,s that can be moved by lever r to bring either bevel gear into mesh with gear ,b4 ,gear ,b is attached to pinion b 7see ,fig4 #c7 meshing with gear ,c1 which1 when knob k 7,fig4 #a7 is tightened1 is locked by a friction clutch to pinion c4 ,the latter pinion drives gear ,d which rotates shaft ,e4 ,a pinion cut on the end of shaft ,e engages rack ,k 7,fig4 #a7 attached to the bed1 so that the rotation of ,e 7which is controlled by knob k7 moves the carriage along the bed4 ,to reverse the direction of the movement1 it is only necessary to throw gear ,a into mesh and gear ,a#a out1 or vice versa1 by operating lever r4 ,when the carriage is traversed by hand1 shaft ,e and gear ,d are rotated by pinion d#a connected with handle d 7,fig4 #a74 ,the drive for the cross-feed is from gear ,c to gear ,f which can be engaged through a friction clutch 7operated by knob l1 ,fig4 #a7 with gear ,g meshing with a pinion ,h4 ,the latter rotates the cross-feed screw1 which passes through a nut attached to slide ,d 7,fig4 #a71 thus moving the latter at right angles to the ways of the bed4 ,the cross-feed is also reversed by means of lever r4 ,as previously explained1 lead-screw ,s is only used for feeding the carriage when cutting threads4 ,the carriage is engaged with this screw by means of two half-nuts ,n 7,fig4 #d7 that are free to slide vertically and are closed around the screw by operating lever u4 ,these half-nuts can only be closed when lever r is in a central or neutral position1 so that the screw feed and the regular turning feed cannot be engaged at the same time4 ,as previously mentioned1 lead-screw ,s1 ,fig4 #a1 is rotated from the lathe spindle1 through gears a1 b and c1 called change gears4 ,an assortment of these gears1 of various sizes1 is provided with the lathe1 for cutting screws of different pitch4 ,the gears to use for any pitch within the range of the lathe are given on the plate ,i4 ,example of ,cylindrical ,turning4--,having now considered the principal features of what might be called a standard lathe1 the method of using it in the production of machine parts will be explained4 ,to begin with a simple example of work1 suppose a steel shaft is to be turned to a diameter of #b-a_/d inches and a length of #ad-a_/b inches1 these being the finished dimensions4 ,we will assume that the rough stock is cut off to a length of #ad-e_/h inches and has a diameter of #b-e_/h inches4 ,the first step in this operation is to form conically shaped center-holes in each end of the piece as indicated at c in ,fig4 #e4 ,as all work of this kind is held1 while being turned1 between the centers h and h#a1 holes corresponding in shape to these centers are necessary to keep the work in place4 ,there are several methods of forming these center-holes1 as explained later4 ,after the work is centered1 a dog ,a is clamped to one end by tightening screw s2 it is then placed between the centers of the lathe4 ,the dog has a projecting end or tail1 as it is commonly called1 which enters a slot in the faceplate ,f and thereby drives or rotates the work1 when power is applied to the lathe spindle onto which the faceplate is screwed4 ,the tailstock center h#a1 after being oiled1 should be set up just tight enough to eliminate all play1 without interfering with a free rotary movement of the work4 ,this is done by turning handle n1 and when the center is properly adjusted1 the tailstock spindle containing the center is locked by tightening handle p4 7,ordinary machine oil is commonly used for lubricating lathe centers1 but a lubricant having more body should be used1 especially when turning heavy parts4 ,the following mixtures are recommended3 #a4 ,dry or powdered red lead mixed with a good grade of mineral oil to the consistency of cream4 #b4 ,white lead mixed with sperm oil with enough graphite added to give the mixture a dark lead color47 ,illustration3 ,fig4 #e4 ,plan ,view showing ,work ,mounted between ,centers of ,lathe ,facing the ,ends ,square with a ,side-tool4--,everything is now ready for the turning operation4 ,the ends of the piece should be faced square before turning the body to size1 and the tool for this squaring operation is shown in ,fig4 #f2 this is known as a side-tool4 ,it has a cutting edge e which shaves off the metal as indicated in the end view by the dotted lines4 ,the side f is ground to an angle so that when the tool is moved in the direction shown by the arrow1 the cutting edge will come in contact with the part to be turned2 in other words1 side f is ground so as to provide clearance for the cutting edge4 ,in addition1 the top surface against which the chip bears1 is beveled to give the tool keenness so that it will cut easily4 ,as the principles of tool grinding are treated separately in ,chapter ,,ii we shall for the present consider the tool's use rather than its form4 ,illustration3 ,fig4 #f4 ,lathe ,side-tool for ,facing ,ends of ,shafts1 etc4 ,for facing the end1 the side tool is clamped in the toolpost by tightening the screw u1 ,fig4 #e1 and it should be set with the cutting edge slightly inclined from a right-angled position1 the point being in advance so that it will first come into contact with the work4 ,the cutting edge should also be about the same height as the center of the work4 ,when the tool is set1 the lathe 7if belt-driven7 is started by shifting an overhead belt and the tool is then moved in until the point is in the position shown at ,a1 ,fig4 #g4 ,the tool-point is then fed against the end by handle d1 ,fig4 #e1 until a light chip is being turned off1 and then it is moved outward by handle e 7as indicated by the arrow at ,b1 ,fig4 #g71 the carriage remaining stationary4 ,as the movement of the tool-point is guided by the cross-slide ,d1 which is at right angles with the axis of the work1 the end will be faced square4 ,for short turning operations of this kind1 the power feeds ordinarily are not used as they are intended for comparatively long cuts4 ,if it were necessary to remove much metal from the end1 a number of cuts would be taken across it2 in this case1 however1 the rough stock is only #a_/h inch too long so that this end need only be made true4 ,illustration3 ,fig4 #g4 ,facing ,end with ,side-tool and ,turning ,work ,cylindrical ,after taking a cut as described1 the surface1 if left rough by the tool-point1 should be made smooth by a second or finishing cut4 ,if the tool is ground slightly round at the point and the cutting edge is set almost square1 as at ,c1 ,fig4 #g1 a smooth finish can be obtained2 the cut1 however1 should be light and the outward feed uniform4 ,the work is next reversed in the centers and the driving dog is placed on the end just finished2 the other end is then faced1 enough metal being removed to make the piece #ad-a_/b inches long1 as required in this particular case4 ,this completes the facing operation4 ,if the end of the work does not need to be perfectly square1 the facing operation can be performed by setting the tool in a right-angled position and then feeding it sidewise1 thus removing a chip equal to the width of one side4 ,evidently this method is confined to comparatively small diameters and the squareness of the turned end will be determined by the position of the tool's cutting edge4 ,turning ,tool--,turning ,work ,cylindrical4--,the tool used to turn the body to the required diameter is shaped differently from the side-tool1 the cutting edge ,e of most tools used for plain cylindrical turning being curved as shown in ,fig4 #h4 ,a tool of this shape can be used for a variety of cylindrical turning operations4 ,as most of the work is done by that part of the edge marked by arrow a1 the top of the tool is ground to slope back from this part to give it keenness4 ,the end ,f1 or the flank1 is also ground to an angle to provide clearance for the cutting edge4 ,if the tool did not have this clearance1 the flank would rub against the work and prevent the cutting edge from entering the metal4 ,this type of tool is placed about square with the work1 for turning1 and with the cutting end a little above the center4 ,illustration3 ,fig4 #h4 ,tool used for ,cylindrical ,turning ,before beginning to turn1 a pair of outside calipers or a micrometer should be set to #b-a_/d inches1 which1 in this case1 is the finished diameter of the work4 ,calipers are sometimes set by using a graduated scale as at ,a1 ,fig4 #i1 or they can be adjusted to fit a standard cylindrical gage of the required size as at ,b4 ,very often fixed caliper gages ,c are used instead of the adjustable spring calipers4 ,these fixed gages1 sometimes called snap gages1 are accurately made to different sizes1 and they are particularly useful when a number of pieces have to be turned to exactly the same size4 ,the turning tool is started at the right-hand end of the work and the tool should be adjusted with the left hand when beginning a cut1 as shown in ,fig4 #aj1 in order to have the right hand free for calipering4 ,a short space is first turned by hand feeding1 as at ,d1 ,fig4 #g1 and when the calipers show that the diameter is slightly greater than the finished size 7to allow for a light finishing cut1 either in the lathe or grinding machine7 the power feed for the carriage is engaged2 the tool then moves along the work1 reducing it as at ,e4 ,evidently1 if the movement is along a line b--b1 parallel with the axis a--a1 the diameter d will be the same at all points1 and a true cylindrical piece will be turned4 ,on the other hand1 if the axis a--a is inclined one way or the other1 the work will be made tapering2 in fact1 the tailstock center h#a can be adjusted laterally for turning tapers1 but for straight turning1 both centers must be in alignment with the carriage travel4 ,most lathes have lines on the stationary and movable parts of the tailstock base which show when the centers are set for straight turning4 ,these lines1 however1 may not be absolutely correct1 and it is good practice to test the alignment of the centers before beginning to turn4 ,this can be done by taking trial cuts1 at each end of the work 7without disturbing the tool's crosswise position71 and then comparing the diameters1 or by testing the carriage travel with a true cylindrical piece held between the centers as explained later4 ,illustration3 ,fig4 #i4 ,setting ,calipers by ,scale--,setting by ,gage--,fixed ,gage ,if the relative positions of the lathe centers are not known1 the work should be calipered as the cut progresses to see if the diameter d is the same at all points4 ,in case the diameter gradually increases1 the tailstock center should be shifted slightly to the rear before taking the next cut1 but if the diameter gradually diminishes1 the adjustment would1 of course1 be made in the opposite direction4 ,the diameter is tested by attempting to pass the calipers over the work4 ,when the measuring points just touch the work as they are gently passed across it1 the diameter being turned is evidently the same as the size to which the calipers are set4 ,illustration3 ,fig4 #aj4 ,views showing how the ,cross-slide and ,carriage are ,manipulated by ,hand when ,starting a ,cut--,view to ,left1 ,feeding ,tool ,laterally2 ,view to ,right1 ,feeding ,tool in a ,lengthwise ,direction ,as the driving dog is on one end1 the cut cannot be taken over the entire length1 and when the tool has arrived at say position x1 ,fig4 #e1 it is returned to the starting point and the work is reversed in the centers1 the dog being placed upon the other end4 ,the unfinished part is then turned1 and if the cross-slide is not moved1 the tool will meet the first cut4 ,it is not likely that the two cuts will be joined or blended together perfectly1 however1 and for this reason a cut should be continuous when this is possible4 ,roughing and ,finishing ,cuts4--,ordinarily in lathe work1 as well as in other machine work1 there are two classes of cuts1 known as roughing and finishing cuts4 ,roughing cuts are for reducing the work as quickly as possible almost to the required size1 whereas finishing cuts1 as the name implies1 are intended to leave the part smooth and of the proper size4 ,when the rough stock is only a little larger than the finished diameter1 a single cut is sufficient1 but if there is considerable metal to turn away1 one or more deep roughing cuts would have to be taken1 and1 finally1 a light cut for finishing4 ,in this particular case1 one roughing and one finishing cut would doubtless be taken1 as the diameter has to be reduced #c_/h inch4 ,ordinarily the roughing cut would be deep enough to leave the work about #a_/cb or perhaps #a_/af inch above the finished size4 ,when there is considerable metal to remove and a number of roughing cuts have to be taken1 the depth of each cut and the feed of the tool are governed largely by the pulling power of the lathe and the strength of the work to withstand the strain of a heavy cut4 ,the depth of roughing cuts often has to be reduced considerably because the part being turned is so flexible that a heavy cut would spring the work and cause the tool to gouge in4 ,of course1 just as few cuts as possible should be taken in order to save time4 ,the speed of the work should also be as fast as the conditions will allow for the same reason1 but as there are many things which govern the speed1 the feed of the tool1 and the depth of the cut1 these important points are referred to separately in ,chapter ,,ii4 ,filing and ,finishing4--,in many cases the last or finishing cut does not leave as smooth a surface as is required and it is necessary to resort to other means4 ,the method commonly employed for finishing in the lathe is by the use of a file and emery cloth4 ,the work is rotated considerably faster for filing than for turning1 and the entire surface is filed by a flat1 single-cut file1 held as shown in ,fig4 #aa4 ,the file is passed across the work and advanced sidewise for each forward stroke1 until the entire surface is finished4 ,the file should be kept in contact with the work continually1 but on the return stroke the pressure should be relieved4 ,the movement of the file during the forward or cutting stroke should be much slower than when filing in a vise4 ,by moving the file slowly1 the work can make a number of revolutions for each stroke1 which tends to keep it round1 as practically the same amount of metal is removed from the entire circumference4 ,on the other hand1 short rapid strokes tend to produce flat spots1 or at least an irregular surface1 especially if the work can only make part of a revolution for each cutting stroke4 ,the pressure on the file during the forward stroke should also be kept as nearly uniform as possible4 ,illustration3 ,fig4 #aa4 ,filing ,work after ,finishing ,cut is taken ,it is very difficult to file a part smooth and at the same time to keep it round and cylindrical1 and the more filing that has to be done1 the greater the chance of error4 ,for this reason1 the amount left for filing should be very small2 in fact1 the metal removed by filing should be just enough to take out the tool marks and give a smooth finish4 ,very often a satisfactory finish can be obtained with a turning tool1 and filing is not necessary at all4 ,the file generally used for lathe work is a single-cut bastard of mill section1 having a length of from #ab to #ad inches4 ,sometimes particles of metal collect between the teeth of a file and make deep scratches as the file is passed across the work4 ,when this occurs1 the teeth should be cleaned by using a wire brush or a file card1 which is drawn across the file in the direction of the teeth4 ,this forming of tiny particles between the teeth is known as pinning and it can sometimes be avoided by rubbing chalk on the file4 ,filing is not only done to obtain a smooth finish1 but also to reduce the work to an exact diameter1 as a very slight reduction can be made in this way4 ,illustration3 ,fig4 #ab4 ,two ,methods of ,aligning ,centers for ,cylindrical ,turning ,if a polish is desired1 this can be obtained by holding a piece of emery cloth tightly around the work as it revolves4 ,the coarseness of emery cloth is indicated by letters and numbers corresponding to the grain number of loose emery4 ,the letters and numbers for grits ranging from fine to coarse are as follows3 ,,ff1 ,f1 #abj1 #ajj1 #ij1 #hj1 #gj1 #fj1 #ed1 #df1 #dj4 ,for large work roughly filed1 use coarse cloth such as ,nos4 #df or #ed1 and then finer grades to obtain the required polish4 ,if the work has been carefully filed1 a good polish can be obtained with ,nos4 #fj and #ij cloth1 and a brilliant polish by finishing with ,no4 #abj and flour-emery4 ,most cylindrical parts can be finished more quickly and accurately in the grinder than in the lathe1 and many classes of work are1 at the present time1 simply rough-turned in the lathe and then ground to size in a cylindrical grinding machine4 ,aligning ,centers for ,cylindrical ,turning4--,when a rod or shaft must be turned cylindrical or to the same diameter throughout its entire length1 it is good practice to test the alignment of the centers1 before inserting the work4 ,the position of the tailstock center for cylindrical turning may be indicated by the coincidence of graduation marks on the base1 but if accuracy is necessary1 the relative position of the two centers should be determined in a more positive way4 ,a very simple and convenient method of testing the alignment is shown at ,a in ,fig4 #ab4 ,the work is first turned for a short distance1 near the dogged end1 as shown1 and the tool is left as set for this cut2 then the tailstock center is withdrawn and the work is moved sufficiently to permit running the tool back to the tailstock end without changing its original setting4 ,a short cut is then taken at this end and the diameters d and d#a are carefully compared4 ,in case there is any variation1 the tailstock center is adjusted laterally1 other trial cuts are taken1 and the test repeated4 ,another method is illustrated at ,b1 which requires the use of a test-bar t4 ,this bar should have accurately made centers and the ends finished to exactly the same diameter4 ,the lathe centers are aligned by placing the bar between them and then testing the position of the ends4 ,this can be done by comparing each end with a tool held in the toolpost and moved from one to the other by shifting the carriage1 but a better method is to clamp a test indicator i in the toolpost and bring it in contact with first one end of the bar and then the other4 ,if the dial does not register the same at each end1 it shows that the lathe centers are not in line4 ,even when centers are correctly set1 lathes that have been in use a long time do not always turn cylindrical or straight1 because if the ways that guide the carriage are worn unevenly1 the tool as it moves along does not remain in the same plane and this causes a variation in the diameter of the part being turned4 ,application of ,drivers or ,dogs4--,work that is turned between centers is sometimes driven by a dog which is so short for the faceplate that the bent driving end bears against the bottom a of the faceplate slot1 as shown at ,a1 ,fig4 #ac4 ,if the dog is nearly the right length1 it may allow the headstock center to enter the center in the work part way1 with the result that the turned surface is not true with the centers4 ,when a driving dog of this type is used1 care should be taken to see that it moves freely in the faceplate slot and does not bind against the bottom4 ,by using a straight dog 7,b71 which is driven by a pin b bolted to the faceplate1 all danger from this source is eliminated4 ,the straight dog1 however1 is used more particularly to do away with the leverage l of a bent dog1 as this leverage tends to spring a flexible part when a cut is being taken4 ,illustration3 ,fig4 #ac4 7,a7 ,dog that is too ,short for ,faceplate4 7,b7 ,straight ,driving ,dog ,straight dogs are also made with two driving ends which engage pins on opposite sides of the faceplate4 ,this type is preferable because it applies the power required for turning1 evenly to the work1 which still further reduces the tendency to spring it out of shape4 ,the principal objection to the double-ended type lies in the difficulty of adjusting the driving pins so that each bears with equal pressure against the dog4 ,the double-ended driver is often used for large work especially if deep roughing cuts are necessary4 ,lathe ,arbors or ,mandrels4--,when it is necessary to turn the outside of a part having a hole through it1 centers cannot1 of course1 be drilled in the ends and other means must be resorted to4 ,we shall assume that the bushing ,b1 ,fig4 #ad1 has a finished hole through the center1 and it is desired to turn the outside cylindrical and concentric with the hole4 ,this could be done by forcing a tightly-fitted arbor ,m1 having accurately-centered ends1 into the bushing and inserting the mandrel and work between the lathe centers h and h#a as shown4 ,evidently1 if the arbor runs true on its centers1 the hole in the bushing will also run true and the outside can be turned the same as though the arbor and bushing were a solid piece4 ,from this it will be seen that an arbor simply forms a temporary support for parts that are bored and therefore cannot be centered4 ,illustration3 ,fig4 #ad4 ,bushing mounted on ,arbor for ,turning ,another example of work that would be turned on an arbor is shown in ,fig4 #ae4 ,this is a small cast-iron wheel having a finished hole through the hub1 and the outer surface and sides of the rim are to be turned true with this hole4 ,in this case1 the casting would also be held by pressing a mandrel through the hub2 as shown4 ,this method1 however1 would only apply to comparatively small wheels because it would be difficult1 if not impossible1 to prevent a large wheel from turning on the arbor when taking a cut1 and even if it could be driven1 large work could be done to better advantage on another type of machine4 7,the vertical boring mill is used extensively for turning large wheels1 as explained in ,chapter ,,vi47 ,when turning the outside of the rim1 a tool similar to that shown at t should be used1 but for facing or turning the sides1 it might be better1 if not necessary1 to use tools having bent ends as shown by the dotted lines2 in fact1 turning tools of various kinds are made with the ends bent to the right or left1 as this enables them to be used on surfaces that could not be reached very well with a straight tool4 ,if a comparatively large pulley is mounted near the end of the arbor1 it can be driven directly by pins attached to the faceplate and engaging the pulley arms4 ,this method of driving is often employed when the diameter to be turned is large and the hole for the arbor is so small that there will not be sufficient friction for driving4 ,illustration3 ,fig4 #ae4 ,turning ,pulley ,held on an ,arbor ,different ,types of ,lathe ,arbors4--,three different types of lathe arbors are shown in ,fig4 #af4 ,the kind shown at ,a is usually made of tool steel and the body is finished to a standard size4 ,the ends are somewhat reduced and flat spots are milled1 as shown1 to give the clamping screw of the dog a good grip4 ,the body of the arbor is usually tapered about #j4jjf inch per foot4 ,this taper makes it easier to insert the arbor in a close-fitting hole1 and it also permits slight variations in the diameter of different holes4 ,as to hardening1 the practice at the present time among manufacturers is to harden arbors all over1 but for extremely accurate work1 an arbor having hardened ends and a soft body is generally considered superior1 as there is less tendency of distortion from internal stresses4 ,hardened arbors are seasoned before finish-grinding to relieve these internal stresses4 ,the solid type ,a1 ,fig4 #af1 is used very extensively1 but in shops where a great variety of work is being done and there are many odd-sized holes1 some form of expanding arbor ,b can be used to advantage4 ,this type1 instead of being solid1 consists of a tapering inner arbor ,m on which is placed a split bushing that can be expanded1 within certain limits1 by driving in the tapering member4 ,the advantage of this type is that a comparatively small stock of arbors is required1 as different-sized bushings can be used4 ,this type can also be fitted to holes of odd sizes1 whereas a solid arbor must be provided for each different size hole1 unless the variation is very slight4 ,the latter are1 however1 more accurate than the expanding type4 ,illustration3 ,fig4 #af4 ,different ,types of ,lathe ,arbors ,another form of expanding arbor is shown at ,c4 ,this type has a straight body ,n in which four tapering grooves are cut lengthwise1 as shown1 and there is a sleeve ,s1 containing four slots that are located to correspond with the tapering grooves4 ,strips s are fitted into these slots1 and as the part ,n is driven in1 the strips are moved outward as they ascend the tapering grooves4 ,by having different sets of these strips of various heights1 one arbor of this type can be made to cover quite a range of sizes4 ,it is not suited1 however1 to thin work1 as the pressure1 being concentrated in four places1 would spring a flexible part out of shape4 ,the cone arbor or mandrel shown at ,a1 in ,fig4 #ag1 is convenient for holding parts having comparatively large holes1 as it can be adjusted for quite a range of diameters4 ,the work is gripped between the two cones c and c#a which are forced together by nut n4 ,the cones are prevented from turning upon the arbor by keys4 ,this style of arbor should not be used for accurate work4 ,the threaded arbor ,b is used for facing the sides of nuts square with the tapped hole4 ,when a nut is first put upon the arbor1 the rough side comes against an equalizing washer w4 ,this washer rests against a spherical seat so that it can shift to provide a uniform bearing for the rough side of the nut1 even though it is not square with the tapped hole4 ,this feature prevents the nut from being canted on the arbor and insures an accurately faced nut4 ,the revolving conical center shown at ,c is often used for holding a pipe or tube while turning the outside4 ,the cone is adjusted to fit into the hole of the pipe1 by means of the tailstock spindle1 and the opposite end is usually held in a chuck4 ,illustration3 ,fig4 #ag4 7,a7 ,cone ,arbor4 7,b7 ,nut ,arbor4 7,c7 ,pipe ,center ,particular care should be taken to preserve the accuracy of the centers of lathe arbors by keeping them clean and well-oiled while in use4 ,mandrel or ,arbor ,press4--,the best method of inserting an arbor of the solid type in a hole is by using a press1 ,fig4 #ah1 designed for that purpose1 but if such a press is not available and it is necessary to drive the mandrel in1 a soft hammer1 made of copper1 lead or other soft material1 should be used to protect the centered end of the arbor4 ,in either case1 the arbor should not be forced in too tightly1 for if it fits properly1 this will not be necessary in order to hold the work securely4 ,on the other hand1 the work might easily be broken by attempting to force the arbor in as far and as tightly as possible4 ,in using the arbor press1 the work is placed on the base ,b with the hole in a vertical position1 and the arbor 7which should be oiled slightly7 is forced down into it by ram ,r1 operated by lever ,l4 ,slots are provided in the base1 as shown1 so that the end of the arbor can come through at the bottom of the hole4 ,the lever of this particular press is counter-weighted so that it rises to a vertical position when released4 ,the ram can then be adjusted quickly to any required height by the handwheel seen at the left4 ,illustration3 ,fig4 #ah4 ,press for ,forcing ,arbors into ,work ,some shops are equipped with power-driven mandrel or arbor presses4 ,this type is particularly desirable for large work1 owing to the greater pressure required for inserting mandrels that are comparatively large in diameter4 ,one well-known type of power press is driven by a belt1 and the downward pressure of the ram is controlled by a handwheel4 ,the ram is raised or lowered by turning this handwheel in one direction or the other1 and a gage shows how much pressure is being applied4 ,this type of press can also be used for other purposes1 such as forcing bushings or pins into or out of holes1 bending or straightening parts1 or for similar work4 ,illustration3 ,fig4 #ai4 ,steadyrest and ,follow-rest for ,supporting ,flexible ,parts ,steadyrest for ,supporting ,flexible ,parts4--,occasionally long slender shafts1 rods1 etc41 which have to be turned1 are so flexible that it is necessary to support them at some point between the lathe centers4 ,an attachment for the lathe known as a steadyrest is often used for this purpose4 ,a steadyrest is composed of a frame containing three jaws ,j 7,fig4 #ai71 that can be adjusted in or out radially by turning screws ,s4 ,the frame is hinged at h1 thus allowing the upper half to be swung back 7as shown by the dotted lines7 for inserting or removing the work4 ,the bolt-clamp c holds the hinged part in the closed position4 ,the base of the frame has ,v-grooves in it that fit the ways of the lathe bed4 ,when the steadyrest is in use1 it is secured to the bed by clamp ,c1 and the jaws ,j are set in against the work1 thus supporting or steadying it during the turning operation4 ,the steadyrest must1 of course1 be located at a point where it will not interfere with the turning tool4 ,illustration3 ,fig4 #bj4 ,application of ,steadyrest to a ,flexible ,rod ,fig4 #bj shows the application of the steadyrest to a long forged rod1 having one small end1 which makes it too flexible to be turned without support4 ,as this forging is rough1 a true surface n a little wider than the jaws ,j 7,fig4 #ai7 is first turned as a bearing for the jaws4 ,this should be done very carefully to prevent the work from mounting the tool4 ,a sharp pointed tool should be used and very light cuts taken4 ,the steadyrest is next clamped to the lathe bed opposite the turned surface1 and the jaws are adjusted in against this surface1 thus forming a bearing4 ,care should be taken not to set up the jaws too tightly1 as the work should turn freely but without play4 ,the large part of the rod and central collar are then turned to size1 this half being machined while the small part is in the rough and as stiff as possible4 ,the rod is then reversed and the steadyrest is applied to the part just finished1 as shown at ,b1 thus supporting the work while the small end is being turned4 ,that part against which the jaws bear should be kept well oiled1 and if the surface is finished it should be protected by placing a strip of emery cloth beneath the jaws with the emery side out2 a strip of belt leather is also used for this purpose1 the object in each case being to prevent the jaws from scratching and marring the finished surface1 as they tend to do1 especially if at all rough4 ,if the work were too flexible to permit turning a spot at n1 this could be done by first spotting it at some point o1 and placing the steadyrest at that point while turning another spot at n4 ,sometimes it is desirable to apply a steadyrest to a surface that does not run true and one which is not to be turned2 in such a case a device called a cat-head is used4 ,this is simply a sleeve ,s 7,fig4 #ba7 which is placed over the untrue surface to serve as a bearing for the steadyrest4 ,the sleeve is made to run true by adjusting the four set-screws at each end1 and the jaws of the steadyrest are set against it1 thus supporting the work4 ,illustration3 ,fig4 #ba4 ,cat-head which is sometimes used as ,bearing for ,steadyrest ,application of ,steadyrest when ,boring4--,another example illustrating the use of the steadyrest is shown in ,fig4 #bb4 ,the rod ,r is turned on the outside and a hole is to be bored in the end 7as shown by dotted lines7 true with the outer surface4 ,if the centers used for turning the rod are still in the ends1 as they would be ordinarily1 this work could be done very accurately by the following method3 ,the rod is first placed between the centers as for turning1 with a driving dog ,d attached1 and the steadyrest jaws ,j are set against it near the outer end1 as shown4 ,before any machine work is done1 means must be provided for holding the rod back against the headstock center h1 because1 for an operation of this kind1 the outer end cannot be supported by the tailstock center2 consequently the work tends to shift to the right4 ,one method of accomplishing this is shown in the illustration4 ,a hardwood piece w1 having a hole somewhat larger than the work1 is clamped against the dog1 in a crosswise position1 by the swinging bolts and thumb-screws shown4 ,if the dog is not square with the work1 the wood piece should be canted so that the bearing will not be all on one side4 ,for large heavy parts a similar bridle or hold-back--as this is commonly called--is made by using steel instead of wood for the part w4 ,another very common method which requires no special equipment is illustrated in ,fig4 #bc4 ,an ordinary leather belt lacing ,l is attached to the work and faceplate while the latter is screwed off a few turns as shown4 ,then the lacing is drawn up by hand and tied1 and the faceplate is screwed onto the spindle1 thus tightening the lacing and drawing the work against the headstock center4 ,the method of applying the lacing is quite clearly indicated in the illustration4 ,if a small driving faceplate is used1 it may be necessary to drill holes for the belt lacing1 as shown4 ,illustration3 ,fig4 #bb4 ,shaft supported by ,steadyrest for ,drilling and ,boring ,end ,a hole is next drilled in the end of the rod by using a twist drill in the tailstock4 ,if the hole is finished by boring1 a depth mark should be made on the tool shank that will warn the workman of the cutting end's approach to the bottom4 ,a chuck can also be used in connection with a steadyrest for doing work of this kind1 as shown in ,fig4 #bd1 the end of the rod being held and driven by the chuck ,c4 ,if the piece is centered1 it can be held on these centers while setting the steadyrest and adjusting the chuck1 but if the ends are without centers1 a very good way is to make light centers in the ends with a punch2 after these are properly located they are used for holding the work until the steadyrest and chuck jaws have been adjusted4 ,in case it is necessary to have the end hole very accurate with the outside of the finished rod1 a test indicator ,i should be applied to the shaft as shown4 ,this is an instrument which shows with great accuracy whether a rotating part runs true and it is also used for many other purposes in machine shops4 ,the indicator is held in the lathe toolpost and the contact point beneath the dial is brought against the work4 ,if the latter does not run true1 the hand of the indicator vibrates and the graduations on the dial show how much the work is out in thousandths of an inch4 ,illustration3 ,fig4 #bc4 ,hold-back used when ,outer ,end of ,work is held in ,steadyrest ,the ,follow-rest4--,when turning long slender parts1 such as shafts1 etc41 a follow-rest is often used for supporting the work4 ,the follow-rest differs from the steadyrest in that it is attached to and travels with the lathe carriage4 ,the type illustrated to the right in ,fig4 #ai has two adjustable jaws which are located nearly opposite the turning tool1 thus providing support where it is most needed4 ,in using this rest1 a cut is started at the end and the jaws are adjusted to this turned part4 ,the tool is then fed across the shaft1 which cannot spring away from the cut because of the supporting jaws4 ,some follow-rests have1 instead of jaws1 a bushing bored to fit the diameter being turned1 different bushings being used for different diameters4 ,the bushing forms a bearing for the work and holds it rigidly4 ,whether a bushing or jaws are used1 the turning tool is slightly in advance of the supporting member4 ,illustration3 ,fig4 #bd4 ,testing ,work with ,dial ,indicator ,centering ,parts to be ,turned4--,as previously mentioned1 there are a number of different methods of forming center-holes in the ends of parts that have to be turned while held between lathe centers4 ,a method of centering light work1 and one that requires few special tools1 is first to locate a central point on the end and then drill and ream the center-hole by using the lathe itself4 ,hermaphrodite dividers are useful for finding the center1 as illustrated at ,a1 ,fig4 #be1 but if the work is fairly round1 a center-square ,b is preferable4 ,a line is scribed across the end and then another line at right angles to the first by changing the position of the square2 the intersection of these two lines will be the center1 which should be marked by striking a pointed punch ,c with a hammer4 ,if a cup or bell center-punch ,d is available1 it will not be necessary to first make center lines1 as the conical part shown locates the punch in a central position4 ,this style of punch should only be used on work which is fairly round4 ,illustration3 ,fig4 #be4 ,centering ,end with ,punch preparatory to ,drilling ,after small centers have been located in both ends1 their position can be tested by placing the work between the lathe centers and rotating it rapidly by drawing the hand quickly across it4 ,by holding a piece of chalk close to the work as it spins around1 a mark will be made on the high side if the centers are not accurate2 the centers are then shifted toward these marks4 ,if the work is close to the finished diameter1 the centers should1 of course1 be located quite accurately in order that the entire surface of the work will be turned true when it is reduced to the finished size4 ,one method of forming these center-holes is indicated in ,fig4 #bf4 ,a chuck ,c is screwed onto the spindle in place of the faceplate1 and a combination center drill and reamer ,r is gripped by the chuck jaws and set to run true4 ,the center is then drilled and reamed at one end by pressing the work against the revolving drill with the tailstock spindle1 which is fed out by turning handle n4 ,the piece is then reversed for drilling the opposite end4 ,the work may be kept from revolving while the centers are being drilled and reamed1 by attaching a dog to it close to the tailstock end and then adjusting the cross-slide until the dog rests upon the slide4 ,many parts can be held by simply gripping them with one hand4 ,from the foregoing it will be seen that the small centers made by punch ,c1 ,fig4 #be1 serve as a starting point for the drill and also as a support for the outer end of the work while the first hole is being drilled4 ,illustration3 ,fig4 #bf4 ,drilling ,centers in the ,lathe ,the form of center-hole produced by a combination drill and reamer is shown by the lower left-hand view in ,fig4 #bg4 ,a small straight hole a in the bottom prevents the point of the lathe center from coming in contact with the work and insures a good bearing on the conical surface c4 ,the standard angle for lathe centers is sixty degrees1 as the illustration shows1 and the tapering part of all center-holes should be made to this angle4 ,illustration3 ,fig4 #bg4 ,centers of ,incorrect and ,correct ,form ,illustration3 ,fig4 #bh4 ,special ,machine for ,centering ,parts to be ,turned ,centering ,machine4--,many shops have a special machine for forming centers which enables the operation to be performed quickly4 ,one type of centering machine is shown in ,fig4 #bh4 ,the work is gripped in a chuck ,c that automatically locates it in a central position so that it is not necessary to lay out the end before drilling4 ,there are two spindles s1 one of which holds the drill and the other the countersink1 and these are rotated by a belt passing over pulley ,p4 ,each of these spindles is advanced by lever ,l and either of them can be moved to a position central with the work1 as they are mounted in a swiveling frame4 ,in operating this machine1 a small straight hole is first made by a twist drill held in one of the spindles2 the other spindle is then moved over to the center and the hole is reamed tapering4 ,the arrangement is such that neither spindle can be advanced by the feeding lever except when in a central position4 ,the amount that each spindle can be advanced is limited by a fixed collar inside the head1 and there is also a swinging adjustable stop against which the end of the work should be placed before tightening the chuck4 ,these two features make it possible to ream center holes of the same size or depth in any number of pieces4 ,illustration3 ,fig4 #bi4 ,the ,imperfect ,center ,bearing is the ,result of ,centering before ,straightening ,different ,forms of ,centers4--,in some poorly equipped shops it is necessary to form centers by the use of a center-punch only1 as there is no better tool4 ,if the end of the punch has a sixty-degree taper1 a fair center can be formed in this way1 but it is not a method to be recommended1 especially when accurate work is required4 ,sometimes centers are made with punches that are too blunt1 producing a shallow center1 such as the one shown in the upper left-hand view1 ,fig4 #bg4 ,in this case all the bearing is on the point of the lathe center1 which is the worst possible place for it4 ,another way is to simply drill a straight hole as in the upper view to the right2 this is also bad practice in more than one respect4 ,the lower view to the right shows a form of center which is often found in the ends of lathe arbors1 the mouth of the center being rounded1 at r1 and the arbor end recessed as shown4 ,the rounded corner prevents the point of the lathe center from catching when it is moved rapidly towards work which is not being held quite centrally 7as shown by the illustration71 and the end is recessed to protect the center against bruises4 ,stock that is bent should always be straightened before the centers are drilled and reamed4 ,if the work is first centered and then straightened the bearing on the lathe center would be as shown in ,fig4 #bi4 ,the center will then wear unevenly with the result that the surfaces last turned will not be concentric with those which were finished first4 ,illustration3 ,fig4 #cj4 ,tool ,steel should be centered ,concentric1 in order to remove the ,decarbonized ,outer ,surface ,precaution ,when ,centering ,tool ,steel4--,ordinarily centers are so located that the stock runs approximately true before being turned1 but when centering tool steel to be used in making tools1 such as reamers1 mills1 etc41 which need to be hardened1 particular care should be taken to have the rough surface run fairly true4 ,this is not merely to insure that the piece will true-up1 as there is a more important consideration1 the disregard of which often affects the quality of the finished tool4 ,as is well known1 the degree of hardness of a piece of tool steel that has been heated and then suddenly cooled depends upon the amount of carbon that it contains1 steel that is high in carbon becoming much harder than that which contains less carbon4 ,furthermore1 the amount of carbon found at the surface1 and to some little depth below the surface of a bar of steel1 is less than the carbon content in the rest of the bar4 ,this is illustrated diagrammatically in ,fig4 #cj by the shaded area in the view to the left4 7,this decarbonization is probably due to the action of the oxygen of the air on the bar during the process of manufacture47 ,if stock for a reamer is so centered that the tool removes the decarbonized surface only on one side1 as illustrated to the right1 evidently when the reamer is finished and hardened the teeth on the side ,a will be harder than those on the opposite side1 which would not have been the case if the rough bar had been centered true4 ,to avoid any trouble of this kind1 stock that is to be used for hardened tools should be enough larger than the finished diameter and so centered that this decarbonized surface will be entirely removed in turning4 ,illustration3 ,fig4 #ca4 ,three ,methods of ,facing the ,ends ,square ,facing the ,ends of ,centered ,stock4--,as a piece of work is not properly centered until the ends are faced square1 we will consider this operation in connection with centering4 ,some machinists prefer lathe centers that are cut away as shown at ,a1 ,fig4 #ca1 so that the point of the side tool can be fed in far enough to face the end right up to the center hole4 ,others1 instead of using a special center1 simply loosen the regular one slightly and then1 with the tool in a position as at ,b1 face the projecting teat by feeding both tool and center inward as shown by the arrow4 ,whenever this method is employed1 care should be taken to remove any chips from the center hole which may have entered4 ,a method which makes it unnecessary to loosen the regular center1 or to use a special one1 is to provide clearance for the tool-point by grinding it to an angle of approximately forty-five degrees1 as shown at ,c4 ,if the tool is not set too high1 it can then be fed right up to the lathe center and the end squared without difficulty4 ,as for the special center ,a1 the use of special tools and appliances should always be avoided unless they effect a saving in time or their use makes it possible to accomplish the same end with less work4 ,truing ,lathe ,centers4--,the lathe centers should receive careful attention especially when accurate work must be turned4 ,if the headstock center does not run true as it revolves with the work1 a round surface may be turned1 but if the position of the driving dog with reference to the faceplate is changed1 the turned surface will not run true because the turned surface is not true with the work centers4 ,furthermore1 if it is necessary to reverse the work for finishing the dogged or driving end1 the last part turned will be eccentric to the first4 ,therefore1 the lathe centers should be kept true in order to produce turned surfaces that are true or concentric with the centered ends1 as it is often necessary to change the part being turned end for end for finishing1 and any eccentricity between the different surfaces would1 in many cases1 spoil the work4 ,illustration3 ,fig4 #cb4 ,grinder for ,truing ,lathe ,centers ,some lathes are equipped with hardened centers in both the head-and tailstock and others have only one hardened center which is in the tailstock4 ,the object in having a soft or unhardened headstock center is to permit its being trued by turning1 but as a soft center is quite easily bruised and requires truing oftener than one that is hard1 it is better to have both centers hardened4 ,special grinders are used for truing these hardened centers4 ,one type that is very simple and easily applied to a lathe is shown in ,fig4 #cb4 ,this grinder is held in the lathe toolpost and is driven by a wheel ,a that is held in contact with the cone-pulley4 ,the emery wheel ,b is moved to a position for grinding by adjusting the carriage and cross-slide1 and it is traversed across the conical surface of the center by handle ,c4 ,as the grinding proceeds1 the wheel is fed inward slightly by manipulating the cross-slide4 ,this grinder is set to the proper angle by placing the two centered ends ,d and ,d#a between the lathe centers1 which should be aligned as for straight turning4 ,the grinding spindle will then be #cj degrees from the axis of the lathe spindle4 ,the grinder should be carefully clamped in the toolpost so that it will remain as located by the centered ends4 ,after the tailstock center is withdrawn1 the emery wheel is adjusted for grinding4 ,as the wheel spindle is #cj degrees from the axis of the lathe spindle1 the lathe center is not only ground true but to an included angle of #fj degrees1 which is the standard angle for lathe centers4 ,there are many other styles of center grinders on the market1 some of which are driven by a small belt from the cone-pulley and others by electric motors which are connected with ordinary lighting circuits4 ,the tailstock center is ground by inserting it in the spindle in place of the headstock center4 ,before a center is replaced in its spindle1 the hole should be perfectly clean as even a small particle of dirt may affect the alignment4 ,the center in the headstock is usually referred to as the live center because it turns around when the lathe is in use1 and the center in the tailstock as the dead center1 because it remains stationary4 ,universal1 ,independent and ,combination ,chucks4--,many parts that are turned in the lathe are so shaped that they cannot be held between the lathe centers like shafts and other similar pieces and it is often necessary to hold them in a chuck ,a1 ,fig4 #cc1 which is screwed onto the lathe spindle instead of the faceplate4 ,the work is gripped by the jaws ,j which can be moved in or out to accommodate various diameters4 ,there are three classes of chucks ordinarily used on the lathe1 known as the independent1 universal and combination types4 ,the independent chuck is so named because each jaw can be adjusted in or out independently of the others by turning the jaw screws ,s with a wrench4 ,the jaws of the universal chuck all move together and keep the same distance from the center1 and they can be adjusted by turning any one of the screws ,s1 whereas with the independent type the chuck wrench must be applied to each jaw screw4 ,the combination chuck1 as the name implies1 may be changed to operate either as an independent or universal type4 ,the advantage of the universal chuck is that round and other parts of a uniform shape are located in a central position for turning without any adjustment4 ,the independent type is1 however1 preferable in some respects as it is usually stronger and adapted for holding odd-shaped pieces because each jaw can be set to any required position4 ,illustration3 ,fig4 #cc4 7,a7 ,lathe ,chuck4 7,b7 ,faceplate ,jaw ,application of ,chucks4--,as an example of chuck work1 we shall assume that the sides of disk ,d1 ,fig4 #cd1 are to be turned flat and parallel with each other and that an independent chuck is to be used4 ,first the chuck is screwed onto the lathe spindle after removing the faceplate4 ,the chuck jaws are then moved out or in1 as the case may be1 far enough to receive the disk and each jaw is set about the same distance from the center by the aid of concentric circles on the face of the chuck4 ,the jaws are then tightened while the disk is held back against them to bring the rough inner surface in a vertical plane4 ,if the work is quite heavy1 it can be held against the chuck1 before the jaws are tightened1 by inserting a piece of wood between it and the tailstock center2 the latter is then run out far enough to force the work back4 ,the outside or periphery of the disk should run nearly true and it may be necessary to move the jaws in on one side and out on the other to bring the disk to a central position4 ,to test its location1 the lathe is run at a moderate speed and a piece of chalk is held near the outer surface4 ,if the latter runs out1 the high side will be marked by the chalk1 and this mark can be used as a guide in adjusting the jaws4 ,it should be remembered that the jaws are moved only one-half the amount that the work runs out4 ,illustration3 ,fig4 #cd4 7,a7 ,radial ,facing4 7,b7 ,boring ,pulley ,held in ,chuck ,a round-nosed tool t of the shape shown can be used for radial facing or turning operations of the kind illustrated4 ,this tool is similar to the form used when turning between centers1 the principal difference being in the direction of the top slope4 ,the radial facing tool should be ground to slope downward toward a 7see ,fig4 #ce7 whereas the regular turning tool slopes toward b1 the inclination in each case being away from that part of the cutting edge which does the work4 ,the cutting edge should be the same height as the lathe centers1 and the cut is taken by feeding the tool from the outside in to the center4 ,the cut is started by hand and then the power feed is engaged1 except for small surfaces4 ,the first cut should1 if possible1 be deep enough to get beneath the scale1 especially if turning cast iron1 as a tool which just grazes the hard outer surface will be dulled in a comparatively short time4 ,if it were simply necessary to turn a true flat surface and the thickness of the disk were immaterial1 two cuts would be sufficient1 unless the surface were very uneven1 the first or roughing cut being followed by a light finishing cut4 ,for a finishing cut1 the same tool could be used1 but if there were a number of disks to be faced1 a square-nosed tool ,f1 ,fig4 #ce1 could probably be used to better advantage4 ,this type has a broad flat cutting edge that is set parallel with the rough-turned surface and this broad edge enables a coarse feed to be taken1 thus reducing the time required for the finishing cut4 ,if a coarse feed were taken with the round tool1 the turned surface would have spiral grooves in it1 whereas with the broad cutting edge1 a smooth surface is obtained even though the feed is coarse4 ,the amount of feed per revolution of the work1 however1 should always be less than the width w of the cutting edge4 ,very often broad tools cannot be used for finishing cuts1 especially when turning steel1 because their greater contact causes chattering and results in a rough surface4 ,an old and worn lathe is more liable to chatter than one that is heavy and well-built1 and as the diameter of the work also makes a difference1 a broad tool cannot always be used for finishing1 even though1 theoretically1 it would be preferable4 ,after one side of the disk is finished1 it is reversed in the chuck1 the finished surface being placed against the jaws4 ,the remaining rough side is then turned1 care being taken when starting the first cut to caliper the width of the disk at several points to make sure that the two sides are parallel4 ,illustration3 ,fig4 #ce4 ,tools ,ground so that ,top ,slopes away from ,working ,part of ,cutting ,edge ,example of ,boring4--,another example of chuck work is shown at ,b1 ,fig4 #cd4 ,in this case a cast-iron pulley is to have a true hole h bored through the hub4 7,the finishing of internal cylindrical surfaces in a lathe is referred to as boring rather than turning47 ,the casting should be set true by the rim instead of by the rough-cored hole in the hub2 this can be done by the use of chalk as previously explained4 ,even though a universal type of chuck were used1 the jaws of which1 as will be recalled1 are self-centering1 it might be necessary to turn the pulley relative to the chuck as a casting sometimes runs out because of rough spots or lumps which happen to come beneath one or more of the jaws4 ,illustration3 ,fig4 #cf4 ,boring ,tool ,the shape of tool t for boring is quite different from one used for outside turning1 as shown by ,fig4 #cf4 ,the cutting end of a solid type of tool is forged approximately at right angles to the body or shank1 and the top surface is ground to slope away from the working part w of the cutting edge1 as with practically all turning tools4 ,the front part or flank1 f is also ground away to give the edge clearance4 ,this type of tool is clamped in the toolpost with the body about parallel with the lathe spindle1 and ordinarily the cutting edge would be about as high as the center of the hole1 or a little below1 if anything4 ,when starting a cut1 the tool is brought up to the work by moving the carriage and it is then adjusted radially to get the right depth of cut1 by shifting the cross-slide4 ,the power feed for the carriage is then used1 the tool feeding back through the hole as indicated by the arrow1 ,fig4 #cd4 ,in this case1 as with all turning operations1 the first cut should be deep enough to remove the hard outer scale at every part of the hole4 ,usually a rough-cored hole is so much smaller than the finished size that several cuts are necessary2 in any case1 the last or finishing cut should be very light to prevent the tool from springing away from the work1 so that the hole will be as true as possible4 ,boring tools1 particularly for small holes1 are not as rigid as those used for outside turning1 as the tool has to be small enough to enter the hole and for this reason comparatively light cuts have to be taken4 ,when boring a small hole1 the largest tool that will enter it without interference should be used to get the greatest rigidity possible4 ,illustration3 ,fig4 #cg 7,a7 ,setting ,outside ,calipers4 7,b7 ,transferring ,measurements to ,inside ,calipers4 7,c7 ,micrometer ,gage ,measuring ,bored ,holes4--,the diameters of small holes that are being bored are usually measured with inside calipers or standard gages4 ,if the pulley were being bored to fit over some shaft1 the diameter of the shaft would first be measured by using outside calipers1 as shown at ,a1 ,fig4 #cg1 the measuring points of the calipers being adjusted until they just made contact with the shaft when passed over it4 ,the inside calipers are then set as at ,b to correspond with the size of the shaft1 and the hole is bored just large enough to admit the inside calipers easily4 ,very accurate measurements can be made with calipers1 but to become expert in their use requires experience4 ,some mechanics never become proficient in the art of calipering because their hands are heavy and they lack the sensitiveness and delicacy of touch that is necessary4 ,for large holes1 a gage ,c is often used1 the length l being adjusted to the diameter desired4 ,small holes are often bored to fit hardened steel plug gages 7,fig4 #ch71 the cylindrical measuring ends of which are made with great accuracy to standard sizes4 ,this type of gage is particularly useful when a number of holes have to be bored to the same size1 all holes being made just large enough to fit the gage without any perceptible play4 ,illustration3 ,fig4 #ch4 ,standard ,plug ,gage ,setting ,work in the ,chuck4--,when setting a part in a chuck1 care should be taken to so locate it that every surface to be turned will be true when machined to the finished size4 ,as a simple illustration1 let us assume that the hole through the cast-iron disk1 ,fig4 #ci1 has been cored considerably out of center1 as shown4 ,if the work is set by the outside surface ,s1 as it would be ordinarily1 the hole is so much out of center that it will not be true when bored to the finished size1 as indicated by the dotted lines4 ,on the other hand1 if the rough hole is set true1 the outside cannot be finished all over1 without making the diameter too small1 when it is finally turned4 ,in such a case1 the casting should be shifted1 as shown by the arrow1 to divide the error between the two surfaces1 both of which can then be turned as shown by the dotted lines in the view to the right4 ,this principle of dividing the error when setting work can often be applied in connection with turning and boring4 ,after a casting or other part has been set true by the most important surface1 all other surfaces which require machining should be tested to make sure that they all can be finished to the proper size4 ,inaccuracy from ,pressure of ,chuck ,jaws4--,work that is held in a chuck is sometimes sprung out of shape by the pressure of the chuck jaws so that when the part is bored or turned1 the finished surfaces are untrue after the jaws are released and the work has resumed its normal shape4 ,this applies more particularly to frail parts1 such as rings1 thin cylindrical parts1 etc4 ,occasionally the distortion can be prevented by so locating the work with relation to the chuck jaws that the latter bear against a rigid part4 ,when the work cannot be held tightly enough for the roughing cuts without springing it1 the jaws should be released somewhat before taking the finishing cut1 to permit the part to spring back to its natural shape4 ,illustration3 ,fig4 #ci4 ,diagram ,illustrating ,importance of ,setting ,work with ,reference to ,surfaces to be ,turned ,illustration3 ,fig4 #dj4 ,drilling in the ,lathe ,drilling and ,reaming4--,when a hole is to be bored from the solid1 it is necessary to drill a hole before a boring tool can be used4 ,one method of drilling in the lathe is to insert an ordinary twist drill in a holder or socket ,s1 ,fig4 #dj1 which is inserted in the tailstock spindle in place of the center4 ,the drill is then fed through the work by turning the handle n and feeding the spindle outward as shown by the arrow4 ,before beginning to drill1 it is well to turn a conical spot or center for the drill point so the latter will start true4 ,this is often done by using a special tool having a point like a flat drill4 ,this tool is clamped in the toolpost with the point at the same height as the lathe centers4 ,it is then fed against the center of the work and a conical center is turned4 ,if the drill were not given this true starting point1 it probably would enter the work more or less off center4 ,drills can also be started without turning a center by bringing the square end or butt of a tool-shank held in the toolpost in contact with the drill near the cutting end4 ,if the point starts off center1 thus causing the drill to wobble1 the stationary tool-shank will gradually force or bump it over to the center4 ,illustration3 ,fig4 #da4 ,flat ,drill and ,holder ,small holes are often finished in the lathe by drilling and reaming without the use of a boring tool4 ,the form of drill that is used quite extensively for drilling cored holes in castings is shown in ,fig4 #da1 at ,a4 ,this drill is flat and the right end has a large center hole for receiving the center of the tailstock4 ,to prevent the drill from turning1 a holder ,b1 having a slot s in its end through which the drill passes1 is clamped in the toolpost1 as at ,c4 ,this slot should be set central with the lathe centers1 and the drill1 when being started1 should be held tightly in the slot by turning or twisting it with a wrench as indicated in the end view at ,d2 this steadies the drill and causes it to start fairly true even though the cored hole runs out considerably4 ,another style of tool for enlarging cored holes is shown in ,fig4 #db1 at ,a4 ,this is a rose chucking reamer1 having beveled cutting edges on the end and a cylindrical body1 which fits closely in the reamed hole1 thus supporting and guiding the cutting end4 ,the reamer shown at ,b is a fluted type with cutting edges that extend from a to b2 it is used for finishing holes and the drill or rose reamer preceding it should leave the hole very close to the required size4 ,these reamers are held while in use in a socket inserted in the tailstock spindle1 as when using a twist drill4 ,illustration3 ,fig4 #db4 ,rose and ,fluted ,reamers ,holding ,work on ,faceplate4--,some castings or forgings are so shaped that they cannot be held in a chuck very well1 or perhaps not at all1 and work of this kind is often clamped to a faceplate which is usually larger than the faceplate used for driving parts that are turned between the centers4 ,an example of faceplate work is shown in ,fig4 #dc4 ,this is a rectangular-shaped casting having a round boss or projection1 the end e of which is to be turned parallel with the back face of the casting previously finished on a planer4 ,a rough cored hole through the center of the boss also needs to be bored true4 ,the best way to perform this operation in the lathe would be to clamp the finished surface of the casting directly against the faceplate by bolts and clamps a1 b1 c1 and d1 as shown2 the work would then be turned just as though it were held in a chuck4 ,by holding the casting in this way1 face e will be finished parallel with the back surface because the latter is clamped directly against the true-running surface of the faceplate4 ,if a casting of this shape were small enough it could also be held in the jaws of an independent chuck1 but if the surface e needs to be exactly parallel with the back face1 it is better to clamp the work to the faceplate4 ,most lathes have two faceplates3 ,one of small diameter used principally for driving work turned between centers1 and a large one for holding heavy or irregularly shaped pieces2 either of these can be screwed onto the spindle1 and the large faceplate has a number of slots through which clamping bolts can be inserted4 ,illustration3 ,fig4 #dc4 ,casting ,clamped to ,faceplate for ,turning and ,boring ,the proper way to clamp a piece to the faceplate depends1 of course1 largely on its shape and the location of the surface to be machined1 but in any case it is necessary to hold it securely to prevent any shifting after a cut is started4 ,sometimes castings can be held by inserting bolts through previously drilled holes1 but when clamps are used in connection with the bolts1 their outer ends are supported by hardwood or metal blocks which should be just high enough to make the clamp bear evenly on the work4 ,when deep roughing cuts have to be taken1 especially on large diameters1 it is well to bolt a piece to the faceplate and against one side of the casting1 as at ,d1 to act as a driver and prevent the work from shifting2 but a driver would not be needed in this particular case4 ,of course a faceplate driver is always placed to the rear1 as determined by the direction of rotation1 because the work tends to shift backward when a cut is being taken4 ,if the surface which is clamped against the faceplate is finished as in this case1 the work will be less likely to shift if a piece of paper is placed between it and the faceplate4 ,illustration3 ,fig4 #dd4 ,cast ,elbow held on ,angle-plate attached to ,faceplate ,work mounted on the faceplate is generally set true by some surface before turning4 ,as the hole in this casting should be true with the round boss1 the casting is shifted on the faceplate until the rough outer surface of the boss runs true2 the clamps which were previously set up lightly are then tightened4 ,the face e is first turned by using a round-nosed tool4 ,this tool is then replaced by a boring tool and the hole is finished to the required diameter4 ,if the hole being bored is larger than the central hole in the faceplate1 the casting should be clamped against parallel pieces1 and not directly against the faceplate1 to provide clearance for the tool when it reaches the inner end of the hole and prevent it from cutting the faceplate4 ,the parallel pieces should be of the same thickness and be located near the clamps to prevent springing the casting4 ,application of ,angle-plate to ,faceplate4--,another example of faceplate work is shown in ,fig4 #dd4 ,this is a cast-iron elbow ,e1 the two flanges of which are to be faced true and square with each other4 ,the shape of this casting is such that it would be very difficult to clamp it directly to the faceplate1 but it is easily held on an angle-plate ,p1 which is bolted to the faceplate4 ,the two surfaces of this angle-plate are square with each other so that when one flange of the elbow is finished and bolted against the angle-plate1 the other will be faced square4 ,when setting up an angle-plate for work of this kind1 the distance from its work-holding side to the center of the faceplate is made equal to the distance d between the center of one flange and the face of the other1 so that the flange to be faced will run about true when bolted in place4 ,as the angle-plate and work are almost entirely on one side of the faceplate1 a weight ,w is attached to the opposite side for counterbalancing4 ,very often weights are also needed to counterbalance offset parts that are bolted directly to the faceplate4 ,the necessity of counterbalancing depends somewhat upon the speed to be used for turning4 ,if the surface to be machined is small in diameter so that the lathe can be run quite rapidly1 any unbalanced part should always be counterbalanced4 ,sometimes it is rather difficult to hold heavy pieces against the vertical surface of the faceplate while applying the clamps1 and occasionally the faceplate is removed and placed in a horizontal position on the bench2 the work can then be located about right1 and after it is clamped1 the faceplate is placed on the lathe spindle by the assistance of a crane4 ,special faceplate jaws1 such as the one shown to the right in ,fig4 #cc1 can often be used to advantage for holding work on large faceplates4 ,three or four of these jaws are bolted to the faceplate which is converted into a kind of independent chuck4 ,these faceplate jaws are especially useful for holding irregularly shaped parts1 as the different jaws can be located in any position4 ,supporting ,outer ,end of ,chucked ,work4--,fig4 #de shows how the tailstock center is sometimes used for supporting the outer end of a long casting1 the opposite end of which is held in a chuck4 ,this particular casting is to be turned and bored to make a lining for the cylinder of a locomotive in order to reduce the diameter of the cylinder which has been considerably enlarged by re-boring a number of times4 ,these bushings are rough-turned on the outside while the outer end is supported by the cross-shaped piece or spider which forms a center-bearing for the tailstock4 ,this spider has set screws in the flanged ends of the arms1 which are tightened against the inner surface of the casting and are adjusted one way or the other in order to locate it in a concentric position4 ,after roughing the outside1 the inside is bored to the finish size2 then centered disks1 which fit into the bore1 are placed in the ends of the bushing and the latter is finish-turned4 ,the object in rough turning the outside prior to boring is to avoid the distortion which might occur if this hard outer surface were removed last4 ,illustration3 ,fig4 #de4 ,rough ,turning a ,cylinder ,lining--,note ,method of ,supporting ,outer ,end ,boring ,large ,castings in the ,lathe4--,an ordinary engine lathe is sometimes used for boring engine or pump cylinders1 linings1 etc41 which are too large to be held in the chuck or on a faceplate1 and must be attached to the lathe carriage4 ,as a rule1 work of this class is done in a special boring machine 7see ,horizontal ,boring ,machines71 but if such a machine is not available1 it may be necessary to use a lathe4 ,there are two general methods of boring4 ,fig4 #df shows how the lining illustrated in ,fig4 #de is bored in a large engine lathe4 ,the casting is held in special fixtures which are attached to the lathe carriage1 and the boring-bar is rotated by the lathe spindle4 ,the tool-head of this boring-bar carries two tools located #ahj degrees apart and it is fed along the bar by a star-feed mechanism shown attached to the bar and the tailstock spindle4 ,each time the bar revolves1 the star wheel strikes a stationary pin and turns the feed-screw which1 as the illustration shows1 extends along a groove cut in one side of the bar4 ,this feed-screw passes through a nut attached to the tool-head so that the latter is slowly fed through the bore4 ,when using a bar of this type1 the carriage1 of course1 remains stationary4 ,illustration3 ,fig4 #df4 ,boring a ,cylinder ,lining in an ,ordinary ,engine ,lathe ,cylindrical parts attached to the carriage can also be bored by using a plain solid bar mounted between the centers4 ,the bar must be provided with a cutter for small holes or a tool-head for larger diameters 7preferably holding two or more tools7 and the boring is done by feeding the carriage along the bed by using the regular power feed of the lathe4 ,a symmetrically shaped casting like a bushing or lining is often held upon wooden blocks bolted across the carriage4 ,these are first cut away to form a circular seat of the required radius1 by using the boring-bar and a special tool having a thin curved edge4 ,the casting is then clamped upon these blocks by the use of straps and bolts1 and if the curved seats were cut to the correct radius1 the work will be located concentric with the boring-bar4 ,when using a boring-bar of this type1 the bar must be long enough to allow the part being bored to feed from one side of the cutter-head to the other1 the cutter-head being approximately in a central location4 ,illustration3 ,fig4 #dg4 ,method of ,setting ,circle on ,work ,concentric with ,lathe ,spindle ,boring ,holes to a ,given ,center ,distance4--,in connection with faceplate work1 it is often necessary to bore two or more holes at a given distance apart4 ,the best method of doing this may depend upon the accuracy required4 ,for ordinary work sometimes two or more circles ,a and ,b 7,fig4 #dg7 are drawn upon the part to be bored1 in the position for the holes2 the piece is then clamped to the faceplate and one of the circles is centered with the lathe spindle by testing it with a pointer ,c held in the toolpost2 that is1 when the pointer follows the circle as the work is turned1 evidently the circle is concentric with the spindle4 ,the hole is then drilled and bored4 ,the other circle is then centered in the same way for boring the second hole4 ,as will be seen1 the accuracy of this method depends first1 upon the accuracy with which the circles were laid out1 and second2 upon the care taken in setting them concentric4 ,for a more accurate way of locating parts for boring1 see ,use of ,center ,indicator and ,locating ,work by the ,button ,method4 ,turning ,brass1 ,bronze and ,copper4--,when turning soft yellow brass1 a tool should be used having very little or no slope or rake on the top surface against which the chip bears1 and for plain cylindrical turning1 the point of the tool is drawn out quite thin and rounded1 by grinding1 to a radius of about #a_/h or #c_/af inch4 ,if a tool having very much top slope is used for brass1 there is danger of its gouging into the metal1 especially if the part being turned is at all flexible4 ,the clearance angle of a brass tool is usually about #ab or #ad degrees1 which is #c or #d degrees greater than the clearance for steel turning tools4 ,most brass is easily turned1 as compared with steel1 and for that reason this increase in clearance is desirable1 because it facilitates feeding the tool into the metal1 especially when the carriage and cross-slide movements are being controlled by hand as when turning irregular shapes4 ,the speed for turning soft brass is much higher than for steel1 being ordinarily between #aej and #bjj feet per minute4 ,when turning phosphor1 tobin or other tough bronze compositions1 the tool should be ground with rake the same as for turning steel1 and lard oil is sometimes used as a lubricant4 ,the cutting speed for bronzes varies from #ce or #dj to #hj feet per minute1 owing to the difference in the composition of bronze alloys4 ,turning tools for copper are ground with a little more top rake than is given steel turning tools1 and the point should be slightly rounded4 ,it is important to have a keen edge1 and a grindstone is recommended for sharpening copper turning tools4 ,milk is generally considered the best lubricant to use when turning copper4 ,the speed can be nearly as fast as for brass4 ,machining ,aluminum4--,tools for turning aluminum should have acute cutting angles4 ,after rough-grinding the tool1 it is advisable to finish sharpening the cutting edge on a grindstone or with an oilstone for fine work1 as a keen edge is very essential4 ,high speeds and comparatively light cuts are recommended4 ,the principal difficulty in the machining of aluminum and aluminum alloys is caused by the clogging of the chips1 especially when using such tools as counterbores and milling cutters4 ,this difficulty can be avoided largely by using the right kind of cutting lubricant4 ,soap-water and kerosene are commonly employed4 ,the latter enables a fine finish to be obtained1 provided the cutting tool is properly ground4 ,the following information on this subject represents the experience of the ,brown-,lipe ,gear ,co41 where aluminum parts are machined in large quantities3 ,for finishing bored holes1 a bar equipped with cutters has been found more practicable than reamers4 ,the cutters used for machining #d-;inch holes have a clearance of from #bj to #bb degrees and no rake or slope on the front faces against which the chips bear4 ,the roughing cutters for this work have a rather sharp nose1 being ground on the point to a radius of about #c_/cb inch1 but for securing a smooth surface1 the finishing tools are rounded to a radius of about #c_/d inch4 ,the cutting speed1 as well as the feed1 for machining aluminum is from #ej to #fj per cent faster than the speeds and feeds for cast iron4 ,the lubricant used by this company is composed of one part aqualine and #bj parts water4 ,this lubricant not only gives a smooth finish but preserves a keen cutting edge and enables tools to be used much longer without grinding4 ,formerly1 a lubricant composed of one part of high-grade lard oil and one part of kerosene was used4 ,this mixture costs approximately #cj cents per gallon1 whereas the aqualine and water mixture now being used costs less than #d cents per gallon1 and has proved more effective than the lubricant formerly employed4 ,,chapter ,,ii ,,lathe ,,turning ,,tools ,,and ,,cutting ,,speeds ,notwithstanding the fact that a great variety of work can be done in the lathe1 the number of turning tools required is comparatively small4 ,fig4 #a shows the forms of tools that are used principally1 and typical examples of the application of these various tools are indicated in ,fig4 #b4 ,the reference letters used in these two illustrations correspond for tools of the same type1 and both views should be referred to in connection with the following description4 ,turning ,tools for ,general ,work4--,the tool shown at ,a is the form generally used for rough turning1 that is for taking deep cuts when considerable metal has to be removed4 ,at ,b a tool of the same type is shown1 having a bent end which enables it to be used close up to a shoulder or surface s that might come in contact with the tool-rest if the straight form were employed4 ,tool ,c1 which has a straight cutting end1 is used on certain classes of work for taking light finishing cuts1 with a coarse feed4 ,this type of tool has a flat or straight cutting edge at the end1 and will leave a smooth finish even though the feed is coarse1 provided the cutting edge is set parallel with the tool's travel so as to avoid ridges4 ,broad-nosed tools and wide feeds are better adapted for finishing cast iron than steel4 ,when turning steel1 if the work is at all flexible1 a broad tool tends to gouge into it and for this reason round-nosed tools and finer feeds are generally necessary4 ,a little experience in turning will teach more on this point than a whole chapter on the subject4 ,illustration3 ,fig4 #a4 ,set of ,lathe ,turning ,tools for ,general ,work ,illustration3 ,fig4 #b4 ,views illustrating ,use of ,various ,types of ,lathe ,tools ,the side-tools shown at ,d and ,e are for facing the ends of shafts1 collars1 etc4 ,the first tool is known as a right side-tool because it operates on the right end or side of a shaft or collar1 whereas the left side-tool ,e is used on the opposite side1 as shown in ,fig4 #b4 ,side-tools are also bent to the right or left because the cutting edge of a straight tool cannot always be located properly for facing certain surfaces4 ,a bent right side-tool is shown at ,f4 ,a form of tool that is frequently used is shown at ,g2 this is known as a parting tool and is used for severing pieces and for cutting grooves1 squaring corners1 etc4 ,the same type of tool having a bent end is shown at ,h 7,fig4 #b7 severing a piece held in the chuck4 ,work that is held between centers should not be entirely severed with a parting tool unless a steadyrest is placed between the tool and faceplate1 as otherwise the tool may be broken by the springing of the work just before the piece is cut in two4 ,it should be noted that the sides of this tool slope inward back of the cutting edge to provide clearance when cutting in a narrow groove4 ,at ,i a thread tool is shown for cutting a ,u4 ,s4 standard thread4 ,this thread is the form most commonly used in this country at the present time4 ,a tool for cutting a square thread is shown at ,j4 ,this is shaped very much like a parting tool except that the cutting end is inclined slightly to correspond with the helix angle of the thread1 as explained in ,chapter ,,iv1 which contains descriptions of different thread forms and methods of cutting them4 ,internal thread tools are shown at ,k and ,l for cutting ,u4 ,s4 standard and square threads in holes4 ,it will be seen that these tools are somewhat like boring tools excepting the ends which are shaped to correspond with the thread which they are intended to cut4 ,illustration3 ,fig4 #c4 ,turning ,tool with ,inserted ,cutter ,a tool for turning brass is shown at ,m4 ,brass tools intended for general work are drawn out quite thin and they are given a narrow rounded point4 ,the top of the brass tool is usually ground flat or without slope as otherwise it tends to gouge into the work1 especially if the latter is at all flexible4 ,the end of a brass tool is sometimes ground with a straight cutting edge for turning large rigid work1 such as brass pump linings1 etc41 so that a coarse feed can be used without leaving a rough surface4 ,the tools at ,n and ,o are for boring or finishing drilled or cored holes4 ,two sizes are shown1 which are intended for small and large holes1 respectively4 ,the different tools referred to in the foregoing might be called the standard types because they are the ones generally used1 and as ,fig4 #b indicates1 they make it possible to turn an almost endless variety of forms4 ,occasionally some special form of tool is needed for doing odd jobs1 having1 perhaps1 an end bent differently or a cutting edge shaped to some particular form4 ,tools of the latter type1 which are known as form tools1 are sometimes used for finishing surfaces that are either convex1 concave1 or irregular in shape4 ,the cutting edges of these tools are carefully filed or ground to the required shape1 and the form given the tool is reproduced in the part turned4 ,ornamental or other irregular surfaces can be finished very neatly by the use of such tools4 ,it is very difficult1 of course1 to turn convex or concave surfaces with a regular tool2 in fact1 it would not be possible to form a true spherical surface1 for instance1 without special equipment1 because the tool could not be moved along a true curve by simply using the longitudinal and cross feeds4 ,form tools should be sharpened by grinding entirely on the top surface1 as any grinding on the end or flank would alter the shape of the tool4 ,illustration3 ,fig4 #d4 ,heavy ,inserted-cutter ,turning ,tool ,tool-holders with ,inserted ,cutters4--,all of the tools shown in ,fig4 #a are forged from the bar1 and when the cutting ends have been ground down considerably it is necessary to forge a new end4 ,to eliminate the expense of this continual dressing of tools and also to effect a great reduction in the amount of tool steel required1 tool-holders having small inserted cutters are used in many shops4 ,a tool-holder of this type1 for outside turning1 is shown in ,fig4 #c4 ,the cutter ,c is held in a fixed position by the set-screw shown1 and it is sharpened1 principally1 by grinding the end1 except when it is desired to give the top of the cutter a different slope from that due to its angular position4 ,another inserted-cutter turning tool is shown in ,fig4 #d1 which is a heavy type intended for roughing4 ,the cutter in this case has teeth on the rear side engaging with corresponding teeth cut in the clamping block which is tightened by a set-screw on the side opposite that shown4 ,with this arrangement1 the cutter can be adjusted upward as the top is ground away4 ,illustration3 ,fig4 #e4 ,parting ,tool with ,inserted ,blade ,illustration3 ,fig4 #f4 ,boring ,tool with ,inserted ,cutter and ,adjustable ,bar ,a parting tool of the inserted blade type is shown in ,fig4 #e4 ,the blade ,b is clamped by screw ,s and also by the spring of the holder when the latter is clamped in the toolpost4 ,the blade can1 of course1 be moved outward when necessary4 ,fig4 #f shows a boring tool consisting of a holder ,h1 a bar ,b that can be clamped in any position1 and an inserted cutter ,c4 ,with this type of boring tool1 the bar can be extended beyond the holder just far enough to reach through the hole to be bored1 which makes the tool very rigid4 ,a thread tool of the holder type is shown in ,fig4 #g4 ,the angular edge of the cutter ,c is accurately ground by the manufacturers1 so that the tool is sharpened by simply grinding it flat on the top4 ,as the top is ground away1 the cutter is raised by turning screw ,s1 which can also be used for setting the tool to the proper height4 ,the ,position of ,turning ,tools4--,the production of accurate lathe work depends partly on the condition of the lathe used and also on the care and judgment exercised by the man operating it4 ,even though a lathe is properly adjusted and in good condition otherwise1 errors are often made which are due to other causes which should be carefully avoided4 ,if the turning tool is clamped so that the cutting end extends too far from the supporting block1 the downward spring of the tool1 owing to the thrust of the cut1 sometimes results in spoiled work1 especially when an attempt is made to turn close to the finished size by taking a heavy roughing cut4 ,suppose the end of a cylindrical part is first reduced for a short distance by taking several trial cuts until the diameter d1 ,fig4 #h1 is slightly above the finished size and the power feed is then engaged4 ,when the tool begins to take the full depth e of the cut1 the point1 which ordinarily would be set a little above the center1 tends to spring downward into the work1 and if there were considerable springing action1 the part would probably be turned below the finished size1 the increased reduction beginning at the point where the full cut started4 ,illustration3 ,fig4 #g4 ,threading ,tool ,this springing action1 as far as the tool is concerned1 can be practically eliminated by locating the tool so that the distance ,a between the tool-block and cutting end1 or the overhang1 is as short as possible4 ,even though the tool has little overhang it may tilt downward because the toolslide is loose on its ways1 and for this reason the slide should have a snug adjustment that will permit an easy movement without unnecessary play4 ,the toolslides of all lathes are provided with gibs which can be adjusted by screws to compensate for wear1 or to secure a more rigid bearing4 ,illustration3 ,fig4 #h4 ,to avoid springing1 ,overhang ,a of ,tool should not be ,excessive ,when roughing cuts are to be taken1 the tool should be located so that any change in its position which might be caused by the pressure of the cut will not spoil the work4 ,this point is illustrated at ,a in ,fig4 #i4 ,suppose the end of a rod has been reduced by taking a number of trial cuts1 until it is #a_/cb inch above the finished size4 ,if the power feed is then engaged with the tool clamped in an oblique position1 as shown1 when the full cut is encountered at c1 the tool1 unless very tightly clamped1 may be shifted backward by the lateral thrust of the cut1 as indicated by the dotted lines4 ,the point will then begin turning smaller than the finished size and the work will be spoiled4 ,to prevent any change of position1 it is good practice1 especially when roughing1 to clamp the tool square with the surface being turned1 or in other words1 at right angles to its direction of movement4 ,occasionally1 however1 there is a decided advantage in having the tool set at an angle4 ,for example1 if it is held about as shown at ,b1 when turning the flange casting ,c1 the surfaces s and s#a can be finished without changing the tool's position4 ,cylindrical and radial surfaces are often turned in this way in order to avoid shifting the tool1 especially when machining parts in quantity4 ,tool ,grinding4--,in the grinding of lathe tools there are three things of importance to be considered3 ,first1 the cutting edge of the tool 7as viewed from the top7 needs to be given a certain shape2 second1 there must be a sufficient amount of clearance for the cutting edge2 and third1 tools1 with certain exceptions1 are ground with a backward slope or a side slope1 or with a combination of these two slopes on that part against which the chip bears when the tool is in use4 ,illustration3 ,fig4 #i4 7,a7 ,the ,way in which ,tool is sometimes displaced by ,thrust of ,cut1 when set at an ,angle4 7,b7 ,tool ,set for ,finishing both ,cylindrical and ,radial ,surfaces ,in ,fig4 #aj a few of the different types of tools which are used in connection with lathe work are shown4 ,this illustration also indicates the meaning of the various terms used in tool grinding4 ,as shown1 the clearance of the tool is represented by the angle alpha1 the back slope is represented by the angle beta1 and the side slope by the angle gamma4 ,the angle delta for a tool without side slope is known as the lip angle or the angle of keenness4 ,when1 however1 the tool has both back and side slopes1 this lip angle would more properly be the angle between the flank f and the top of the tool1 measured diagonally along a line z--z4 ,it will be seen that the lines ,a--,b and ,a--,c from which the angles of clearance and back slope are measured are parallel with the top and sides of the tool shank1 respectively4 ,for lathe tools1 however1 these lines are not necessarily located in this way when the tool is in use1 as the height of the tool point with relation to the work center determines the position of these lines1 so that the effective angles of back slope1 clearance and keenness are changed as the tool point is lowered or raised4 ,the way the position of the tool affects these angles will be explained later4 ,illustration3 ,fig4 #aj4 ,illustration showing the ,meaning of ,terms used in ,tool ,grinding as applied to ,tools of ,different ,types ,while tools must1 of necessity1 be varied considerably in shape to adapt them to various purposes1 there are certain underlying principles governing their shape which apply generally2 so in what follows we shall not attempt to explain in detail just what the form of each tool used on the lathe should be1 as it is more important to understand how the cutting action of the tool and its efficiency is affected when it is improperly ground4 ,when the principle is understood1 the grinding of tools of various types and shapes is comparatively easy4 ,illustration3 ,fig4 #aa4 ,plan ,view of ,lathe ,turning and ,threading ,tools ,shape or ,contour of ,cutting ,edge4--,in the first place we shall consider the shape or contour of the cutting edge of the tool as viewed from the top1 and then take up the question of clearance and slope1 the different elements being considered separately to avoid confusion4 ,the contour of the cutting edge depends primarily upon the purpose for which the tool is intended4 ,for example1 the tool ,a1 in ,fig4 #aa1 where a plan view of a number of different lathe tools is shown1 has a very different shape from that of1 say1 tool ,d1 as the first tool is used for rough turning1 while tool ,d is intended for cutting grooves or severing a turned part4 ,similarly1 tool ,e is ,v-shaped because it is used for cutting ,v-threads4 ,tools ,a1 ,b and ,c1 however1 are regular turning tools2 that is1 they are all intended for turning plain cylindrical surfaces1 but the contour of the cutting edges varies considerably1 as shown4 ,in this case it is the characteristics of the work and the cut that are the factors which determine the shape4 ,to illustrate1 tool ,a is of a shape suitable for rough-turning large and rigid work1 while tool ,b is adapted for smaller and more flexible parts4 ,the first tool is well shaped for roughing because experiments have shown that a cutting edge of a large radius is capable of higher cutting speed than could be used with a tool like ,b1 which has a smaller point4 ,this increase in the cutting speed is due to the fact that the tool ,a removes a thinner chip for a given feed than tool ,b2 therefore1 the speed may be increased without injuring the cutting edge to the same extent4 ,if1 however1 tool ,a were to be used for turning a long and flexible part1 chattering might result2 consequently1 a tool ,b having a point with a smaller radius would be preferable1 if not absolutely necessary4 ,the character of the work also affects the shape of tools4 ,the tool shown at ,c is used for taking light finishing cuts with a wide feed4 ,obviously1 if the straight or flat part of the cutting edge is in line with the travel of the tool1 the cut will be smooth and free from ridges1 even though the feed is coarse1 and by using a coarse feed the cut is taken in less time2 but such a tool cannot be used on work that is not rigid1 as chattering would result4 ,therefore1 a smaller cutting point and a reduced feed would have to be employed4 ,tools with broad flat cutting edges and coarse feeds are often used for taking finishing cuts in cast iron1 as this metal offers less resistance to cutting than steel1 and is less conducive to chattering4 ,the shape of a tool 7as viewed from the top7 which is intended for a more specific purpose than regular turning1 can be largely determined by simply considering the tool under working conditions4 ,this point may be illustrated by the parting tool ,d which1 as previously stated1 is used for cutting grooves1 squaring corners1 etc4 ,evidently this tool should be widest at the cutting edge2 that is1 the sides d should have a slight amount of clearance so that they will not bind as the tool is fed into a groove4 ,as the tool at ,e is for cutting a ,v-thread1 the angle alpha between its cutting edges must equal the angle between the sides of a ,v-thread1 or #fj degrees4 ,the tool illustrated at ,f is for cutting inside square threads4 ,in this case the width w should be made equal to one-half the pitch of the thread 7or slightly greater to provide clearance for the screw71 and the sides should be given a slight amount of side clearance1 the same as with the parting tool ,d4 ,so we see that the outline of the tool1 as viewed from the top1 must conform to and be governed by its use4 ,direction of ,top ,slope for ,turning ,tools4--,aside from the question of the shape of the cutting edge as viewed from the top1 there remains to be determined the amount of clearance that the tool shall have1 and also the slope 7and its direction7 of the top of the tool4 ,by the top is meant that surface against which the chip bears while it is being severed4 ,it may be stated1 in a general way1 that the direction in which the top of the tool should slope should be away from what is to be the working part of the cutting edge4 ,for example1 the working edge of a roughing tool ,a 7,fig4 #aa71 which is used for heavy cuts1 would be1 practically speaking1 between points a and b1 or1 in other words1 most of the work would be done by this part of the cutting edge2 therefore the top should slope back from this part of the edge4 ,obviously1 a tool ground in this way will have both a back and a side slope4 ,when most of the work is done on the point or nose of the tool1 as1 for example1 with the lathe finishing tool ,c which takes light cuts1 the slope should be straight back from the point or cutting edge a--b4 ,as the side tool shown in ,fig4 #aj does its cutting along the edge a--b1 the top is given a slope back from this edge as shown in the end view4 ,this point should be remembered1 for when the top slopes in the right direction1 less power is required for cutting4 ,tools for certain classes of work1 such as thread tools1 or those for turning brass or chilled iron1 are ground flat on top1 that is1 without back or side slope4 ,clearance for the ,cutting ,edge4--,in order that the cutting edge may work without interference1 it must have clearance2 that is1 the flank f 7,fig4 #aj7 must be ground to a certain angle alpha so that it will not rub against the work and prevent the cutting edge from entering the metal4 ,this clearance should be just enough to permit the tool to cut freely4 ,a clearance angle of eight or ten degrees is about right for lathe turning tools4 ,the back slope of a tool is measured from a line ,a--,b which is parallel to the shank1 and the clearance angle1 from a line ,a--,c at right angles to line ,a--,b4 ,these lines do not1 however1 always occupy this position with relation to the tool shank when the tool is in use4 ,as shown to the left in ,fig4 #ab1 the base line ,a--,b for a turning tool in use intersects with the point of the tool and center of the work1 while the line ,a--,c remains at right angles to the first4 ,it will be seen1 then1 that by raising the tool1 as shown to the right1 the effective clearance angle alpha will be diminished1 whereas lowering it1 as shown by the dotted lines1 will have the opposite effect4 ,a turning tool for brass or other soft metal1 particularly where considerable hand manipulation is required1 could advantageously have a clearance of twelve or fourteen degrees1 as it would then be easier to feed the tool into the metal2 but1 generally speaking1 the clearance for turning tools should be just enough to permit them to cut freely4 ,excessive clearance weakens the cutting edge and may cause it to crumble under the pressure of the cut4 ,illustration3 ,fig4 #ab4 ,illustrations showing how ,effective ,angles of ,slope and ,clearance change as ,tool is raised or lowered ,angle of ,tool-point and ,amount of ,top ,slope4--,the lip angle or the angle of keenness delta 7,fig4 #aj7 is another important consideration in connection with tool grinding1 for it is upon this angle that the efficiency of the tool largely depends4 ,by referring to the illustration it will be seen that this angle is governed by the clearance and the slope beta1 and as the clearance remains practically the same1 it is the slope which is varied to meet different conditions4 ,now1 the amount of slope a tool should have depends on the work for which it is intended4 ,if1 for example1 a turning tool is to be used for roughing medium or soft steel1 it should have a back slope of about eight degrees and a side slope ranging from fourteen to twenty degrees1 while a tool for cutting very hard steel should have a back slope of about five degrees and a side slope of nine degrees4 ,illustration3 ,fig4 #ac4 7,a7 ,blunt ,tool for ,turning ,hard ,steel4 7,b7 ,tool-point ,ground to give ,keenness ,the reason for decreasing the slope and thus increasing the lip angle for harder metals is to give the necessary increased strength to the cutting edge to prevent it from crumbling under the pressure of the cut4 ,the tool illustrated at ,a1 ,fig4 #ac1 is much stronger than it would be if ground as shown at ,b1 as the former is more blunt4 ,if a tool ground as at ,a1 however1 were used for cutting very soft steel1 there would be a greater chip pressure on the top and1 consequently1 a greater resistance to cutting1 than if a keener tool had been employed2 furthermore the cutting speed would have to be lower1 which is of even greater importance than the chip pressure2 therefore1 the lip angle1 as a general rule1 should be as small as possible without weakening the tool so that it cannot do the required work4 ,in order to secure a strong and well-supported cutting edge1 tools used for turning very hard metal1 such as chilled rolls1 etc41 are ground with practically no slope and with very little clearance4 ,brass tools1 while given considerable clearance1 as previously stated1 are ground flat on top or without slope2 this is not done1 however1 to give strength to the cutting edge1 but rather to prevent the tool from gouging into the work1 which it is likely to do if the part being turned is at all flexible and the tool has top slope4 ,experiments conducted by ,mr4 ,f4 ,w4 ,taylor to determine the most efficient form for lathe roughing tools showed that the nearer the lip angle approached sixty-one degrees1 the higher the cutting speed4 ,this1 however1 does not apply to tools for turning cast iron1 as the latter will work more efficiently with a lip angle of about sixty-eight degrees4 ,this is doubtless because the chip pressure1 when turning cast iron1 comes closer to the cutting edge which should1 therefore1 be more blunt to withstand the abrasive action and heat4 ,of course1 the foregoing remarks concerning lip angles apply more particularly to tools used for roughing4 ,illustration3 ,fig4 #ad4 ,grinding the ,top and ,flank of a ,turning ,tool ,grinding a ,lathe ,tool4--,the way a turning tool is held while the top surface is being ground is shown to the left in ,fig4 #ad4 ,by inclining the tool with the wheel face1 it will be seen that both the back and side slopes may be ground at the same time4 ,when grinding the flank of the tool it should be held on the tool-rest of the emery wheel or grindstone1 as shown by the view to the right4 ,in order to form a curved cutting edge1 the tool is turned about the face of the stone while it is being ground4 ,this rotary movement can be effected by supporting the inner end of the tool with one hand while the shank is moved to and fro with the other4 ,often a tool which has been ground properly in the first place is greatly misshapen after it has been sharpened a few times4 ,this is usually the result of attempts on the part of the workman to re-sharpen it hurriedly2 for example1 it is easier to secure a sharp edge on the turning tool shown to the left in ,fig4 #ab1 by grinding the flank as indicated by the dotted line1 than by grinding the entire flank4 ,the clearance is1 however1 reduced and the lip angle changed4 ,there is great danger when grinding a tool of burning it or drawing the temper from the fine cutting edge1 and1 aside from the actual shape of the cutting end1 this is the most important point in connection with tool grinding4 ,if a tool is pressed hard against an emery or other abrasive wheel1 even though the latter has a copious supply of water1 the temper will sometimes be drawn4 ,when grinding a flat surface1 to avoid burning1 the tool should frequently be withdrawn from the stone so that the cooling water 7a copious supply of which should be provided7 can reach the surface being ground4 ,a moderate pressure should also be applied1 as it is better to spend an extra minute or two in grinding than to ruin the tool by burning1 in an attempt to sharpen it quickly4 ,of course1 what has been said about burning applies more particularly to carbon steel1 but even self-hardening steels are not improved by being over-heated at the stone4 ,in some shops1 tools are ground to the theoretically correct shape in special machines instead of by hand4 ,the sharpened tools are then kept in the tool-room and are given out as they are needed4 ,cutting ,speeds and ,feeds4--,the term cutting speed as applied to turning operations is the speed in feet per minute of the surface being turned1 or1 practically speaking1 it is equivalent to the length of a chip1 in feet1 which would be turned in one minute4 ,the term cutting speed should not be confused with revolutions per minute1 because the cutting speed depends not only upon the speed of the work but also upon its diameter4 ,the feed of a tool is the amount it moves across the surface being turned for each revolution2 that is1 when turning a cylindrical piece1 the feed is the amount that the tool moves sidewise for each revolution of the work4 ,evidently the time required for turning is governed largely by the cutting speed1 the feed1 and the depth of the cut2 therefore1 these elements should be carefully considered4 ,cutting ,speeds and ,feeds for ,turning ,tools#a ---------------------------------------- -------------------------- ,steel--,standard #g_/h-;inch ,tool ,cast ,iron--,standard #g_/h-;inch ,tool ---------------------------------------- ---------------------- ,speed in ,feet per ,speed in ,feet per ,depth,feed ,minute for a ,tool ,depth,feed ,minute for a ,tool of in which is to last of in which is to last ,cut ,in- #a-a_/b ,hour before ,cut ,in- #a-a_/b ,hour before in ches ,re-grinding in ches ,re-grinding ,in- ------------------- ,in- ------------------- ches ,soft ,medium ,hard ches ,soft ,medium ,hard ,steel ,steel ,steel ,cast ,cast ,cast ,iron ,iron ,iron ---------------------------------------- ------------------ #a_/fd #dgf #bch #ajh #a_/af #abb #fa4b #ce4g #c_/cb #a_/cb #cbe #afb #gc4h #c_/cb #a_/h #hf4d #dc4b #be4b #a_/af #bbb #aaa #ej4d #c_/af #gj4a #ce4a #bj4e #c_/cb #agg #hh4d #dj4b ----------------------------- ----------------------------- #a_/cb #aef #gg4h #de4d #a_/fd #dbj #baj #ie4e #a_/h #a_/af #aab #ef4b #cb4h #a_/h #a_/cb #bhf #adc #fe4j #a_/h #gi4c #ci4g #bc4b #a_/af #aie #ig4f #dd4d #c_/af #fd4c #cb4b #ah4h #a_/h #acc #ff4d #cj4b ----------------------------- ----------------------------- #a_/cb #acg #fh4f #dj4a #a_/fd #ceb #agf #hj4j #c_/af #a_/af #ii4d #di4g #bi4j #c_/af #a_/cb #bdj #abj #ed4e #a_/h #gj4a #ce4j #bj4e #a_/af #afd #hb #cg4c #c_/af #ef4h #bh4d #af4f #a_/h #aab #ef #be4e ----------------------------- ----------------------------- #a_/cb #abf #fb4i #cf4g #a_/fd #cab #aef #gj4i #a_/d #a_/af #ij4h #de4d #bf4e #a_/d #a_/cb #bac #ajg #dh4d #a_/h #fd4a #cb4j #ah4g #a_/af #ade #gb4f #cc4j #c_/af #eb #bf4j #ae4b #c_/cb #aaf #eh4a #bf4d ----------------------------- ----------------------------- #a_/cb #aaa #ee4d #cb4c #a_/fd #bfd #acb #fj4j #c_/h #a_/af #hj #dj4j #bc4d #c_/h #a_/cb #ahj #ij4b #da4j #a_/h #ef4d #bh4b #af4e #a_/af #abb #fa4a #bg4h ----------------------------- ----------------------------- #a_/cb #ajd #eb4a #cj4d #a_/b #a_/fd #bcg #aah #ec4h #a_/b #a_/af #ge4b #cg4f #bb4j #a_/cb #afb #hj4h #cf4g #a_/h #dc4a #ba4f #ab4f ---------------------------------------- ------------------ ,steel--,standard #e_/h-;inch ,tool ,cast ,iron--,standard #e_/h-;inch ,tool ---------------------------------------- ------------------ ,depth,feed ,soft ,medium ,hard ,depth,feed ,soft ,medium ,hard of ,steel ,steel ,steel of ,cast ,cast ,cast ,cut ,cut ,iron ,iron ,iron ---------------------------------------- ------------------ #a_/fd #edh #bgd #abe #a_/cb #afj #hj4j #df4f #a_/af #a_/cb #ceh #agi #ha4f #c_/cb #a_/af #aaj #ee4j #cb4b #a_/af #bce #aag #ec4c #a_/h #ge4d #cg4g #bb4j ---------------------------------------- ------------------ #a_/fd #dfg #bcd #ajf #a_/cb #adh #gd4j #dc4c #c_/cb #a_/cb #cjf #aec #fi4e #a_/h #a_/af #ajd #ea4h #cb4j #a_/af #bjj #ajj #de4e #a_/h #fi4f #cd4h #bj4c #c_/cb #aef #gh #ce4e ----------------------------- ----------------------------- #a_/fd #ahc #ia4f #fh4j #a_/fd #dag #bji #id4h #c_/af #a_/cb #ace #fg4e #ci4d #a_/h #a_/cb #bgc #acf #fb4j #a_/af #id #dg4j #bg4d #a_/af #agi #hi4c #dj4f #a_/h #fd4c #cb4b #ah4h #c_/cb #adj #fi4h #ca4g ----------------------------- ----------------------------- #a_/fd #aga #he4g #ej4a #a_/fd #cfb #aha #hb4b #a_/d #a_/cb #abf #fc4b #cf4i #c_/af #a_/cb #bcf #aah #ec4h #a_/af #hg4h #dc4i #be4f #a_/af #aee #gg4d #ce4b #c_/cb #gj4d #ce4b #bj4f ---------------------------------------- ------------------ #a_/d #a_/fd #cbh #afd #gd4e #c_/h #a_/fd #aef #gg4h #de4d #a_/cb #bae #ajg #dh4h #a_/cb #aaf #eg4h #cc4h ----------------------------- #a_/af #gi4g #ci4i #bc4c #c_/h #a_/fd #bhf #adc #fe4j ---------------------------------------- ------------------ #a ,cutting speeds for tools of a good grade of high-speed steel1 properly ground and heat-treated4--,from ,,machinery',s ,,handbook4 ,average ,cutting ,speeds for ,turning4--,the cutting speed is governed principally by the hardness of the metal to be turned2 the kind of steel of which the turning tool is made2 the shape of the tool and its heat-treatment2 the feed and depth of cut2 whether or not a cooling lubricant is used on the tool2 the power of the lathe and also its construction2 hence it is impossible to give any definite rule for determining either the speed1 feed1 or depth of cut1 because these must be varied to suit existing conditions4 ,a general idea of the speeds used in ordinary machine shop practice may be obtained from the following figures3 ,ordinary machine steel is generally turned at a speed varying between #de and #fe feet per minute4 ,for ordinary gray cast iron1 the speed usually varies from #dj to #ej feet per minute2 for annealed tool steel1 from #be to #ce feet per minute2 for soft yellow brass1 from #aej to #bjj feet per minute2 for hard bronze1 from #ce to #hj feet per minute1 the speed depending upon the composition of the alloy4 ,while these speeds correspond closely to general practice1 they can be exceeded for many machining operations4 ,the most economical speeds for a given feed and depth of cut1 as determined by the experiments conducted by ,mr4 ,f4 ,w4 ,taylor1 are given in the table1 ,cutting ,speeds and ,feeds for ,turning ,tools4 ,the speeds given in this table represent results obtained with tools made of a good grade of high-speed steel properly heat-treated and correctly ground4 ,it will be noted that the cutting speed is much slower for cast iron than for steel4 ,cast iron is cut with less pressure or resistance than soft steel1 but the slower speed required for cast iron is probably due to the fact that the pressure of the chip is concentrated closer to the cutting edge1 combined with the fact that cast iron wears the tool faster than steel4 ,the speeds given are higher than those ordinarily used1 and1 in many cases1 a slower rate would be necessary to prevent chattering or because of some other limiting condition4 ,factors which limit the ,cutting ,speed4--,it is the durability of the turning tool or the length of time that it will turn effectively without grinding1 that limits the cutting speed2 and the hardness of the metal being turned combined with the quality of the tool are the two factors which largely govern the time that a tool can be used before grinding is necessary4 ,the cutting speed for very soft steel or cast iron can be three or four times faster than the speed for hard steel or hard castings1 but whether the material is hard or soft1 the kind and quality of the tool used must also be considered1 as the speed for a tool made of ordinary carbon steel will have to be much slower than for a tool made of modern high-speed steel4 ,when the cutting speed is too high1 even though high-speed steel is used1 the point of the tool is softened to such an extent by the heat resulting from the pressure and friction of the chip1 that the cutting edge is ruined in too short a time4 ,on the other hand1 when the speed is too slow1 the heat generated is so slight as to have little effect and the tool point is dulled by being slowly worn or ground away by the action of the chip4 ,while a tool operating at such a low speed can be used a comparatively long time without re-sharpening1 this advantage is more than offset by the fact that too much time is required for removing a given amount of metal when the work is revolving so slowly4 ,generally speaking1 the speed should be such that a fair amount of work can be done before the tool requires re-grinding4 ,evidently1 it would not pay to grind a tool every few minutes in order to maintain a high cutting speed2 neither would it be economical to use a very slow speed and waste considerable time in turning1 just to save the few minutes required for grinding4 ,for example1 if a number of roughing cuts had to be taken over a heavy rod or shaft1 time might be saved by running at such a speed that the tool would have to be sharpened 7or be replaced by a tool previously sharpened7 when it had traversed half-way across the work2 that is1 the time required for sharpening or changing the tool would be short as compared with the gain effected by the higher work speed4 ,on the other hand1 it might be more economical to run a little slower and take a continuous cut across the work with one tool4 ,the experiments of ,mr4 ,taylor led to the conclusion that1 as a rule1 it is not economical to use roughing tools at a speed so slow as to cause them to last more than #a-a_/b hour without being re-ground2 hence the speeds given in the table previously referred to are based upon this length of time between grindings4 ,sometimes the work speed cannot be as high as the tool will permit1 because of the chattering that often results when the lathe is old and not massive enough to absorb the vibrations1 or when there is unnecessary play in the working parts4 ,the shape of the tool used also affects the work speed1 and as there are so many things to be considered1 the proper cutting speed is best determined by experiment4 ,rules for ,calculating ,cutting ,speeds4--,the number of revolutions required to give any desired cutting speed can be found by multiplying the cutting speed1 in feet per minute1 by #ab and dividing the product by the circumference of the work in inches4 ,expressing this as a formula we have ,c x #ab ,r -------- pid in which ,r revolutions per minute2 ,c the cutting speed in feet per minute2 pi #c4adaf2 d the diameter in inches4 ,for example if a cutting speed of #fj feet per minute is wanted and the diameter of the work is #e inches1 the required speed would be found as follows3 #fj x #ab ,r ---------- #df revolutions per minute4 #c4adaf x #e ,if the diameter is simply multiplied by #c and the fractional part is omitted1 the calculation can easily be made1 and the result will be close enough for practical purposes4 ,in case the cutting speed1 for a given number of revolutions and diameter1 is wanted1 the following formula can be used3 ,rpid ,c ---------- #ab ,machinists who operate lathes do not know1 ordinarily1 what cutting speeds1 in feet per minute1 are used for different classes of work1 but are guided entirely by past experience4 ,feed of ,tool and ,depth of ,cut4--,the amount of feed and depth of cut also vary like the cutting speed1 for different conditions4 ,when turning soft machine steel the feed under ordinary conditions would vary between #a_/cb and #a_/af inch per revolution4 ,for turning soft cast iron the feed might be increased to from #a_/af to #a_/h inch per revolution4 ,these feeds apply to fairly deep roughing cuts4 ,coarser feeds might be used in many cases especially when turning large rigid parts in a powerful lathe4 ,the depth of a roughing cut in machine steel might vary from #a_/h to #c_/h inch1 and in cast iron from #c_/af to #a_/b inch4 ,these figures are intended simply to give the reader a general idea of feeds and cuts that are feasible under average conditions4 ,ordinarily coarser feeds and a greater depth of cut can be used for cast iron than for soft steel1 because cast iron offers less resistance to turning1 but in any case1 with a given depth of cut1 metal can be removed more quickly by using a coarse feed and the necessary slower speed1 than by using a fine feed and the higher speed which is possible when the feed is reduced4 ,when the turning operation is simply to remove metal1 the feed should be coarse1 and the cut as deep as practicable4 ,sometimes the cut must be comparatively light1 either because the work is too fragile and springy to withstand the strain of a heavy cut1 or the lathe has not sufficient pulling power4 ,the difficulty with light slender work is that a heavy cut may cause the part being turned to bend under the strain1 thus causing the tool to gouge in1 which would probably result in spoiling the work4 ,steadyrests can often be used to prevent flexible parts from springing1 as previously explained1 but there are many kinds of light work to which the steadyrest cannot be applied to advantage4 ,the amount of feed to use for a finishing cut might1 properly1 be either fine or coarse4 ,ordinarily1 fine feeds are used for finishing steel1 especially if the work is at all flexible1 whereas finishing cuts in cast iron are often accompanied by a coarse feed4 ,fig4 #ae illustrates the feeds that are often used when turning cast iron4 ,the view to the left shows a deep roughing cut and the one to the right1 a finishing cut4 ,by using a broad flat cutting edge set parallel to the tool's travel1 and a coarse feed for finishing1 a smooth cut can be taken in a comparatively short time4 ,castings which are close to the finished size in the rough can often be finished to advantage by taking a single cut with a broad tool1 provided the work is sufficiently rigid4 ,it is not always practicable to use these broad tools and coarse feeds1 as they sometimes cause chattering1 and when used on steel1 a broad tool tends to gouge or dig in unless the part being turned is rigid4 ,heavy steel parts1 however1 are sometimes finished in this way4 ,the modern method of finishing many steel parts is to simply rough them out in a lathe to within1 say1 #a_/cb inch of the required diameter and take the finishing cut in a cylindrical grinding machine4 ,illustration3 ,fig4 #ae4 ,roughing ,cut--,light ,finishing ,cut and ,coarse ,feed ,effect of ,lubricant on ,cutting ,speed4--,when turning iron or steel a higher cutting speed can be used1 if a stream of soda water or other cooling lubricant falls upon the chip at the point where it is being removed by the tool4 ,in fact1 experiments have shown that the cutting speed1 when using a large stream of cooling water and a high-speed steel tool1 can be about #dj percent higher than when turning dry or without a cooling lubricant4 ,for ordinary carbon steel tools1 the gain was about #be per cent4 ,the most satisfactory results were obtained from a stream falling at a rather slow velocity but in large volume4 ,the gain in cutting speed1 by the use of soda water or other suitable fluids1 was found to be practically the same for all qualities of steel from the softest to the hardest4 ,cast iron is usually turned dry or without a cutting lubricant4 ,experiments1 however1 made to determine the effect of applying a heavy stream of cooling water to a tool turning cast iron1 showed the following results3 ,cutting speed without water1 #dg feet per minute2 cutting speed with a heavy stream of water1 nearly #ed feet per minute2 increase in speed1 #ae per cent4 ,the dirt caused by mixing the fine cast-iron turnings with a cutting lubricant is an objectionable feature which1 in the opinion of many1 more than offsets the increase in cutting speed that might be obtained4 ,turret lathes and automatic turning machines are equipped with a pump and piping for supplying cooling lubricant to the tools in a continuous stream4 ,engine lathes used for general work1 however1 are rarely provided with such equipment and a lubricant1 when used1 is often supplied by a can mounted at the rear of the carriage1 having a spout which extends above the tool4 ,owing to the inconvenience in using a lubricant on an engine lathe1 steel1 as well as cast iron1 is often turned dry especially when the work is small and the cuts light and comparatively short4 ,lubricants ,used for ,turning4--,a good grade of lard oil is an excellent lubricant for use when turning steel or wrought iron and it is extensively used on automatic screw machines1 especially those which operate on comparatively small work4 ,for some classes of work1 especially when high-cutting speeds are used1 lard oil is not as satisfactory as soda water or some of the commercial lubricants1 because the oil is more sluggish and does not penetrate to the cutting point with sufficient rapidity4 ,many lubricants which are cheaper than oil are extensively used on automatics for general machining operations4 ,these usually consist of a mixture of sal-soda 7carbonate of soda7 and water1 to which is added some ingredient such as lard oil or soft soap to thicken or give body to the lubricant4 ,a cheap lubricant for turning1 milling1 etc41 and one that has been extensively used1 is made in the following proportions3 #a pound of sal-soda1 #a quart of lard oil1 #a quart of soft soap1 and enough water to make #aj or #ab gallons4 ,this mixture is boiled for one-half hour1 preferably by passing a steam coil through it4 ,if the solution should have an objectionable odor1 this can be eliminated by adding #b pounds of unslaked lime4 ,the soap and soda in this solution improve the lubricating quality and also prevent the surfaces from rusting4 ,for turning and threading operations1 plain milling1 deep-hole drilling1 etc41 a mixture of equal parts of lard oil and paraffin oil will be found very satisfactory1 the paraffin being added to lessen the expense4 ,brass or bronze is usually machined dry1 although lard oil is sometimes used for automatic screw machine work4 ,babbitt metal is also worked dry1 ordinarily1 although kerosene or turpentine is sometimes used when boring or reaming4 ,if babbitt is bored dry1 balls of metal tend to form on the tool point and score the work4 ,milk is generally considered the best lubricant for machining copper4 ,a mixture of lard oil and turpentine is also used for copper4 ,for aluminum1 the following lubricants can be used3 ,kerosene1 a mixture of kerosene and gasoline1 soap-water1 or aqualine one part1 water #bj parts4 ,lard ,oil as a ,cutting ,lubricant4--,after being used for a considerable time1 lard oil seems to lose some of its good qualities as a cooling compound4 ,there are several reasons for this3 ,some manufacturers use the same oil over and over again on different materials1 such as brass1 steel1 etc4 ,this is objectionable1 for when lard oil has been used on brass it is practically impossible to get the fine dust separated from it in a centrifugal separator4 ,when this impure oil is used on steel1 especially where high-speed steels are employed1 it does not give satisfactory results1 owing to the fact that when the cutting tool becomes dull1 the small brass particles freeze to the cutting tool and thus produce rough work4 ,the best results are obtained from lard oil by keeping it thin1 and by using it on the same materials--that is1 not transferring the oil from a machine in which brass is being cut to one where it would be employed on steel4 ,if the oil is always used on the same class of material1 it will not lose any of its good qualities4 ,prime lard oil is nearly colorless1 having a pale yellow or greenish tinge4 ,the solidifying point and other characteristics of the oil depend upon the temperature at which it was expressed1 winter-pressed lard oil containing less solid constituents of the lard than that expressed in warm weather4 ,the specific gravity should not exceed #j4iaf2 it is sometimes increased by adulterants1 such as cotton-seed and maize oils4 ,,chapter ,,iii ,,taper ,,turning--,,special ,,operations--,,fitting ,it is often necessary1 in connection with lathe work1 to turn parts tapering instead of straight or cylindrical4 ,if the work is mounted between the centers1 one method of turning a taper is to set the tailstock center out of alignment with the headstock center4 ,when both of these centers are in line1 the movement of the tool is parallel to the axis of the work and1 consequently1 a cylindrical surface is produced2 but if the tailstock h#a is set out of alignment1 as shown in ,fig4 #a1 the work will then be turned tapering as the tool is traversed from a to b1 because the axis x--x is at an angle with the movement of the tool4 ,furthermore the amount of taper or the difference between the diameters at the ends for a given length1 will depend on how much center h#a is set over from the central position4 ,illustration3 ,fig4 #a4 ,taper ,turning by the ,offset-center ,method ,illustration3 ,fig4 #b4 ,examples of ,taper ,work ,the amount of taper is usually given on drawings in inches per foot1 or the difference in the diameter at points twelve inches apart4 ,for example1 the taper of the piece shown at ,a1 ,fig4 #b1 is #a inch per foot1 as the length of the tapering surface is just twelve inches and the difference between the diameters at the ends is #a inch4 ,the conical roller shown at ,b has a total length of #i inches and a tapering surface #f inches long1 and in this case the taper per foot is also #a inch1 there being a difference of #a_/b inch in a length of #f inches or #a inch in twice that length4 ,when the taper per foot is known1 the amount that the tailstock center should be set over for turning that taper can easily be estimated1 but it should be remembered that the setting obtained in this way is not absolutely correct1 and is only intended to locate the center approximately4 ,when a taper needs to be at all accurate1 it is tested with a gage1 or by other means1 after taking a trial cut1 as will be explained later1 and the tailstock center is readjusted accordingly4 ,there are also more accurate methods of setting the center1 than by figuring the amount of offset1 but as the latter is often convenient this will be referred to first4 ,setting ,tailstock ,center for ,taper ,turning4--,suppose the tailstock center is to be set for turning part ,c1 ,fig4 #b1 to a taper of approximately #a inch per foot4 ,in this case the center would simply be moved toward the front of the machine #a_/b inch1 or one-half the required taper per foot1 because the total length of the work happens to be just #ab inches4 ,this setting1 however1 would not be correct for all work requiring a taper of #a inch per foot1 as the adjustment depends not only on the amount of the taper but on the total length of the piece4 ,illustration3 ,fig4 #c4 ,detail ,view of ,lathe ,tailstock ,for example1 the taper roller ,b has a taper of #a inch per foot1 but the center1 in this case1 would be offset less than one-half the taper per foot1 because the total length is only #i inches4 ,for lengths longer or shorter than twelve inches1 the taper per inch should be found first2 this is then multiplied by the total length of the work 7not the length of the taper7 which gives the taper for that length1 and one-half this taper is the amount to set over the center4 ,for example1 the taper per inch of part ,b equals #a inch divided by #ab #a_/ab inch4 ,the total length of #i inches multiplied by #a_/ab inch #c_/d inch1 and #a_/b of #c_/d #c_/h1 which is the distance that the tailstock center should be offset4 ,in this example if the taper per foot were not known1 and only the diameters of the large and small ends of the tapered part were given1 the difference between these diameters should first be found 7#b-a_/b-b #a_/b72 this difference should then be divided by the length of the taper 7#a_/b _/ #f #a_/ab inch7 to obtain the taper per inch4 ,the taper per inch times the total length represents what the taper would be if it extended throughout the entire length1 and one-half of this equals the offset1 which is #c_/h inch4 ,example of ,taper ,turning4--,as a practical example of taper turning let us assume that the piece ,a1 ,fig4 #d1 which has been centered and rough-turned as shown1 is to be made into a taper plug1 as indicated at ,b1 to fit a ring gage as at ,c4 ,if the required taper is #a-a_/b inch per foot and the total length is #h inches1 the tailstock center would be offset #a_/b inch4 ,illustration3 ,fig4 #d4 ,taper ,plug and ,gage ,to adjust the tailstock1 the nuts ,n 7,fig4 #c7 are first loosened and then the upper part ,a is shifted sidewise by turning screw ,s4 ,scales are provided on some tailstocks for measuring the amount of this adjustment2 if there is no scale1 draw a line across the movable and stationary parts ,a and ,b1 when the tailstock is set for straight turning4 ,the movement of the upper line in relation to the lower will then show the offset1 which can be measured with a scale4 ,when the adjustment has been made1 nuts ,n are tightened and the part to be turned1 with a dog attached1 is placed between the centers the same as for straight turning4 ,the taper end is then reduced by turning1 but before it is near the finished size1 the work is removed and the taper tested by inserting it in the gage4 ,if it is much out1 this can be felt1 as the end that is too small can be shaken in the hole4 ,suppose the plug did not taper enough and only the small end came into contact with the gage1 as shown somewhat exaggerated at ,d2 in that case the center would be shifted a little more towards the front1 whereas if the taper were too steep1 the adjustment would1 of course1 be in the opposite direction4 ,a light cut would then be taken1 to be followed by another test4 ,if the plug should fit the gage so well that there was no perceptible shake1 it could be tested more closely as follows3 ,draw three or four chalk lines along the tapering surface1 place the work in the gage and turn it a few times4 ,the chalk marks will then show whether the taper of the plug corresponds to that of the gage2 for example1 if the taper is too great1 the marks will be rubbed out on the large end1 but if the taper is correct1 the lines throughout their length will be partially erased4 ,illustration3 ,fig4 #e4 ,setting ,work for ,taper ,turning by use of ,caliper ,gage ,another and more accurate method of testing tapers is to apply a thin coat of ,prussian-blue to one-half of the tapering surface1 in a lengthwise direction4 ,the work is then inserted in the hole or gage and turned to mark the bearing4 ,if the taper is correct1 the bearing marks will be evenly distributed1 whereas if the taper is incorrect1 they will appear at one end4 ,tapering pieces that have to be driven tightly into a hole1 such as a piston-rod1 can be tested by the location of the bearing marks produced by actual contact4 ,after the taper is found to be correct1 the plug is reduced in size until it just enters the gage as at ,c4 ,the final cut should leave it slightly above the required size1 so that a smooth surface can be obtained by filing4 ,it should be mentioned that on work of this kind1 especially if great accuracy is required1 the final finish is often obtained by grinding in a regular grinding machine1 instead of by filing4 ,when this method is employed1 a lathe is used merely to rough-turn the part close to size4 ,illustration3 ,fig4 #f4 ,side ,view showing ,relative ,positions of ,gage and ,work ,when the amount that the tailstock center should be offset is determined by calculating1 as in the foregoing example1 it is usually necessary to make slight changes afterward1 and the work should be tested before it is too near the finished size so that in case one or more trial cuts are necessary1 there will be material enough to permit this4 ,when there are a number of tapered pieces to be turned to the same taper1 the adjustment of the tailstock center will have to be changed unless the total length of each piece and the depth of the center holes are the same in each case4 ,setting the ,tailstock ,center with a ,caliper ,tool4--,another method of setting the tailstock center for taper turning is illustrated in ,fig4 #e4 ,the end of an engine piston-rod is to be made tapering as at ,a and to dimensions a1 b1 c and d4 ,it is first turned with the centers in line as at ,b4 ,the end d is reduced to diameter b up to the beginning of the taper and it is then turned to diameter a as far as the taper part c extends4 ,the tailstock center is next set over by guess and a caliper tool is clamped in the toolpost4 ,this tool1 a side view of which is shown in ,fig4 #f1 has a pointer p that is free to swing about pivot r1 which should be set to about the same height as the center of the work4 ,the tailstock center is adjusted until this pointer just touches the work when in the positions shown by the full and dotted lines at ,c1 ,fig4 #e2 that is1 until the pointer makes contact at the beginning and end of the taper part4 ,the travel of the carriage will then be parallel to a line x--x1 representing the taper2 consequently1 if a tool is started at the small end1 as shown by the dotted lines at ,d1 with the nose just grazing the work1 it will also just graze it when fed to the extreme left as shown4 ,of course1 if the taper were at all steep1 more than one cut would be taken4 ,illustration3 ,fig4 #g4 ,obtaining ,tailstock ,center ,adjustment by use of ,square ,if these various operations are carefully performed1 a fairly accurate taper can be produced4 ,the straight end d is reduced to size after the tail-center is set back to the central position4 ,some mechanics turn notches or grooves at the beginning and end of the tapering part1 having diameters equal to the largest and smallest part of the taper2 the work is then set by these grooves with a caliper tool4 ,the advantage of the first method is that most of the metal is removed while the centers are in alignment4 ,illustration3 ,fig4 #h4 ,second ,step in ,adjusting ,tailstock ,center by use of ,square ,setting the ,tailstock ,center with a ,square4--,still another method of adjusting the tailstock for taper turning1 which is very simple and eliminates all figuring1 is as follows3 ,the part to be made tapering is first turned cylindrical or straight for #c or #d inches of its length1 after the ends have been properly centered and faced square4 ,the work is then removed and the tailstock is shifted along the bed until the distance a--b between the extreme points of the centers is exactly #a foot4 ,the center is next offset a distance b--c equal to one-half the required taper per foot1 after which a parallel strip ,d1 having true sides1 is clamped in the toolpost4 ,part ,d is then set at right angles to a line passing from one center point to the other4 ,this can be done conveniently by holding a #a-;foot square 7preferably with a sliding head7 against one side of ,d and adjusting the latter in the toolpost until edge ,e of the square blade is exactly in line with both center points4 ,after part ,d is set1 it should be clamped carefully to prevent changing the position4 ,the angle between the side of ,d and an imaginary line which is perpendicular to axis a--b is now equal to one-half the angle of the required taper4 ,the axis of the part to be turned should be set parallel with line ,e1 which can be done by setting the cylindrical surface which was previously finished1 at right angles to the side of ,d4 ,in order to do this the work is first placed between centers1 the tailstock being shifted along the bed if necessary2 the tail-center is then adjusted laterally until the finished cylindrical surface is square with the side of ,d4 ,a small try-square can be used for testing the position of the work1 as indicated in ,fig4 #h4 ,if the length of the work is less than #a foot1 it will be necessary to move the center toward the rear of the machine1 and if the length is greater than #a foot1 the adjustment is1 of course1 in the opposite direction4 ,illustration3 ,fig4 #i4 ,a ,lathe ,taper ,attachment ,the ,taper ,attachment4--,turning tapers by setting over the tailstock center has some objectionable features4 ,when the lathe centers are not in alignment1 as when set for taper turning1 they bear unevenly in the work centers because the axis of the work is at an angle with them2 this causes the work centers to wear unevenly and results in inaccuracy4 ,furthermore1 the adjustment of the tailstock center must be changed when turning duplicate tapers1 unless the length of each piece and the depth of the center holes are the same4 ,to overcome these objections1 many modern lathes are equipped with a special device for turning tapers1 known as a taper attachment1 which permits the lathe centers to be kept in alignment1 as for cylindrical turning1 and enables more accurate work to be done4 ,illustration3 ,fig4 #aj4 ,sectional ,view of ,taper ,attachment ,taper attachments1 like lathes1 vary some in their construction1 but all operate on the same principle4 ,an improved form of taper attachment is illustrated in ,figs4 #i and #aj4 ,fig4 #i shows a plan view of a lathe carriage with an attachment fitted to it1 and ,fig4 #aj a sectional view4 ,this attachment has an arm ,a on which is mounted a slide ,s that can be turned about a central pivot by adjusting screw ,d4 ,the arm ,a is supported by1 and is free to slide on1 a bracket ,b 7see also sectional view7 that is fastened to the carriage1 and on one end of the arm there is a clamp ,c that is attached to the lathe bed when turning tapers4 ,on the slide ,s there is a shoe ,f that is connected to bar ,e which passes beneath the toolslide4 ,the rear end of the cross-feed screw is connected to this bar1 and the latter is clamped to the toolslide when the attachment is in use4 ,when a taper is to be turned1 the carriage is moved opposite the taper part and clamp ,c is fastened to the bed2 this holds arm ,a and slide ,s stationary so that the carriage1 with bracket ,b and shoe ,f1 can be moved with relation to the slide4 ,if this slide ,s is set at an angle1 as shown1 the shoe as it moves along causes the toolslide and tool to move in or out1 but if the slide is set parallel to the carriage travel1 the toolslide remains stationary4 ,now if the tool1 as it feeds lengthwise of the work1 is also gradually moved crosswise1 it will turn a taper1 and as this crosswise movement is caused by the angularity of slide ,s1 different tapers are obtained by setting the slide to different positions4 ,by means of a graduated scale ,g at the end of slide ,s1 the taper that will be obtained for any angular position of the slide is shown4 ,on some attachments there are two sets of graduations1 one giving the taper in inches per foot and the other in degrees4 ,while tapers are ordinarily given in inches per foot on drawings1 sometimes the taper is given in degrees instead4 ,the attachment is set for turning tapers by adjusting slide ,s until pointer p is opposite the division or fractional part of a division representing the taper4 ,the whole divisions on the scale represent taper in inches per foot1 and by means of the sub-divisions1 the slide can be set for turning fractional parts of an inch per foot4 ,when slide ,s is properly set1 it is clamped to arm ,a by the nuts ,n4 ,bar ,e is also clamped to the toolslide by bolt ,h1 as previously stated4 ,the attachment is disconnected for straight turning by simply loosening clamp ,c and the bolt ,h4 ,application of ,taper ,attachment4--,practical examples of lathe work1 which illustrate the use of the taper attachment1 are shown in ,figs1 #aa and #ab4 ,fig4 #aa shows how a taper hole is bored in an engine piston-head1 preparatory to reaming4 ,the casting must be held either in a chuck ,c or on a faceplate if too large for the chuck4 ,the side of the casting 7after it has been chucked7 should run true1 and also the circumference1 unless the cored hole for the rod is considerably out of center1 in which case the work should be shifted to divide the error4 ,the side of the casting for a short space around the hole is faced true with a round nose turning tool1 after which the rough-cored hole is bored with an ordinary boring tool t1 and then it is finished with a reamer to exactly the right size and taper4 ,this particular taper attachment is set to whatever taper is given on the drawing1 by loosening nuts ,n and turning slide ,s until pointer ,p is opposite that division on the scale which represents the taper4 ,the attachment is then ready1 after bolt ,h and nuts ,n are tightened1 and clamp ,c is fastened to the lathe bed4 ,the hole is bored just as though it were straight1 and as the carriage advances1 the tool is gradually moved inward by the attachment4 ,if the lathe did not have a taper attachment1 the taper hole could be bored by using the compound rest4 ,illustration3 ,fig4 #aa4 ,lathe with ,taper ,attachment arranged for ,boring ,taper ,hole in ,engine ,piston ,the hole should be bored slightly less than the finish size to allow for reaming4 ,when a reamer is used in the lathe1 the outer end is supported by the tailstock center and should have a deep center-hole4 ,the lathe is run very slowly for reaming and the reamer is fed into the work by feeding out the tailstock spindle4 ,the reamer can be kept from revolving1 either by attaching a heavy dog to the end or1 if the end is squared1 by the use of a wrench long enough to rest against the lathe carriage4 ,a common method is to clamp a dog to the reamer shank1 and then place the tool-rest beneath it to prevent rotation4 ,if the shank of a tool is clamped to the toolpost so that the dog rests against it1 the reamer will be prevented from slipping off the center as it tends to do2 with this arrangement1 the carriage is gradually moved along as the tailstock spindle is fed outward4 ,some reamers are provided with stop-collars which come against the finished side of the casting when the hole has been reamed to size4 ,after the reaming operation1 the casting is removed from the chuck and a taper mandrel is driven into the hole for turning the outside of the piston4 ,this mandrel should run true on its centers1 as otherwise the outside surface of the piston will not be true with the bored hole4 ,the driving dog1 especially for large work of this kind1 should be heavy and stiff1 because light flexible clamps or dogs vibrate and frequently cause chattering4 ,for such heavy work it is also preferable to drive at two points on opposite sides of the faceplate1 but the driving pins should be carefully adjusted to secure a uniform bearing on both sides4 ,the foregoing method of machining a piston is one that would ordinarily be followed when using a standard engine lathe1 and it would1 perhaps1 be as economical as any if only one piston were being made2 but where such work is done in large quantities1 time could be saved by proceeding in a different way4 ,for example1 the boring and reaming operation could be performed much faster in a turret lathe1 which is a type designed for just such work1 but a turret lathe cannot be used for as great a variety of turning operations as a lathe of the regular type4 ,there are also many other classes of work that can be turned more quickly in special types of machines1 but as more or less time is required for arranging these special machines and often special tools have to be made1 the ordinary lathe is frequently indispensable when only a few parts are needed2 in addition1 it is better adapted to some turning operations than any other machine4 ,fig4 #ab illustrates how a taper attachment would be used for turning the taper fitting for the crosshead end of an engine piston-rod4 ,even though this taper corresponds to the taper of the hole in the piston1 slide ,s would have to be reset to the corresponding division on the opposite side of the central zero mark1 because the taper of the hole decreased in size during the boring operation1 whereas the rod is smallest at the beginning of the cut1 so that the tool must move outward rather than inward as it advances4 ,the taper part is turned practically the same as a cylindrical part2 that is1 the power feed is used and1 as the carriage moves along the bed1 the tool is gradually moved outward by the taper attachment4 ,illustration3 ,fig4 #ab4 ,taper ,attachment ,set for ,turning ,taper ,end of ,piston-rod ,if the rod is being fitted directly to the crosshead 7as is usually the case71 the approximate size of the small end of the taper could be determined by calipering1 the calipers being set to the size of the hole at a distance from the shoulder or face side of the crosshead1 equal to the length of the taper fitting on the rod4 ,if the crosshead were bored originally to fit a standard plug gage1 the taper on the rod could be turned with reference to this gage1 but1 whatever the method1 the taper should be tested before turning too close to the finished size4 ,the test is made by removing the rod from the lathe and driving it tightly into the crosshead4 ,this shows how near the taper is to size1 and when the rod is driven out1 the bearing marks show whether the taper is exactly right or not4 ,if the rod could be driven in until the shoulder is1 say1 #a_/h inch from the crosshead face1 it would then be near enough to finish to size by filing4 ,when filing1 the lathe is run much faster than for turning1 and most of the filing should be done where the bearing marks are the heaviest1 to distribute the bearing throughout the length of the taper4 ,care should be taken when driving the rod in or out1 to protect the center-holes in the ends by using a soft hammer or holding a piece of soft metal against the driving end4 ,illustration3 ,fig4 #ac4 ,tool ,point should be in same ,horizontal ,plane as ,axis of ,work for ,taper ,turning ,after the crosshead end is finished1 the rod is reversed in the lathe for turning the piston end4 ,the dog is clamped to the finished end1 preferably over a piece of sheet copper to prevent the surface from being marred4 ,when turning this end1 either the piston reamer or the finished hole in the piston can be calipered4 ,the size and angle of the taper are tested by driving the rod into the piston1 and the end should be fitted so that by driving tightly1 the shoulder will just come up against the finished face of the piston4 ,when the taper is finished1 the attachment is disengaged and a finishing cut is taken over the body of the rod1 unless it is to be finished by grinding1 which is the modern and most economical method4 ,height of ,tool when ,turning ,tapers4--,the cutting edge of the tool1 when turning tapers1 should be at the same height as the center or axis of the work1 whether an attachment is used or not4 ,the importance of this will be apparent by referring to ,fig4 #ac4 ,to turn the taper shown1 the tool ,t would be moved back a distance x 7assuming that an attachment is used7 while traversing the length l4 ,as an illustration1 if the tool could be placed as high as point a1 the setting of the attachment remaining as before1 the tool would again move back a distance x1 while traversing a distance l1 but the large end would be under-sized 7as shown by the dotted line7 if the diameters of the small ends were the same in each case4 ,of course1 if the tool point were only slightly above or below the center1 the resulting error would also be small4 ,the tool can easily be set central by comparing the height of the cutting edge at the point of the tool with one of the lathe centers before placing the work in the lathe4 ,illustration3 ,fig4 #ad4 ,plan ,view showing ,method of ,turning a ,taper with the ,compound ,rest ,taper ,turning with the ,compound ,rest4--,the amount of taper that can be turned by setting over the tailstock center and by the taper attachment is limited1 as the centers can only be offset a certain distance1 and the slide ,s 7,fig4 #i7 of the attachment cannot be swiveled beyond a certain position4 ,for steep tapers1 the compound rest ,e is swiveled to the required angle and used as indicated in ,fig4 #ad1 which shows a plan view of a rest set for turning the valve ,v4 ,this compound rest is an upper slide mounted on the lower or main cross-slide ,d1 and it can be turned to any angular position so that the tool1 which ordinarily is moved either lengthwise or crosswise of the bed1 can be fed at an angle4 ,the base of the compound rest is graduated in degrees and the position of these graduations shows to what angle the upper slide is set4 ,suppose the seat of valve ,v is to be turned to an angle of #de degrees with the axis or center1 as shown on the drawing at ,a1 ,fig4 #ae4 ,to set the compound rest1 nuts n on either side1 which hold it rigidly to the lower slide1 are first loosened and the slide is then turned until the #de-;degree graduation is exactly opposite the zero line2 the slide is then tightened in this position4 ,a cut is next taken across the valve by operating handle w and feeding the tool in the direction of the arrow4 ,illustration3 ,fig4 #ae4 ,example of ,taper ,work ,turned by using ,compound ,rest ,in this particular instance the compound rest is set to the same angle given on the drawing1 but this is not always the case4 ,if the draftsman had given the included angle of #ij degrees1 as shown at ,b1 which would be another way of expressing it1 the setting of the compound rest would1 of course1 be the same as before1 or to #de degrees1 but the number of degrees marked on the drawing does not correspond with the angle to which the rest must be set4 ,as another illustration1 suppose the valve were to be turned to an angle of #cj degrees with the axis as shown at ,c4 ,in this case the compound rest would not be set to #cj degrees but to #fj degrees1 because in order to turn the work to an angle of #cj degrees1 the rest must be #fj degrees from its zero position1 as shown4 ,from this it will be seen that the number of degrees marked on the drawing does not necessarily correspond to the angle to which the rest must be set1 as the graduations on the rest show the number of degrees that it is moved from its zero position1 which corresponds to the line a--b4 ,the angle to which the compound rest should be set can be found1 when the drawing is marked as at ,a or ,c1 by subtracting the angle given from #ij degrees4 ,when the included angle is given1 as at ,b1 subtract one-half the included angle from #ij degrees to obtain the required setting4 ,of course1 when using a compound rest1 the lathe centers are set in line as for straight turning1 as otherwise the angle will be incorrect4 ,rules for ,figuring ,tapers ---------------------------------------- ---------------------------- ,given ,to ,find ,rule ---------------------------------------- ---------------------------- ,the taper per foot4 ,the taper per inch4 ,divide the taper per foot by #ab4 ,the taper per inch4 ,the taper per foot4 ,multiply the taper per inch by #ab4 ,end diameters and ,the taper per foot4 ,subtract small diameter length of taper in from large2 divide by inches4 length of taper1 and multiply quotient by #ab4 ,large diameter and ,diameter at small ,divide taper per foot by length of taper in end in inches4 #ab2 multiply by length inches and taper of length of taper1 and per foot4 subtract result from large diameter4 ,small diameter and ,diameter at large ,divide taper per foot by length of taper in end in inches4 #ab2 multiply by length inches1 and taper of taper1 and add result per foot4 to small diameter4 ,the taper per foot ,distance between ,subtract small diameter and two diameters two given diameters from large2 divide re- in inches4 in inches4 mainder by taper per foot1 and multiply quotient by #ab4 ,the taper per foot4 ,amount of taper in ,divide taper per foot by a certain length #ab2 multiply by given given in inches4 length of tapered part4 ---------------------------------------- ---------------------------- ,accurate ,measurement of ,angles and ,tapers4--,when great accuracy is required in the measurement of angles1 or when originating tapers1 disks are commonly used4 ,the principle of the disk method of taper measurement is that if two disks of unequal diameters are placed either in contact or a certain distance apart1 lines tangent to their peripheries will represent an angle or taper1 the degree of which depends upon the diameters of the two disks and the distance between them4 ,the gage shown in ,fig4 #af1 which is a form commonly used for originating tapers or measuring angles accurately1 is set by means of disks4 ,this gage consists of two adjustable straight-edges ,a and ,a#a1 which are in contact with disks ,b and ,b#a4 ,the angle alpha or the taper between the straight-edges depends1 of course1 upon the diameters of the disks and the center distance ,c1 and as these three dimensions can be measured accurately1 it is possible to set the gage to a given angle within very close limits4 ,moreover1 if a record of the three dimensions is kept1 the exact setting of the gage can be reproduced quickly at any time4 ,the following rules may be used for adjusting a gage of this type4 ,illustration3 ,fig4 #af4 ,disk ,gage for ,accurate ,measurement of ,angles and ,tapers ,to ,find ,center ,distance for a ,given ,taper4--,when the taper1 in inches per foot1 is given1 to determine center distance ,c4 ,rule3 ,divide the taper by #bd and find the angle corresponding to the quotient in a table of tangents2 then find the sine corresponding to this angle and divide the difference between the disk diameters by twice the sine4 ,example3 ,gage is to be set to #c_/d inch per foot1 and disk diameters are #a4be and #a4e inch1 respectively4 ,find the required center distance for the disks4 #j4ge ---- #j4jcabe4 #bd ,the angle whose tangent is #j4jcabe equals #a degree #dg4d minutes2 sin #a deg4 #dg4d' #j4jcabc2 #a4ej - #a4be #j4be inch2 #j4be ----------- #d4jjb inches center distance ,c4 #b x #j4jcabc ,to ,find ,center ,distance for a ,given ,angle4--,when straight-edges must be set to a given angle alpha1 to determine center distance ,c between disks of known diameter4 ,rule3 ,find the sine of half the angle alpha in a table of sines2 divide the difference between the disk diameters by double this sine4 ,example3 ,if an angle alpha of #bj degrees is required1 and the disks are #a and #c inches in diameter1 respectively1 find the required center distance ,c4 #bj ---- #aj degrees2 sin #aj deg4 #j4agcfe2 #b #c - #a ----------- #e4gei inches center distance ,c4 #b x #j4agcfe ,to ,find ,angle for ,given ,taper per ,foot4--,when the taper in inches per foot is known1 and the corresponding angle alpha is required4 ,rule3 ,divide the taper in inches per foot by #bd2 find the angle corresponding to the quotient1 in a table of tangents1 and double this angle4 ,example3 ,what angle alpha is equivalent to a taper of #a-a_/b inch per foot8 #a4e --- #j4jfbe4 #bd ,the angle whose tangent is #j4jfbe equals #c degrees #ce minutes1 nearly2 then1 #c deg4 #ce min4 x #b #g deg4 #aj min4 ,to ,find ,angle for ,given ,disk ,dimensions4--,when the diameters of the large and small disks and the center distance are given1 to determine the angle alpha4 ,rule3 ,divide the difference between the disk diameters by twice the center distance2 find the angle corresponding to the quotient1 in a table of sines1 and double the angle4 ,example3 ,if the disk diameters are #a and #a4e inch1 respectively1 and the center distance is #e inches1 find the included angle alpha4 #a4e - #a ------- #j4je4 #b x #e ,the angle whose sine is #j4je equals #b degrees #eb minutes2 then1 #b deg4 #eb min4 x #b #e deg4 #dd min4 angle alpha4 ,illustration3 ,fig4 #ag4 ,setting ,center ,mark in ,line with ,axis of ,lathe ,spindle by use of ,test ,indicator ,illustration3 ,fig4 #ah4 ,jig-plate with ,buttons attached1 ready for ,boring ,use of the ,center ,indicator4--,the center test indicator is used for setting a center-punch mark1 the position of which corresponds with the center or axis of the hole to be bored1 in alignment with the axis of the lathe spindle4 ,to illustrate1 if two holes are to be bored1 say #e inches apart1 small punch marks having that center-to-center distance would be laid out as accurately as possible4 ,one of these marks would then be set central with the lathe spindle by using a center test indicator as shown in ,fig4 #ag4 ,this indicator has a pointer ,a the end of which is conical and enters the punch mark4 ,the pointer is held by shank ,b which is fastened in the toolpost4 ,the joint ,c by means of which the pointer is held to the shank is universal2 that is1 it allows the pointer to move in any direction4 ,now when the part being tested is rotated by running the lathe1 if the center-punch mark is not in line with the axes of the lathe spindle1 obviously the outer end of pointer ,a will vibrate1 and as joint ,c is quite close to the inner end1 a very slight error in the location of the center-punch mark will cause a perceptible movement of the outer end1 as indicated by the dotted lines4 ,when the work has been adjusted until the pointer remains practically stationary1 the punch mark is central1 and the hole is bored4 ,the other center-punch mark is then set in the same way for boring the second hole4 ,the accuracy of this method depends1 of course1 upon the location of the center-punch marks4 ,a still more accurate way of setting parts for boring holes to a given center-to-center distance is described in the following3 ,locating ,work by the ,button ,method4--,among the different methods employed by machinists and toolmakers for accurately locating work such as jigs1 etc41 on the faceplate of a lathe1 the one most commonly used is known as the button method4 ,this scheme is so named because cylindrical bushings or buttons are attached to the work in positions corresponding to the holes to be bored1 after which they are used in locating the work4 ,these buttons1 which are ordinarily about #a_/b inch in diameter1 are ground and lapped to the same size and the ends squared4 ,the diameter should1 preferably1 be such that the radius can be determined easily1 and the hole through the center should be about #a_/h inch larger than the retaining screw1 so that the button can be shifted4 ,as an illustration of the practical application of the button method1 we shall consider1 briefly1 the way the holes would be accurately machined in the jig-plate in ,fig4 #ah4 ,first the centers of the seven holes should be laid off approximately correct by the usual methods1 after which small holes should be drilled and tapped for the clamping screws ,s4 ,after the buttons ,b are clamped lightly in place1 they are all set in correct relation with each other and with the jig-plate4 ,the proper location of the buttons is very important as their positions largely determine the accuracy of the work4 ,a definite method of procedure that would be applicable in all cases cannot1 of course1 be given1 as the nature of the work as well as the tools available make it necessary to employ different methods4 ,illustration3 ,fig4 #ai4 ,setting a ,button ,true ,preparatory to ,boring1 by use of ,test ,indicator ,in this particular case1 the three buttons a1 b and c should be set first1 beginning with the one in the center4 ,as this central hole must be #b4cj and #b4fe inches from the finished sides ,a and ,a#a1 respectively1 the work is first placed on an accurate surface-plate as shown2 by resting it first on one of these sides and then on the other1 and measuring with a vernier height gage1 the central button can be accurately set4 ,the buttons a and c are also set to the correct height from side ,a#a by using the height gage1 and in proper relation to the central button by using a micrometer or a vernier caliper and measuring the over-all dimension x4 ,when measuring in this way1 the diameter of one button would be deducted to obtain the correct center-to-center distance4 ,after buttons a1 b and c are set equidistant from side ,a#a and in proper relation to each other1 the remaining buttons should be set radially from the central button b and the right distance apart4 ,by having two micrometers or gages1 one set for the radial dimension x and the other for the chordal distance y1 the work may be done in a comparatively short time4 ,illustration3 ,fig4 #bj4 ,testing ,concentricity of ,button with ,dial ,gage ,after the buttons have been tightened1 all measurements should be carefully checked2 the work is then mounted on the faceplate of the lathe1 and one of the buttons1 say b1 is set true by the use of a test indicator as shown in ,fig4 #ai4 ,when the end of this indicator 7which is one of a number of types on the market7 is brought into contact with the revolving button1 the vibration of the pointer ,i shows how much the button runs out of true4 ,when the pointer remains practically stationary1 thus showing that the button runs true1 the latter should be removed4 ,the hole is then drilled nearly to the required size1 after which it is bored to the finish diameter4 ,in a similar manner the other buttons are indicated and the holes bored1 one at a time4 ,it is evident that if each button is correctly located and set perfectly true in the lathe1 the various holes will be located at the required center-to-center dimensions within very close limits4 ,illustration3 ,fig4 #ba4 ,drilling a ,bushing ,hole ,fig4 #bj shows how one of the buttons attached to a plate in which three holes are to be bored is set true or concentric4 ,the particular indicator illustrated is of the dial type1 any error in the location of the button being shown by a hand over a dial having graduations representing thousandths of an inch4 ,fig4 #ba shows how the hole is drilled after the button is removed4 ,it will be noted that the drill is held in a chuck1 the taper shank of which fits into the tailstock spindle1 this being the method of holding small drills4 ,after drilling1 the hole is bored as shown in ,fig4 #bb4 ,the boring tool should have a keen edge to avoid springing1 and if the work when clamped in position1 throws the faceplate out of balance1 it is advisable to restore the balance1 before boring1 by the use of a counter-weight1 because the lathe can be rotated quite rapidly when boring such a small hole4 ,illustration3 ,fig4 #bb4 ,boring a ,bushing ,hole ,when doing precision work of this kind1 the degree of accuracy will depend upon the instruments used1 the judgment and skill of the workman and the care exercised4 ,a good general rule to follow when locating bushings or buttons is to use the method which is the most direct and which requires the least number of measurements4 ,as an illustration of how errors may accumulate1 let us assume that seven holes are to be bored in the jig-plate shown in ,fig4 #bc1 so that they are the same distance from each other and in a straight line4 ,the buttons may be brought into alignment by the use of a straight-edge1 and to simplify matters1 it will be taken for granted that they have been ground and lapped to the same size4 ,if the diameter of the buttons is first determined by measuring with a micrometer1 and then this diameter is deducted from the center distance x1 the difference will be the distance y between adjacent buttons4 ,now if a temporary gage is made to length y1 all the buttons can be set practically the same distance apart1 the error between any two adjacent ones being very slight4 ,if1 however1 the total length z over the end buttons is measured by some accurate means1 the chances are that this distance will not equal six times dimension x plus the diameter of one button1 as it should1 because even a very slight error in the gage for distance y would gradually accumulate as each button was set4 ,if a micrometer were available that would span two of the buttons1 the measurements could be taken direct and greater accuracy would doubtless be obtained4 ,on work of this kind where there are a number of holes that need to have accurate over-all dimensions1 the long measurements should first be taken when setting the buttons1 providing1 of course1 there are proper facilities for so doing1 and then the short ones4 ,for example1 the end buttons in this case should first be set1 then the central one and finally those for the sub-divisions4 ,illustration3 ,fig4 #bc4 ,example of ,work illustrating ,accumulation of ,errors ,eccentric ,turning4--,when one cylindrical surface must be turned eccentric to another1 as when turning the eccentric of a steam engine1 an arbor having two sets of centers is commonly used1 as shown in ,fig4 #bd4 ,the distance x between the centers must equal one-half the total throw or stroke of the eccentric4 ,the hub of the eccentric is turned upon the centers a--a1 and the tongued eccentric surface1 upon the offset centers1 as indicated by the illustration4 ,sometimes eccentrics are turned while held upon special fixtures attached to the faceplate4 ,illustration3 ,fig4 #bd4 ,special ,arbor for ,turning ,eccentrics ,when making an eccentric arbor1 the offset center in each end should be laid out upon radial lines which can be drawn across the arbor ends by means of a surface gage4 ,each center is then drilled and reamed to the same radius x as near as possible4 ,the uniformity of the distance x at each end is then tested by placing the mandrel upon the offset centers and rotating it1 by hand1 with a dial indicator in contact at first one end and then the other4 ,the amount of offset can also be tested either by measuring from the point of a tool held in the toolpost1 or by setting the tool to just graze the mandrel at extreme inner and outer positions1 and noting the movement of the cross-slide by referring to the dial gage of the cross-feed screw4 ,illustration3 ,fig4 #be4 ,turning an ,engine ,crank-pin in an ,ordinary ,lathe ,turning a ,crankshaft in a ,lathe4--,another example of eccentric turning is shown in ,fig4 #be4 ,the operation is that of turning the crank-pin of an engine crankshaft1 in an ordinary lathe4 ,the main shaft is first rough-turned while the forging revolves upon its centers ,c and ,c#a and the ends are turned to fit closely the center-arms ,a and ,a#a4 ,after the sides ,b and ,b#a of the crank webs have been rough-faced1 the center-arms are attached to the ends of the shaft as shown in the illustration4 ,these arms have centers at ,d and ,d#a 7located at the required crank radius7 which should be aligned with the rough pin1 when attaching the arms1 and it is advisable to insert braces ,e between the arms and crank to take the thrust of the lathe centers4 ,with the forging supported in this way1 the crank-pin and inner sides of the webs are turned and faced1 the work revolving about the axis of the pin4 ,the turning tools must extend beyond the tool-holder far enough to allow the crank to clear as it swings around4 ,owing to this overhang1 the tool should be as heavy as possible to make it rigid and it is necessary to take comparatively light cuts and proceed rather cautiously4 ,after finishing the crank-pin and inside of the crank1 the center-arms are removed and the main body of the shaft and the sides ,b and ,b#a are finished4 ,this method of turning crankshafts is often used in general repair shops1 etc41 especially where new shafts do not have to be turned very often4 ,it is slow and inefficient1 however1 and where crankshafts are frequently turned1 special machines or attachments are used4 ,illustration3 ,fig4 #bf4 ,le,blond ,lathe with ,special ,equipment for ,crankshaft ,turning ,special ,crankshaft ,lathe4--,a lathe having special equipment for rough-turning gas engine crankshaft pins is shown in ,fig4 #bf4 ,this lathe is a heavy-duty type built by the ,r4 ,k4 ,le,blond ,machine ,tool ,co4 ,it is equipped with special adjustable headstock and tailstock fixtures designed to take crankshafts having strokes up to about #f inches4 ,the tools are held in a three-tool turret type of toolpost and there are individual cross-stops for each tool4 ,this lathe also has a roller steadyrest for supporting the crankshaft2 automatic stops for the longitudinal feed1 and a pump for supplying cutting lubricant4 ,the headstock fixture is carried on a faceplate mounted on the spindle and so arranged as to be adjustable for cranks of different throw4 ,when the proper adjustment for a given throw has been made1 the slide is secured by four ,t-bolts4 ,a graduated scale and adjusting screw permit of accurate adjustments4 ,the revolving fixture is accurately indexed for locating different crank-pins in line with the lathe centers1 by a hardened steel plunger in the slide which engages with hardened bushings in the fixture4 ,the index is so divided that the fixture may be rotated #abj or #ahj degrees1 making it adjustable for #b-1 #d- and #f-throw cranks4 ,after indexing1 the fixture is clamped by two ,t-bolts which engage a circular ,t-slot4 ,the revolving fixture is equipped with removable split bushings which can be replaced to fit the line bearings of different sized crankshafts4 ,the work is driven by a ,v-shaped dovetail piece having a hand-nut adjustment1 which also centers the pin by the cheek or web4 ,the crank is held in position by a hinged clamp on the fixture4 ,the tailstock fixture is also adjustable and it is mounted on a spindle which revolves in a bushing in the tailstock barrel4 ,the adjustment is obtained in the same manner as on the headstock fixture1 and removable split bushings as well as a hinged clamp are also employed4 ,the method of chucking a four-throw crank is as follows3 ,the two fixtures are brought into alignment by two locking pins4 ,one of these is located in the head and enters a bushing in the large faceplate and the other is in the tailstock and engages the tailstock fixture4 ,the crankshaft is delivered to the machine with the line bearings rough-turned and it is clamped by the hinged clamp previously referred to and centered by the ,v-shaped driver4 ,the locking pins for both fixtures are then withdrawn and the machine is ready to turn two of the pins4 ,after these have been machined1 the fixtures are again aligned by the locking pins1 the two ,t-bolts of the headstock fixture and the hinged clamp at the tailstock are released1 the indexing plunger is withdrawn and the headstock fixture and crank are turned #ahj degrees or until the index plunger drops into place4 ,the crank is then clamped at the tailstock end and the revolving fixture is secured by the two ,t-bolts previously referred to4 ,after the locking pins are withdrawn1 the lathe is ready to turn the two opposite pins4 ,illustration3 ,fig4 #bg4 ,diagrams showing ,arrangements of ,tools on ,le,blond ,lathe ,operation of ,special ,crankshaft ,lathe4--,the total equipment of this machine 7see ,fig4 #bg7 is carried on a three-tool turret tool-block4 ,the method of turning a crankshaft is as follows3 ,a round-nosed turning tool is first fed into a cross stop as illustrated in the plan view at ,a1 which gives the proper diameter4 ,the feed is then engaged and the tool feeds across the pin until the automatic stop lever engages the first stop1 which throws out the feed automatically4 ,the carriage is then moved against a positive stop by means of the handwheel4 ,the roller back-rest is next adjusted against the work by the cross-feed handwheel operating through a telescopic screw1 and the filleting tools are brought into position as at ,b4 ,these are run in against a stop1 removing the part left by the turning tool and giving the pin the proper width and fillets of the correct radius4 ,if the crankshaft has straight webs which must be finished1 two tools seen at b are used for facing the webs to the correct width4 ,during these last two operations1 the crank is supported by the roller back-rest1 thus eliminating any tendency of the work to spring4 ,illustration3 ,fig4 #bh4 7,a7 ,spherical ,turning with ,compound ,rest4 7,b7 ,concave ,turning ,after one pin is finished in the manner described1 the back-rest is moved out of the way1 the automatic stop lever raised1 the carriage shifted to the next pin1 and the operation repeated4 ,the tools are held in position on the turret by studs1 and they can be moved and other tools quickly substituted for pins of different widths4 ,this machine is used for rough-turning the pins close to the required size1 the finishing operation being done in a grinder4 ,it should be mentioned1 in passing1 that many crankshafts1 especially the lighter designs used in agricultural machinery1 etc41 are not turned at all but are ground from the rough4 ,spherical ,turning4--,occasionally it may be necessary to turn a spherical surface in the lathe4 ,sketch ,a1 ,fig4 #bh1 shows how a small ball-shaped end can be turned on a piece held in a chuck4 ,the lathe carriage is adjusted so that the pin around which the compound rest swivels is directly under the center a4 ,the bolts which hold the swivel are slightly loosened to allow the top slide to be turned1 as indicated by the dotted lines2 this causes the tool point to move in an arc about center a1 and a spherical surface is turned4 ,light cuts must be taken as otherwise it would be difficult to turn the slide around by hand4 ,illustration3 ,fig4 #bi4 ,spherical ,turning ,attachment for ,engine ,lathe ,sketch ,b illustrates how a concave surface can be turned4 ,the cross-slide is adjusted until swivel pin is in line with the lathe centers1 and the carriage is moved along the bed until the horizontal distance between center b of the swivel1 and the face of the work1 equals the desired radius of the concave surface4 ,the turning is then done by swinging the compound rest as indicated by the dotted lines4 ,the slide can be turned more evenly by using the tailstock center to force it around4 ,a projecting bar is clamped across the end of the slide at d1 to act as a lever1 and a centered bar is placed between this lever and the tailstock center2 then by screwing out the tailstock spindle1 the slide is turned about pivot b4 ,the alignment between the swivel pin and the lathe centers can be tested by taking a trial cut2 if the swivel pin is too far forward1 the tool will not touch the turned surface if moved past center c1 and if the pin is too far back1 the tool will cut in on the rear side4 ,spherical ,turning ,attachments4--,when spherical turning must be done repeatedly1 special attachments are sometimes used4 ,fig4 #bi shows an attachment applied to a lathe for turning the spherical ends of ball-and-socket joints4 ,the height or radius of the cutting tool and1 consequently1 the diameter of the turned ball1 is regulated by adjusting screw ,a4 ,the tool is swung around in an arc1 by turning handle ,b which revolves a worm meshing with an enclosed worm-wheel4 ,as will be seen1 the work is held in a special chuck1 owing to its irregular shape4 ,illustration3 ,fig4 #cj4 ,attachment for ,turning ,spherical ,end of ,gasoline ,engine ,piston ,another spherical turning attachment is shown in ,fig4 #cj4 ,this is used for machining the ends of gasoline engine pistons4 ,the cross-slide has bolted to it a bar ,a carrying a roller which is pressed against a forming plate ,b by a heavy spring ,c4 ,the forming plate ,b1 which is attached to a cross-piece fastened to the ways of the lathe bed1 is curved to correspond with the radius required on the piston end1 and when the tool is fed laterally by moving the cross-slide1 it follows the curve of plate ,b4 ,the piston is held in a special hollow chuck which locates it in a central position and holds it rigidly4 ,in connection with lathe work1 special attachments and tools are often used1 especially when considerable work of one class must be turned2 however1 if a certain part is required in large quantities1 it is usually more economical to use some semi-automatic or automatic turning machine1 especially designed for repetition work4 ,turning with ,front and ,rear ,tools4--,in ordinary engine lathe practice1 one tool is used at a time1 but some lathes are equipped with tool-holders at the front and rear of the carriage so that two tools can be used simultaneously4 ,fig4 #ca shows a detail view of a lathe in which front and rear tools are being used4 ,these tools are of the inserted cutter type and the one at the rear is inverted1 as the rotary movement of the work is1 of course1 upward on the rear side4 ,this particular lathe was designed for taking heavy roughing cuts and has considerable driving power4 ,illustration3 ,fig4 #ca4 ,front and ,rear ,tools used for ,roughing ,the part shown in this illustration is a chrome-nickel steel bar which is being roughed out to form a milling machine spindle4 ,it is necessary to reduce the diameter of the bar from #e-g_/af inches to #c-c_/d inches for a length of #bg inches1 because of a collar on one end4 ,this reduction is made in one passage of the two tools1 with a feed of #a_/cb inch per revolution and a speed of #fj revolutions per minute4 ,the use of two tools for such heavy roughing cuts is desirable1 especially when the parts are required in large quantities1 because the thrust of the cut on one side1 which tends to deflect the work1 is counteracted by the thrust on the opposite side4 ,illustration3 ,fig4 #cb4 ,lo-swing ,lathe for ,multiple ,turning ,sometimes special tool-holders are made for the lathe1 so that more than one tool can be used for turning different surfaces or diameters at the same time1 the tools being set in the proper relation to each other4 ,the advantage of this method has resulted in the design of a special lathe for multiple-tool turning4 ,a ,multiple-tool ,lathe4--,the lathe shown in ,fig4 #cb 7which is built by the ,fitchburg ,machine ,works and is known as the ,lo-swing7 is designed especially for turning shafts1 pins and forgings not exceeding #c-a_/b inches in diameter4 ,it has two carriages ,a and ,b which1 in conjunction with special tool-holders1 make it possible to turn several different diameters simultaneously4 ,at the front of this lathe there is an automatic stop-rod ,c for disengaging the feed when the tools have turned a surface to the required length4 ,this stop-rod carries adjustable stops ,d which are set to correspond with shoulders1 etc41 on the work4 ,the rod itself is also adjustable axially1 so that the tools1 which are usually arranged in groups of two or more 7depending upon the nature of the work71 can be disengaged at a point nearer or farther from the headstock as may be required1 owing to a variation in the depth of center holes4 ,for example1 if it were necessary to feed a group of tools farther toward the headstock after they had been automatically disengaged1 the entire rod with its stops would be adjusted the required amount in that direction4 ,illustration3 ,fig4 #cc4 ,lo-swing ,lathe arranged for ,turning a ,steering ,knuckle ,the gage ,g1 which is attached to a swinging arm1 is used to set the stop bar with reference to a shoulder near the end of the work1 when it is necessary to finish other parts to a given distance from such a shoulder or other surface4 ,the use of this gage will be explained more fully later4 ,cooling lubricant for the tools is supplied through the tubes ,e4 ,the lathe shown in the illustration is arranged for turning ,krupp steel bars4 ,a rough bar and also one that has been turned may be seen to the right4 ,the plain cylindrical bar is turned to five different diameters1 by groups of tools held on both carriages4 ,illustration3 ,fig4 #cd4 ,plan ,view showing ,method of driving ,steering ,knuckle and ,arrangement of ,tools ,examples of ,multiple ,turning4--,figs4 #cc and #cd show how a ,lo-swing lathe is used for turning the steering knuckle of an automobile4 ,four tools are used in this case1 three cylindrical surfaces and one tapering surface being turned at the same time4 ,for this job1 the four tools are mounted on one carriage4 ,the taper part is turned by the second tool from the headstock1 which is caused to feed outward as the carriage advances by a taper attachment4 ,this tool is held in a special holder and bears against a templet at the rear1 which is tapered to correspond with the taper to be turned4 ,this templet is attached to a bar which1 in turn1 is fastened to a stationary bracket seen to the extreme left in ,fig4 #cc4 ,this part is finished in two operations1 the tool setting being identical for each operation1 except for diameter adjustments4 ,as the illustrations show1 three of the four tools employed are used for straight turning on different diameters1 while the fourth finishes the taper4 ,these pieces1 which are rough drop forgings1 are first reduced to the approximate size4 ,when it becomes necessary to grind the tools1 they are reset and those parts which have been roughed out are turned to the finished size4 ,the average time for the first operation1 which includes starting1 stopping1 turning and replacing the piece1 is one minute1 while for the second operation with the finer feed1 an average time of two minutes is required4 ,the work is driven by sleeve ,s1 which fits over the spindle and is held in position by the regular driver1 as shown4 ,this sleeve is notched to fit the knuckle1 so that the latter can easily and quickly be replaced when finished4 ,one of the interesting features of this job lies in the method of locating the shoulders on each knuckle1 at the same distance from the hole ,h which is drilled previously1 and which receives the bolt on which the knuckle swivels when assembled in a car4 ,as soon as the knuckle has been placed between the centers1 a close-fitting plug ,p 7,fig4 #cc7 is inserted in this hole and the indicator arm with its attached gage or caliper ,g is swung up to the position shown4 ,the stop-rod on which the stops have been previously set for the correct distance between the shoulders is next adjusted axially until the gage ,g just touches the plug ,p4 ,the indicator is then swung out of the way1 and the piece turned4 ,if the next knuckle were centered1 say1 deeper than the previous one which would1 of course1 cause it to be located nearer the headstock1 obviously all the shoulders would be located farther from the finished hole1 provided the position of the stops remained the same as before4 ,in such a case their position would1 however1 be changed by shifting the stop-rod until the gage ,g again touched the plug thus locating all the stops with reference to the hole4 ,as the adjustment of the stop-rod changes the position of the taper templet as well as the stops1 it is evident that both the shoulders and the taper are finished the same distance from the hole in each case4 ,the connection of the bracket 7to which the templet arm is attached7 with the stop-rod is clearly shown in ,fig4 #cc4 ,this bracket can either be locked to the ways or adjusted to slide when the stop-rod is moved4 ,illustration3 ,fig4 #ce4 ,first and ,second ,operations on ,automobile ,transmission ,shaft--,lo-swing ,lathe ,the part illustrated in ,fig4 #ce is an automobile transmission shaft4 ,in this particular case1 cylindrical1 tapering and spherical surfaces are turned4 ,the upper view shows1 diagrammatically1 the arrangement of the tools and work for the first operation4 ,after the shaft is spotted at ,a for the steadyrest1 the straight part ,c and the collar ,b are sized with tools ,s and ,r which are mounted on the left-hand carriage4 ,a concave groove is then cut in collar ,b by tool ,r1 after which spherical end ,d is formed by a special attachment mounted on the right-hand carriage4 ,this attachment is the same1 in principle1 as the regular taper-turning attachment1 the substitution of a circular templet ,t for the straight kind used on taper work being the only practical difference4 ,illustration3 ,fig4 #cf4 ,axle ,end turned in ,one ,traverse of the ,five ,tools shown ,after the surfaces mentioned have been finished on a number of pieces1 the work is reversed and the tools changed as shown by the lower view4 ,the first step in the second operation is to turn the body ,e of the shaft with the tool ,t on the left-hand carriage4 ,the taper ,f and the straight part ,g are then finished1 which completes the turning4 ,it will be noted that in setting up the machine for this second operation1 it is arranged for taper turning by simply replacing the circular templet with the straight one shown4 ,when this taper attachment is not in use1 the swiveling arm ,m1 which is attached to a bracket1 is swung out of the way4 ,the method of driving this shaft is worthy of note4 ,a dog having two driving arms each of which bears against a pin ,n that passes through a hole in the spindle is used4 ,as the ends of this pin1 against which the dog bears1 are beveled in opposite directions1 the pin turns in its hole when the dog makes contact with it and automatically adjusts itself against the two driving members of the dog4 ,the advantage of driving by a two-tailed dog1 as most mechanics know1 is in equalizing the tendency to spring slender parts while they are being turned4 ,illustration3 ,fig4 #cg4 ,lathe ,knurling ,tool having ,three ,pairs of ,knurls--,coarse1 ,medium and ,fine ,in ,fig4 #cf another turning operation on a lathe of this type is shown1 the work in this case being a rear axle for a motor truck4 ,the turning of this part is a good example of that class of work where the rapid removal of metal is the important feature4 ,as the engraving shows1 the stock1 prior to turning1 is #c-a_/b inches in diameter and it is reduced to a minimum diameter of #a-a_/af inch4 ,this metal is turned off with one traverse of the carriage or by one passage of the five tools1 and the weight of the chips removed from each end of the axle is approximately #ab pounds4 ,the time required for the actual turning is about #i minutes1 while the total time for the operation1 which includes placing the heavy piece in the machine1 turning1 and removing the work from the lathe1 is #ab minutes4 ,the axle revolves1 while being turned1 at #aaj revolutions per minute and a feed equivalent to #a inch of tool travel to #fj revolutions of the work is used4 ,it will be noticed that the taper attachment is also employed on this part1 the taper being turned by the second tool from the left4 ,as the axle is equipped with roller bearings1 it was found desirable to finish the bearing part by a separate operation2 therefore1 in the operation shown the axle is simply roughed down rather close to the finished dimensions1 leaving enough material for a light finishing cut4 ,knurling in the ,lathe4--,knurling is done either to provide a rough surface which can be firmly gripped by the hand or for producing an ornamental effect4 ,the handles of gages and other tools are often knurled1 and the thumb-screws used on instruments1 etc41 usually have knurled edges4 ,a knurled surface consists of a series of small ridges or diamond-shaped projections1 and is produced in the lathe by the use of a tool similar to the one shown in ,fig4 #cg1 this being one of several different designs in common use4 ,the knurling is done by two knurls ,a and ,b having teeth or ridges which incline to the right on one knurl and to the left on the opposite knurl1 as shown by the end view4 ,when these two knurls are pressed against the work as the latter revolves1 one knurl forms a series of left-hand ridges and the other knurl right-hand ridges1 which cross and form the diamond-shaped knurling which is generally used4 ,if the surface to be knurled is wider than the knurls1 the power feed of the lathe should be engaged and the knurling tool be traversed back and forth until the diamond-shaped projections are well formed4 ,to prevent forming a double set of projections1 feed the knurl in with considerable pressure at the start1 then partially relieve the pressure before engaging the power feed4 ,use oil when knurling4 ,the knurls commonly used for lathe work have spiral teeth and ordinarily there are three classes1 known as coarse1 medium and fine4 ,the medium pitch is generally used4 ,the teeth of coarse knurls have a spiral angle of #cf degrees and the pitch of the knurled cut 7measured parallel to the axis of the work7 should be about #h per inch4 ,for medium knurls1 the spiral angle is #bi-a_/b degrees and the pitch1 measured as before1 is #ab per inch4 ,for fine knurls1 the spiral angle is #be-c_/d degrees and the pitch #bj per inch4 ,the knurls should be about #c_/d inch in diameter and #c_/h inch wide4 ,when made to these dimensions1 coarse knurls have #cd teeth2 medium1 #ej teeth2 and fine knurls1 #hj teeth4 ,illustration3 ,fig4 #ch4 ,hendey ,relieving ,attachment applied to a ,lathe ,the particular tool illustrated in ,fig4 #cg has three pairs of knurls of coarse1 medium and fine pitch4 ,these are mounted in a revolving holder which not only serves to locate the required set of knurls in the working position1 but enables each knurl to bear against the surface with equal pressure4 ,concave knurls are sometimes used for knurling rounded edges on screw heads1 etc4 ,relieving ,attachment4--,some lathes1 particularly those used in toolrooms1 are provided with relieving attachments which are used for backing off the teeth of milling cutters1 taps1 hobs1 etc4 ,if a milling cutter of special shape is to be made1 the cutter blank is first turned to the required form with a special tool having a cutting edge that corresponds with the shape or profile of the cutter to be made4 ,the blank is then fluted or gashed to form the teeth1 after which the tops of the teeth are relieved or backed off to provide clearance for the cutting edges4 ,the forming tool used for turning the blank is set to match the turned surface1 and the teeth are backed off as the result of a reciprocating action imparted to the toolslide by the relieving attachment4 ,the motion of the toolslide is so adjusted that the tool will meet the front of each tooth and the return movement begin promptly after the tool leaves the back end of the tooth4 ,illustration3 ,fig4 #ci4 ,relieving a ,formed ,cutter ,these attachments differ somewhat in their construction and arrangement but the principle of their operation is similar4 ,fig4 #ch shows a ,hendey relieving attachment applied to a lathe4 ,a bracket carrying the gearing ,a through which the attachment is driven is mounted upon the main gear box of the lathe1 and the special slide ,b1 which is used when relieving1 is placed on the cross-slide after removing the regular compound rest4 ,the gears at ,a are changed to suit the number of flutes or gashes in the cutter1 tap or whatever is to be relieved4 ,if we assume that the work is a formed milling cutter having nine teeth1 then with this particular attachment1 a gear having #ij teeth would be placed on the stud and a #dj-tooth gear on the cam-shaft1 the two gears being connected by a #fj-tooth intermediate gear4 ,with this combination of gearing1 the toolslide would move in and out nine times for each revolution of the work1 so that the tool could back off the top of each tooth4 7,the gearing to use for various numbers of flutes is shown by an index plate on the attachment47 ,the amount of relief is varied to suit the work being done1 by means of a toothed coupling which makes it possible to change the relative position between the eccentric which actuates the toolslide and the cam lever1 thereby lengthening or shortening the reciprocating travel of the tool4 ,illustration3 ,fig4 #dj4 ,relieving ,side of ,angular ,milling ,cutter ,application of ,relieving ,attachment4--,some typical examples of the kind of work for which the relieving attachment is used are shown in ,figs4 #ci to #db1 inclusive4 ,fig4 #ci shows how a formed milling cutter is relieved4 ,the toolslide is set at right angles to the axis of the work1 and the tool moves in as each tooth passes1 and out while crossing the spaces or flutes between the teeth4 ,as the result of this movement1 the tops of the teeth are backed off eccentrically but the form or shape is the same from the front to the back of the tooth2 hence1 a cutter that has been relieved in this way can be ground repeatedly without changing the profile of the teeth1 provided the faces are ground so as to lie in a radial plane4 ,when relieving1 the cutting speed should be much less than when turning in order to give the toolslide time to operate properly4 ,a maximum of #ahj teeth per minute is recommended1 and1 if wide forming tools are used1 it might be advisable to reduce the speed so low that only #h teeth per minute would be relieved4 ,it is also essential to use a tool having a keen edge1 and the toolslide should work freely but be closely adjusted to the dovetail of the lower slide4 ,before beginning to back off the teeth1 it is a good plan to color the work either by heating it or dipping into a strong solution of copper sulphate4 ,this will enable one to see plainly the cutting action of the tool in order to stop relieving at the proper time4 ,illustration3 ,fig4 #da4 ,relieving a ,right-hand ,tap ,fig4 #dj shows a method of relieving the teeth of an angular cutter4 ,for an operation of this kind the toolslide is swiveled around at right angles to the side that is to be relieved4 ,by the use of an additional universal joint and bearing to permit the toolslide to be swung to a #ij-;degree angle1 the teeth of counterbores1 etc41 can be relieved on the ends4 ,when the attachment is used for relieving inside work1 such as hollow mills and threading dies1 the eccentric which controls the travel of the toolslide is set so that the relieving movement is away from the axis of the cutter instead of toward it4 ,this change is made by the toothed coupling previously referred to1 which connects the cam lever and oscillating shaft1 the latter being turned beyond the zero mark in a clockwise direction as far as is necessary to obtain the desired amount of travel4 ,for internal work it is also necessary to change the position of the opposing spring of the toolslide1 so that it will press against the end of the slide and prevent the tool from jumping into the work4 ,illustration3 ,fig4 #db4 ,relieving a ,hob having ,spiral ,flutes ,fig4 #da shows how a right-hand tap is relieved4 ,the ordinary practice is to first set the tool the same as for cutting a thread4 ,the motion of the toolslide is then adjusted so that the tool on the forward stroke will meet the front of each tooth1 and start back as soon as the tool leaves the end of the land or top of the tooth4 ,taps having a left-hand thread can be relieved by two different methods4 ,with the first method the cut starts at the cutting edge of each tooth1 and ends at the heel1 the tool moving in toward the center of the work4 ,with the second method1 the cut begins at the heel and discontinues at the cutting edge1 the tool being drawn away from the work during the cut4 ,when using the first method the tap must be placed with the point toward the headstock1 the shank end being supported by the tailstock center4 ,this is done by providing an extension or blank end at the point of the tap long enough to hold the driving dog4 ,with the second method1 the tap is held between centers the same as one having a right-hand thread1 but the travel of the toolslide is set the same as for inside relief4 ,relieving ,hobs or ,taps ,having ,spiral ,flutes4--,with this attachment1 taps or hobs having spiral or helical flutes can also be relieved4 7,a spiral flute is preferable to one that is parallel to the axis1 because with the former the tool has cutting edges which are square with the teeth2 this is of especial importance when the lead of the hob or tap thread is considerable47 ,when relieving work having spiral flutes 7as illustrated in ,fig4 #db71 the lead of the spiral and the gears necessary to drive the attachment are first determined4 ,after the attachment is geared for the number of flutes and to compensate for the spiral1 the lead-screw is engaged and the backing-off operation is performed the same as though the flutes were straight4 ,the carriage should not be disengaged from the lead-screw after starting the cut1 the tool being returned by reversing the lathe4 ,when gearing the attachment for relieving a tap or hob having spiral flutes1 the gears are not selected for the actual number of flutes around the circumference but for a somewhat larger number which depends upon the lead of the hob thread and the lead of the spiral flutes4 ,let us assume that a hob has #f spiral flutes and that the attachment is geared for that number4 ,the result would be that as the tool advanced along the thread1 it would not keep in step with the teeth because the faces of the teeth lie along a spiral 7or helix which is the correct name for this curve72 in other words1 the tool would soon be moving in too late to begin cutting at the proper time1 and to compensate for this1 the attachment is geared so that the tool will make a greater number of strokes per revolution of the work than the actual number of flutes around the circumference4 ,with this attachment1 the two gears listed on the index plate for the actual number of flutes are selected1 and then two compensating gears are added1 thus forming a compound train of gearing4 ,the ratio ,r of these compensating gears is determined as follows3 r #a ,r ------- r in which r ,l _/ l2 ,l lead of spiral2 l lead of hob thread4 ,for example1 if a hob has a pitch circumference of #c4be1 a single thread of #j4ge inch lead1 and #f spiral flutes1 what compensating gears would be required8 ,the lead ,l of the spiral flutes is first determined by dividing the square of the circumference ,c of the hob at the pitch line by the lead l of the hob thread4 ,thus lead ,l ,c#b_/l1 or1 in this case1 ,l #c4beb_/j4ge #ad inches1 approximately4 ,then r #ad _/ #j4ge #ah-b_/c4 ,inserting these values in the formula for ratio ,r1 #ah-b_/c #a #ai-b_/c #ai-b_/c x #c #ei ,r ---------- ------ ---------- -- #ah-b_/c #ah-b_/c #ah-b_/c x #c #ef ,hence1 the compensating gears will have #ef and #ei teeth1 respectively1 the latter being the driver4 ,as the gears for #f flutes listed on the regular index plate are1 stud-gear #fj teeth1 cam-shaft gear #dj teeth1 the entire train of gears would be as follows3 ,gear on stud1 #fj2 driven intermediate gear1 #ef2 driving intermediate gear1 #ei2 cam-shaft gear1 #dj4 ,it will be understood that the position of the driving gears or the driven gears can be transposed without affecting the ratio4 ,classes of ,fits ,used in ,machine ,construction4--,in assembling machine parts it is necessary to have some members fit together tightly1 whereas other parts such as shafts1 etc41 must be free to move or revolve with relation to each other4 ,the accuracy required for a fitting varies for different classes of work4 ,a shaft that revolves in its bearing must be slightly smaller than the bearing so that there will be room for a film of lubricant4 ,a crank-pin that must be forced into the crank-disk is made a little larger in diameter than the hole1 to secure a tight fit4 ,when a very accurate fitting between two cylindrical parts that must be assembled without pressure is required1 the diameter of the inner member is made as close to the diameter of the outer member as is possible4 ,in ordinary machine construction1 five classes of fits are used1 viz2 running fit1 push fit1 driving fit1 forced fit and shrinkage fit4 ,the running fit1 as the name implies1 is employed when parts must rotate2 the push fit is not sufficiently free to rotate2 the other classes referred to are used for assembling parts that must be held in fixed positions4 ,forced ,fits4--,this is the term used when a pin1 shaft or other cylindrical part is forced into a hole of slightly smaller diameter1 by the use of a hydraulic press or other means4 ,as a rule1 forced fits are restricted to parts of small and medium size1 while shrinkage fits have no such limitations and are especially applicable when a maximum grip is desired1 or when 7as in the construction of ordnance7 accurate results as to the intensity of stresses produced in the parts united are required4 ,the proper allowance for a forced fit depends upon the mass of metal surrounding the hole1 the size of the work1 the kind and quality of the material of which the parts are composed and the smoothness and accuracy of the pin and bore4 ,when a pin or other part is pressed into a hole a second time1 the allowance for a given tonnage should be diminished somewhat because the surface of the bore is smoother and the metal more compact4 ,the pressure required in assembling a forced fit will also vary for cast hubs of the same size1 if they are not uniform in hardness4 ,then there is the personal factor which is much in evidence in work of this kind2 hence1 data and formulas for forced fit allowances must be general in their application4 ,allowance for ,forced ,fits4--,the allowance per inch of diameter usually ranges from #j4jja inch to #j4jjbe inch1 #j4jjae being a fair average4 ,ordinarily1 the allowance per inch decreases as the diameter increases2 thus the total allowance for a diameter of #b inches might be #j4jjd inch1 whereas for a diameter of #h inches the total allowance might not be over #j4jji or #j4jaj inch4 ,in some shops the allowance is made practically the same for all diameters1 the increased surface area of the larger sizes giving sufficient increase in pressure4 ,the parts to be assembled by forced fits are usually made cylindrical1 although sometimes they are slightly tapered4 ,the advantages of the taper form are that the possibility of abrasion of the fitted surfaces is reduced2 that less pressure is required in assembling2 and that the parts are more readily separated when renewal is required4 ,on the other hand1 the taper fit is less reliable1 because if it loosens1 the entire fit is free with but little axial movement4 ,some lubricant1 such as white lead and lard oil mixed to the consistency of paint1 should be applied to the pin and bore before assembling1 to reduce the tendency of abrasion4 ,allowances for ,different ,classes of ,fits 7,newall ,engineering ,co47 ---------------------------------------- --------------------------- ,tolerances in ,standard ,holes#a ,class---------------------------------- ----------------------- ,nominal ,up to #i_/af-a #a-a_/af- #b-a_/af- #c-a_/af- ,diameters #a_/b #b #c #d ---------------------------------------- ---------------------- ,high ,limit #j4jjjb #j4jjje #j4jjjg #j4jjaj #j4jjaj ,a ,low ,limit -#j4jjjb -#j4jjjb -#j4jjjb -#j4jjje -#j4jjje ,tolerance #j4jjjd #j4jjjg #j4jjji #j4jjae #j4jjae ---------------------------------------- ---------------------- ,high ,limit #j4jjje #j4jjjg #j4jjaj #j4jjab #j4jjae ,b ,low ,limit -#j4jjje -#j4jjje -#j4jjje -#j4jjjg -#j4jjjg ,tolerance #j4jjaj #j4jjab #j4jjae #j4jjai #j4jjbb ---------------------------------------- ---------------------- ,allowances for ,forced ,fits ---------------------------------------- ---------------------- ,high ,limit #j4jjaj #j4jjbj #j4jjdj #j4jjfj #j4jjhj ,f ,low ,limit #j4jjje #j4jjae #j4jjcj #j4jjde #j4jjfj ,tolerance #j4jjje #j4jjje #j4jjaj #j4jjae #j4jjbj ---------------------------------------- ---------------------- ,allowances for ,driving ,fits ---------------------------------------- ---------------------- ,high ,limit #j4jjje #j4jjaj #j4jjae #j4jjbe #j4jjcj ,d ,low ,limit #j4jjjb #j4jjjg #j4jjaj #j4jjae #j4jjbj ,tolerance #j4jjjc #j4jjjc #j4jjje #j4jjaj #j4jjaj ---------------------------------------- ---------------------- ,allowances for ,push ,fits ---------------------------------------- ---------------------- ,high ,limit -#j4jjjb -#j4jjjb -#j4jjjb -#j4jjje -#j4jjje ,p ,low ,limit -#j4jjjg -#j4jjjg -#j4jjjg -#j4jjaj -#j4jjaj ,tolerance #j4jjje #j4jjje #j4jjje #j4jjje #j4jjje ---------------------------------------- ---------------------- ,allowances for ,running ,fits#b ---------------------------------------- ---------------------- ,high ,limit -#j4jjaj -#j4jjab -#j4jjag -#j4jjbj -#j4jjbe ,x ,low ,limit -#j4jjbj -#j4jjbg -#j4jjce -#j4jjdb -#j4jjej ,tolerance #j4jjaj #j4jjae #j4jjah #j4jjbb #j4jjbe ,high ,limit -#j4jjjg -#j4jjaj -#j4jjab -#j4jjae -#j4jjbj ,y ,low ,limit -#j4jjab -#j4jjbj -#j4jjbe -#j4jjcj -#j4jjce ,tolerance #j4jjje #j4jjaj #j4jjac #j4jjae #j4jjae ,high ,limit -#j4jjje -#j4jjjg -#j4jjjg -#j4jjaj -#j4jjaj ,z ,low ,limit -#j4jjjg -#j4jjab -#j4jjae -#j4jjbj -#j4jjbb ,tolerance #j4jjjb #j4jjje #j4jjjh #j4jjaj #j4jjab ---------------------------------------- ---------------------- #a ,tolerance is provided for holes1 which ordinary standard reamers can produce1 in two grades1 ,classes ,a and ,b1 the selection of which is a question for the user's decision and dependent upon the quality of the work required2 some prefer to use ,class ,a as working limits and ,class ,b as inspection limits4 #b ,running fits1 which are the most commonly required1 are divided into three grades3 ,class ,x for engine and other work where easy fits are wanted2 ,class ,y for high speeds and good average machine work2 ,class ,z for fine tool work4 ,pressure for ,forced ,fits4--,the pressure required for assembling cylindrical parts depends not only upon the allowance for the fit1 but also upon the area of the fitted surfaces1 the pressure increasing in proportion to the distance that the inner member is forced in4 ,the approximate ultimate pressure in pounds can be determined by the use of the following formula in conjunction with the accompanying table of ,pressure ,factors4 ,pressure ,factors ---------------------------------------- -------------- ,diam-,pres-,diam-,pres-,diam-,pres-,dia m- ,pres- ,diam- ,pres- eter1sure eter1sure eter1sure eter1 sure eter1 sure ,in- ,fac- ,in- ,fac- ,in- ,fac- ,in- ,fac- ,in- ,fac- ches tor ches tor ches tor ches tor ches tor ---------------------------------------- -------------- #a #ejj #c-a_/b #acb #f #ge #i #dh4g #ad #cj4e #a-a_/d #cie #c-c_/d #abc #f-a_/d #gb #i-a_/b #df4j #ad-a_/b #bi4d #a-a_/b #cbe #d #aae #f-a_/b #fi #aj #dc4e #ae #bh4c #a-c_/d #bgf #d-a_/d #ajh #f-c_/d #ff #aj-a_/b #da4c #ae-a_/b #bg4d #b #bdj #d-a_/b #aja #g #fd #aa #ci4c #af #bf4e #b-a_/d #bab #d-c_/d #if #g-a_/d #fa #aa-a_/b #cg4e #af-a_/b #be4f #b-a_/b #ahi #e #ia #g-a_/b #ei #ab #ce4i #ag #bd4h #b-c_/d #aga #e-a_/d #hf #g-c_/d #eg #ab-a_/b #cd4d #ag-a_/b #bd4a #c #aef #e-a_/b #hb #h #ee #ac #cc4j #ah #bc4d #c-a_/d #adc #e-c_/d #gh #h-a_/b #eb #ac-a_/b #ca4g 4444 4444 ---------------------------------------- -------------- ,assuming that ,a area of fitted surface2 a total allowance in inches2 ,p ultimate pressure required1 in tons2 ,f pressure factor based upon assumption that the diameter of the hub is twice the diameter of the bore1 that the shaft is of machine steel1 and the hub of cast iron1 then1 ,a x a x ,f ,p --------------- #b ,example3--,what will be the approximate pressure required for forcing a #d-;inch machine steel shaft having an allowance of #j4jjhe inch into a cast-iron hub #f inches long8 ,a #d x #c4adaf x #f #ge4ci square inches2 ,f1 for a diameter of #d inches1 #aae 7see table of ,pressure ,factors74 ,then1 ,p 7#ge4ci x #j4jjhe x #aae7_/b #cg tons1 approximately4 ,allowance for ,given ,pressure4--,by transposing the preceding formula1 the approximate allowance for a required ultimate tonnage can be determined4 ,thus1 a #b,p _/ ,,af4 ,the average ultimate pressure in tons commonly used ranges from #g to #aj times the diameter in inches4 ,assuming that the diameter of a machine steel shaft is #d inches and an ultimate pressure of about #cj tons is desired for forcing it into a cast-iron hub having a length of #e-a_/b inches1 what should be the allowance8 ,a #d x #c4adaf x #e-a_/b #fi square inches1 ,f1 for a diameter of #d inches1 #aae4 ,then1 #b x #cj a -------- #j4jjge inch4 #fi x #aae ,shrinkage ,fits4--,when heat is applied to a piece of metal1 such as iron or steel1 as is commonly known1 a certain amount of expansion takes place which increases as the temperature is increased1 and also varies somewhat with different kinds of metal1 copper and brass expanding more for a given increase in temperature than iron and steel4 ,when any part which has been expanded by the application of heat is cooled1 it contracts and resumes its original size4 ,this expansive property of metals has been taken advantage of by mechanics in assembling various machine details4 ,a cylindrical part which is to be held in position by a shrinkage fit is first turned a few thousandths of an inch larger than the hole2 the diameter of the latter is then increased by heating1 and after the part is inserted1 the heated outer member is cooled1 causing it to grip the pin or shaft with tremendous pressure4 ,general practice seems to favor a smaller allowance for shrinkage fits than for forced fits1 although in many shops the allowances are practically the same in each case1 and for some classes of work1 shrinkage allowances exceed those for forced fits4 ,in any case1 the shrinkage allowance varies to a great extent with the form and construction of the part which has to be shrunk into place4 ,the thickness or amount of metal around the hole is the most important factor4 ,the way in which the metal is distributed also has an influence on the results4 ,shrinkage allowances for locomotive driving wheel tires adopted by the ,american ,railway ,master ,mechanics ,association are as follows3 ,center diameter1 inches #ch #dd #ej #ef #fb #ff ,allowance1 inches #j4jdj #j4jdg #j4jec #j4jfj #j4jff #j4jgj ,whether parts are to be assembled by forced or shrinkage fits depends upon conditions4 ,for example1 to press a driving wheel tire over its wheel center1 without heating1 would ordinarily be a rather awkward and difficult job4 ,on the other hand1 pins1 etc41 are easily and quickly forced into place with a hydraulic press and there is the additional advantage of knowing the exact pressure required in assembling1 whereas there is more or less uncertainty connected with a shrinkage fit1 unless the stresses are calculated4 ,tests to determine the difference in the quality of shrinkage and forced fits showed that the resistance of a shrinkage fit to slippage was1 for an axial pull1 #c4ff times greater than that of a forced fit1 and in rotation or torsion1 #c4b times greater4 ,in each comparative test1 the dimensions and allowances were the same4 ,the most important point to consider when calculating shrinkage fits is the stress in the hub at the bore1 which depends chiefly upon the shrinkage allowance4 ,if the allowance is excessive1 the elastic limit of the material will be exceeded and permanent set will occur1 or1 in extreme cases1 the ultimate strength of the metal will be exceeded and the hub will burst4 ,,chapter ,,iv ,,thread ,,cutting ,,in ,,the ,,lathe ,when threads are cut in the lathe a tool t is used 7see ,fig4 #b71 having a point corresponding to the shape of the thread1 and the carriage is moved along the bed a certain distance for each revolution of the work 7the distance depending on the number of threads to the inch being cut7 by the lead-screw ,s which is rotated by gears a1 b and c1 which receive their motion from the spindle4 ,as the amount that the carriage travels per revolution of the work1 and1 consequently1 the number of threads per inch that is cut1 depends on the size of the gears a and c 7called change gears7 the latter have to be changed for cutting different threads4 ,the proper change gears to use for cutting a given number of threads to the inch is ordinarily determined by referring to a table or index plate ,i which shows what the size of gears a and c should be1 or the number of teeth each should have1 for cutting any given number of threads per inch4 ,illustration3 ,fig4 #a4 ,measuring ,number of ,threads per ,inch--,setting ,thread ,tool ,illustration3 ,fig4 #b4 ,plan and ,elevations of ,engine ,lathe ,selecting the ,change ,gears for ,thread ,cutting4--,suppose a ,v-thread is to be cut on the end of the bolt ,b1 ,fig4 #b1 having a diameter of #a-a_/d inch and seven threads per inch of length1 as shown at ,a in ,fig4 #a1 which is the standard number of threads per inch for that diameter4 ,first the change gears to use are found on plate ,i which is shown enlarged in ,fig4 #c4 ,this plate has three columns3 ,the first contains different numbers of threads to the inch1 the second the size gear to place on the spindle or stud at a 7,fig4 #b7 for different threads1 and the third the size of gear c for the lead-screw4 ,as the thread selected as an example has #g threads per inch1 gear a should have #dh teeth1 this being the number given in the second column opposite figure #g in the first4 ,by referring to the last column1 we find that the lead-screw gear should have #hd teeth4 ,these gears are selected from an assortment provided with the lathe and they are placed on the spindle and lead-screw1 respectively4 ,illustration3 ,fig4 #c4 ,index ,plate showing ,gear ,changes for ,threading ,intermediate gear b does not need to be changed as it is simply an idler for connecting gears a and c4 ,gear b is mounted on a swinging yoke ,y so that it can be adjusted to mesh properly with different gear combinations2 after this adjustment is made1 the lathe is geared for cutting #g threads to the inch4 7,the change gears of many modern lathes are so arranged that different combinations are obtained by simply shifting a lever4 ,a lathe having this quick-change gear mechanism is described in the latter part of this chapter47 ,the work ,b is placed between the centers just as it would be for turning1 with the end to be threaded turned to a diameter of #a-a_/d inch1 which is the outside diameter of the thread4 ,the ,thread ,tool4--,the form of tool used for cutting a ,v-thread is shown at ,a1 ,fig4 #d4 ,the end is ground ,v-shaped and to an angle of #fj degrees1 which corresponds to the angle of a standard ,v-thread4 ,the front or flank1 f of the tool is ground back at an angle to provide clearance1 but the top is left flat or without slope4 ,as it is very important to grind the end to exactly #fj degrees1 a gage ,g is used1 having #fj-;degree notches to which the tool-point is fitted4 ,the tool is clamped in the toolpost as shown in the plan view1 ,fig4 #b1 square with the work1 so that both sides of the thread will be cut to the same angle with the axis of the work4 ,a very convenient way to set a thread tool square is illustrated at ,b1 ,fig4 #a4 ,the thread gage is placed against the part to be threaded1 as shown1 and the tool is adjusted until the angular sides of the point bear evenly in the #fj-;degree notch of the gage4 ,the top of the tool point should be at the same height as the lathe centers1 as otherwise the angle of the thread will not be correct4 ,illustration3 ,fig4 #d4 ,thread ,tools and ,gage for testing ,angle of ,end ,cutting the ,thread4--,the lathe is now ready for cutting the thread4 ,this is done by taking several cuts1 as indicated at ,a1 ,b1 ,c and ,d in ,fig4 #e1 the tool being fed in a little farther for each successive cut until the thread is finished4 ,when these cuts are being taken1 the carriage is moved along the bed1 as previously explained1 by the lead-screw ,s1 ,fig4 #b4 ,the carriage is engaged with the lead-screw by turning lever u which causes the halves of a split nut to close around the screw4 ,the way a lathe is handled when cutting a thread is as follows3 ,after the lathe is started1 the carriage is moved until the tool-point is slightly beyond the right end of the work1 and the tool is fed in far enough to take the first cut which1 ordinarily1 would be about #a_/af inch deep4 ,the carriage is then engaged with the lead-screw1 by operating lever u1 and the tool moves to the left 7in this case #a_/g inch for each revolution of the work7 and cuts a winding groove as at ,a1 ,fig4 #e4 ,when the tool has traveled as far as the thread is wanted1 it is withdrawn by a quick turn of cross-slide handle e1 and the carriage is returned to the starting point for another cut4 ,the tool is then fed in a little farther and a second cut is taken as at ,b1 ,fig4 #e1 and this operation is repeated as at ,c and ,d until a full thread is cut or until the top of the thread is sharp4 ,the thread is then tested for size but before referring to this part of the work1 the way the carriage is returned to the starting point after each cut should be explained4 ,illustration3 ,fig4 #e4 ,thread is formed by taking a ,number of ,successive ,cuts ,when the tool is withdrawn at the end of the first cut1 if the carriage is disengaged from the lead-screw and returned by hand1 the tool may or may not follow the first cut when the carriage is again engaged with the lead-screw4 ,if the number of threads to the inch being cut is a multiple of the number on the lead-screw ,s1 then the carriage can be returned by hand and engaged with the lead-screw at random and the tool will follow the first cut4 ,for example1 if the lead-screw has six threads per inch1 and #f1 #ab1 #ah or any number of threads is being cut that is a multiple of six1 the carriage can be engaged at any time and the tool will always follow the original cut4 ,this is not the case1 however1 when the number of threads being cut is not a multiple of the number on the lead-screw4 ,one method of bringing the carriage back to the starting point1 when cutting threads which are not multiples1 is to reverse the lathe 7by shifting the overhead driving belts7 in order to bring the tool back to the starting point without disengaging the carriage2 in this way the tool is kept in the same relation to the work1 and the carriage is not disengaged from the lead-screw until the thread is finished4 ,this is a good method when cutting short threads having a length of say two or three inches2 but when they are longer1 and especially when the diameter is comparatively large 7which means a slower speed71 it is rather slow as considerable time is wasted while the tool is moving back to its starting point4 ,this is due to the fact that the carriage is moved slowly by the lead-screw1 but when disengaged1 it can be traversed quickly by turning handle d1 ,fig4 #b4 ,a method of returning the carriage by hand when the number of threads being cut is not a multiple of the number on the lead-screw is as follows3 ,the tool is moved a little beyond the right end of the work and the carriage or split nut is engaged with the lead-screw4 ,the lathe is then turned forward by hand to take up any lost motion1 and a line is made on the lathe bed showing the position of the carriage4 ,the positions of the spindle and lead-screw are also marked by chalking a tooth on both the spindle and lead-screw gears1 which happens to be opposite a corner or other point on the bed4 ,after a cut is taken1 the carriage is returned by hand to the original starting point as shown by the line on the bed1 and is again engaged when the chalk marks show that the spindle and lead-screw are in their original position2 the tool will then follow the first cut4 ,if the body of the tailstock is moved against the bridge of the carriage before starting the first cut1 the carriage can be located for each following cut by moving it back against the tailstock1 and it will not be necessary to have a line on the bed4 ,illustration3 ,fig4 #f4 ,indicator used when ,cutting ,threads ,indicator or ,chasing ,dial for ,catching ,threads4--,on some lathes there is an indicator for catching threads1 as this is called in shop language4 ,this is a simple device attached to the carriage and consists of a graduated dial ,d and a worm-wheel ,w 7see ,figs4 #b and #f7 which meshes with the lead-screw1 so that the dial is revolved by the lead-screw when the carriage is stationary1 and when the carriage is moved by the screw1 the dial remains stationary4 ,the indicator is used by engaging the carriage when one of the graduation lines is opposite the arrow mark2 after a cut is taken the carriage is returned by hand and when one of the graduation lines again moves opposite the arrow1 the half-nuts are thrown into mesh1 as before1 and this is repeated for each successive cut1 thus causing the tool to always come right with the thread4 ,if the number of threads per inch is even1 engagement can be made when any line is opposite the arrow1 but for odd numbers such as #c1 #g1 #i1 #aa1 etc41 one of the four long or numbered lines must be used4 ,of course1 if the thread being cut is a multiple of the number on the lead-screw1 engagement can be made at any time1 as previously mentioned4 ,principle of the ,thread ,indicator4--,the principle upon which the thread indicator operates is as follows3 ,the number of teeth in worm-wheel ,w is some multiple of the number of threads per inch of the lead-screw1 and the number of teeth in the worm-wheel1 divided by the pitch of the screw1 equals the number of graduations on the dial4 ,for example1 if the lead-screw has six threads per inch1 the worm-wheel could have twenty-four teeth1 in which case the dial would have four divisions1 each representing an inch of carriage travel1 and by sub-dividing the dial into eighths 7as shown7 each line would correspond to #a_/b inch of travel4 ,the dial1 therefore1 would enable the carriage to be engaged with the lead-screw at points equal to a travel of one-half inch4 ,to illustrate the advantage of this suppose ten threads per inch are being cut and 7with the lathe stationary7 the carriage is disengaged and moved #a_/f inch or one thread on the lead-screw2 the tool point will also have moved #a_/f inch1 but it will not be opposite the next thread groove in the work as the pitch is #a_/aj inch4 ,if the carriage is moved another thread on the lead-screw1 or #b_/f inch1 the tool will still be out of line with the thread on the work1 but when it has moved three threads1 or #a_/b inch1 the tool will then coincide with the original cut because it has passed over exactly five threads4 ,this would be true for any number of threads per inch that is divisible by #b4 ,if the thread being cut had nine threads per inch or any other odd number1 the tool would only coincide with the thread at points #a inch apart4 ,therefore1 the carriage can only be engaged when one of the four graduations representing an inch of travel is opposite the arrow1 when cutting odd threads2 whereas even numbers can be caught by using any one of the eight lines4 ,this indicator can also be used for catching fractional threads4 ,as an illustration1 suppose #aa-a_/b threads per inch are to be cut1 and the carriage is engaged for the first cut when graduation line #a is opposite the arrow2 engagement would then be made for each successive cut1 when either line #a or #c were opposite the arrow1 or in other words at spaces equal to a carriage movement of #b inches4 ,as the use of the indicator when cutting fractional threads is liable to result in error1 it is better to keep the half-nuts in engagement and return the carriage by reversing the lathe4 ,replacing ,sharpened ,thread ,tool4--,if it is necessary to sharpen the thread tool before the thread is finished1 it should be reset square with the work by testing with the thread gage as at ,b1 ,fig4 #a4 ,the carriage is then engaged with the lead-screw and the lathe is turned forward to bring the tool opposite the partly finished thread and also to take up any backlash or lost motion in the gears or half-nut4 ,if the tool-point is not in line with the thread groove previously cut1 it can be shifted sidewise by feeding the compound rest ,e in or out1 provided the latter is set in an angular position as shown in the plan view1 ,fig4 #b4 ,if the thread tool is ground flat on the top as at ,a1 ,fig4 #d1 it is not a good tool for removing metal rapidly as neither of its two cutting edges has any slope4 ,in order to give each cutting edge a backward slope1 it would be necessary to grind the top surface hollow or concave1 which would be impracticable4 ,when a course thread is to be cut1 a tool shaped as at ,b can be used to advantage for rough turning the thread groove1 which is afterward finished to the correct depth and angle by tool ,a4 ,this roughing tool is ground with a backward slope from the point and the latter is rounded to make it stronger4 ,use of ,compound ,rest for ,thread ,cutting4--,another form of thread tool is shown at ,a1 ,fig4 #g1 which is very good for cutting ,v-threads especially of coarse pitch4 ,when this tool is used1 the compound rest ,e is set to an angle of #cj degrees1 as shown1 and it is fed in for the successive cuts by handle w in the direction indicated by the arrow4 ,it will be seen that the point a of the tool moves at an angle of #fj degrees with the axis of the work1 thus forming one side of the thread1 and the cutting edge a--b1 which can be set as shown at ,b1 forms the opposite side and does all the cutting4 ,as this edge is given a backward slope1 as shown1 it cuts easily and enables threading operations to be performed quickly4 ,threads cut in this way are often finished by taking a light cut with a regular thread tool4 ,the cutting edge a--b is ground to an angle of #fj degrees 7or slightly less1 if anything7 with the side1 as shown by sketch ,a4 ,when cutting threads in steel or wrought iron1 some sort of lubricant is usually applied to the tool to preserve the cutting end and give a smooth finish to the thread4 ,lard oil or a mixture of equal parts of lard oil and paraffin oil are often used for this purpose4 ,if the thread is small1 the lubricant may be applied from an ordinary oil can1 but when cutting comparatively large threads1 it is better to have a stream of oil constantly playing upon the tool-point4 ,this constant flow may be obtained by mounting a can having a spout leading to the tool1 on a bracket at the rear of the carriage4 ,illustration3 ,fig4 #g4 ,cutting ,thread by using ,compound ,rest ,illustration3 ,fig4 #h4 7,a7 ,v-thread4 7,b7 ,u4 ,s4 ,standard ,thread4 7,c7 ,square ,thread4 7,d7 ,left-hand ,thread4 7,e7 ,double ,square ,thread4 7,f7 ,triple ,square ,thread ,threads ,commonly ,used4--,three forms of threads or screws which are in common use are shown in ,fig4 #h2 these are the ,v-thread 7,a71 the ,u4 ,s4 standard 7,b71 and the square thread 7,c74 ,the shapes of these threads are shown by the sectioned parts4 ,the ,v-thread has straight sides which incline at an angle of #fj degrees with each other and at the same angle with the axis of the screw4 ,the ,u4 ,s4 standard thread is similar to the ,v-thread except that the top of the thread and bottom of the groove is left flat1 as shown1 and the width of these flats is made equal to #a_/h of the pitch4 ,the square thread is square in section1 the width a1 depth b and space c being all equal4 ,all of these threads are right-hand1 which means that the grooves wind around to the right so that a nut will have to be turned toward the right to enter it on the thread4 ,a left-hand thread winds in the other direction1 as shown at ,d1 and a nut is screwed on by turning it to the left4 ,multiple ,threads4--,threads1 in addition to being right-and left-handed1 are single1 as at ,a1 ,b1 ,c and ,d1 double1 as at ,e1 and triple1 as at ,f1 and for certain purposes quadruple threads or those of a higher multiple are employed4 ,a double thread is different from a single thread in that it has two grooves1 starting diametrically opposite1 whereas a triple thread has three grooves cut as shown at ,f4 ,the object of these multiple threads is to obtain an increase in lead without weakening the screw4 ,for example1 the threads shown at ,c and ,e have the same pitch p but the lead l of the double-threaded screw is twice that of the one with a single thread so that a nut would advance twice as far in one revolution1 which is often a very desirable feature4 ,to obtain the same lead with a single thread1 the pitch would have to be double1 thus giving a much coarser thread1 which would weaken the screw1 unless its diameter were increased4 7,the lead is the distance l that one thread advances in a single turn1 or the distance that a nut would advance in one turn1 and it should not be confused with the pitch p1 which is the distance between the centers of adjacent threads4 ,obviously the lead and pitch of a single thread are the same47 ,cutting a ,u4 ,s4 ,standard ,thread4--,the method of cutting a ,u4 ,s4 standard thread is the same as described for a ,v-thread1 so far as handling the lathe is concerned4 ,the thread tool must correspond1 of course1 to the shape of a ,u4 ,s4 standard thread4 ,this tool is first ground to an angle of #fj degrees1 as it would be for cutting a ,v-thread1 and then the point is made flat as shown in ,fig4 #i4 ,as will be recalled1 the width of this flat should be equal to #a_/h of the pitch4 ,by using a gage like the one shown at ,g1 the tool can easily be ground for any pitch1 as the notches around the periphery of the gage are marked for different pitches and the tool-point is fitted into the notch corresponding to the pitch wanted4 ,if such a gage is not available1 the width of the flat at the point can be tested by using1 as a gage1 a ,u4 ,s4 standard tap of the same pitch as the thread to be cut4 ,when cutting the thread1 the tool is set square with the blank1 and a number of successive cuts are taken1 the tool being fed in until the width w of the flat at the top of the thread is equal to the width at the bottom4 ,the thread will then be the right size provided the outside diameter ,d is correct and the tool is of the correct form4 ,as it would be difficult to measure the width of this flat accurately1 the thread can be tested by screwing a standard nut over it if a standard thread is being cut4 ,if it is being fitted to a tapped hole1 the tap itself is a very convenient gage to use1 the method being to caliper the tap and then compare its size with the work4 ,illustration3 ,fig4 #i4 ,u4 ,s4 ,standard ,thread1 ,thread ,tool1 and ,gage ,a good method of cutting a ,u4 ,s4 standard thread to a given size is as follows3 ,first turn the outside of the blank accurately to diameter ,d1 and then turn a small part of the end to diameter r of the thread at the root4 ,the finishing cut for the thread is then taken with the tool point set to just graze diameter r4 ,if ordinary calipers were set to diameter r and measurements taken in the thread groove1 the size would be incorrect owing to the angularity of the groove1 which makes it necessary to hold the calipers at an angle when measuring4 ,to determine the root diameter divide #a4bii by the number of threads per inch and subtract the quotient from the outside diameter4 ,expressing this rule as a formula1 _/#a4bii r ,d - 7 ----- 7 ,n _/ in which ,d equals outside diameter2 ,n1 the number of threads per inch2 and r1 the root diameter4 ,the number #a4bii is a constant that is always used4 ,illustration3 ,fig4 #aj4 ,end ,view of ,lathe ,headstock ,cutting a ,left-hand ,thread4--,the only difference between cutting left-hand and right-hand threads in the lathe is in the movement of the tool with relation to the work4 ,when cutting a right-hand thread1 the tool moves from right to left1 but this movement is reversed for left-hand threads because the thread winds around in the opposite direction4 ,to make the carriage travel from left to right1 the lead-screw is rotated backwards by means of reversing gears a and b 7,fig4 #aj7 located in the headstock4 ,either of these gears can be engaged with the spindle gear by changing the position of lever ,r4 ,when gear a is in engagement1 as shown1 the drive from the spindle to gear c is through gears a and b1 but when lever ,r is raised thus shifting b into mesh1 the drive is direct and the direction of rotation is reversed4 ,the thread is cut by starting the tool at a1 ,fig4 #h1 instead of at the end4 ,illustration3 ,fig4 #aa4 ,end of ,square ,thread ,tool1 and ,graphic ,method of ,determining ,helix ,angle of ,thread ,cutting a ,square ,thread4--,the form of tool used for cutting a square thread is shown in ,fig4 #aa4 ,the width w is made equal to one-half the pitch of the thread to be cut and the end ,e is at an angle with the shank1 which corresponds to the inclination x--y of the threads4 ,this angle ,a depends upon the diameter of the screw and the lead of the thread2 it can be determined graphically by drawing a line a--b equal in length to the circumference of the screw to be cut1 and a line b--c1 at right angles1 equal in length to the lead of the thread4 ,the angle alpha between lines a--b and a--c will be the required angle ,a4 7,see end view of thread tool74 ,it is not necessary to have this angle accurate1 ordinarily1 as it is simply to prevent the tool from binding against the sides of the thread4 ,the end of a square thread tool is shown in section to the right1 to illustrate its position with relation to the threads4 ,the sides e and e#a are ground to slope inward1 as shown1 to provide additional clearance4 ,when cutting multiple threads1 which1 owing to their increased lead1 incline considerably with the axis of the screw1 the angles for each side of the tool can be determined independently as follows3 ,draw line a--b equal in length to the circumference of the thread1 as before1 to obtain the required angle f of the rear or following side e#a2 the angle l of the opposite or leading side is found by making a--b equal to the circumference at the root of the thread4 ,the tool illustrated is for cutting right-hand threads2 if it were intended for a left-hand thread1 the end1 of course1 would incline in the opposite direction4 ,the square thread is cut so that the depth d is equal to the width4 ,when threading a nut for a square thread screw1 it is the usual practice to use a tool having a width slightly greater than one-half the pitch1 to provide clearance for the screw1 and the width of a tool for threading square-thread taps to be used for tapping nuts is made slightly less than one-half the pitch4 ,cutting ,multiple ,threads4--,when a multiple thread is to be cut1 such as a double or triple thread1 the lathe is geared with reference to the number of single threads to the inch4 ,for example1 the lead of the double thread1 shown at ,b1 ,fig4 #ab1 is one-half inch1 or twice the pitch1 and the number of single threads to the inch equals #a _/ #a_/b #b4 ,therefore1 the lathe is geared for cutting two threads per inch4 ,the first cut is taken just as though a single thread were being cut1 leaving the work as shown at ,a4 ,when this cut is finished the work is turned one-half a revolution 7for a double thread7 without disturbing the position of the lead-screw or carriage1 which brings the tool midway between the grooves of the single thread as indicated by dotted lines4 ,the second groove is then cut1 producing a double thread as shown at ,b4 ,in the case of a triple thread1 the work would be indexed one-third of a revolution after turning the first groove1 and then another third revolution to locate the tool for cutting the last groove4 ,similarly1 for a quadruple thread1 it would be turned one-quarter revolution after cutting each successive groove or thread4 ,there are different methods of indexing the work when cutting multiple threads1 in order to locate the tool in the proper position for cutting another thread groove4 ,some machinists1 when cutting a double thread1 simply remove the work from the lathe and turn it one-half a revolution by placing the tail of the driving dog in the opposite slot of the faceplate4 ,this is a very simple method1 but if the slots are not directly opposite or #ahj degrees apart1 the last thread will not be central with the first4 ,another and better method is to disengage the idler gear from the gear on the stud1 turn the spindle and work one-half1 or one-third1 of a revolution1 as the case might be1 and then connect the gears4 ,for example1 if the stud gear had #if teeth1 the tooth meshing with the idler gear would be marked with chalk1 the gears disengaged1 and the spindle turned until the chalked tooth had made the required part of a revolution1 which could be determined by counting the teeth4 ,when this method is used1 the number of teeth in the stud gear must be evenly divisible by two if a double thread is being cut1 or by three for a triple thread1 etc4 ,if the stud is not geared to the spindle so that each makes the same number of revolutions1 the ratio of the gearing must be considered4 ,illustration3 ,fig4 #ab4 ,views illustrating how a ,double ,square ,thread is ,cut ,setting ,tool ,when ,cutting ,multiple ,threads4--,another method1 which can sometimes be used for setting the tool after cutting the first groove of a multiple thread1 is to disengage the lock-nuts from the lead-screw 7while the spindle is stationary7 and move the carriage back whatever distance is required to locate the tool in the proper position for taking the second cut4 ,evidently this distance must not only locate the tool in the right place1 but be such that the lock-nuts can be re-engaged with the lead-screw4 ,beginning with a simple illustration1 suppose a double thread is being cut having a lead of #a inch4 ,after the first thread groove is cut1 the tool can be set in a central position for taking the second cut1 by simply moving the carriage back #a_/b inch 7one-half the lead71 or #a_/b inch plus the lead or any multiple of the lead4 ,if the length of the threaded part were #e inches1 the tool would be moved back far enough to clear the end of the work1 or say #a_/b #e #e-a_/b inches4 ,in order to disengage the lock-nuts and re-engage them after moving the carriage #e-a_/b inches 7or any distance equal1 in this case1 to one-half plus a whole number71 the lead-screw must have an even number of threads per inch4 ,assume that a double thread is being cut having #a-a_/d single threads per inch4 ,the lead then would equal #a _/ #a-a_/d #j4h inch1 and if the carriage is moved back #j4h _/ #b #j4d inch1 the tool will be properly located for the second cut2 but the lock-nuts could not be re-engaged unless the lead-screw had ten threads per inch1 which is finer than the pitch found on the lead-screws of ordinary engine lathes4 ,however1 if the movement were #j4d #j4h x #b #b inches1 the lock-nuts could be re-engaged regardless of the number of threads per inch on the lead-screw4 ,the rule then1 is as follows3 ,divide the lead of the thread by #b for a double thread1 #c for a triple thread1 #d for a quadruple thread1 etc41 thus obtaining the pitch2 then add the pitch to any multiple of the lead1 which will give a movement1 in inches1 that will enable the lock-nuts to be re-engaged with the lead-screw4 ,whenever the number obtained by this rule is a whole number1 obviously1 the movement can be obtained with a lead-screw of any pitch4 ,if the number is fractional1 the number of threads per inch on the lead-screw must be divisible by the denominator of the fraction4 ,to illustrate the application of the foregoing rule1 suppose a quadruple thread is to be cut having #a-a_/b single threads per inch 7which would be the number the lathe would be geared to cut74 ,then the lead of the thread #a _/ #a-a_/b #j4ffff inch and the pitch #j4ffff _/ #d #j4afff inch2 adding the pitch to twice the lead we have #j4afff #b x #j4ffff #a4dii inch4 ,hence1 if the carriage is moved #a-a_/b inch 7which will require a lead-screw having an even number of threads per inch71 the tool will be located accurately enough for practical purposes4 ,when the tool is set in this way1 if it does not clear the end of the part being threaded1 the lathe can be turned backward to place the tool in the proper position4 ,illustration3 ,fig4 #ac4 ,indexing ,faceplate used for ,multiple ,thread ,cutting ,the foregoing rule1 as applied to triple threads or those of a higher number1 does not always give the only distance that the carriage can be moved4 ,to illustrate1 in the preceding example the carriage movement could be equal to #j4dii1 or what is practically one-half inch1 instead of #a-a_/b inch1 and the tool would be properly located4 ,the rule1 however1 has the merit of simplicity and can be used in most cases4 ,special faceplates are sometimes used for multiple thread cutting1 that enable work to be easily and accurately indexed4 ,one of these is illustrated in ,fig4 #ac2 it consists of two parts ,a and ,b1 part ,a being free to rotate in relation to ,b when bolts ,c are loosened4 ,the driving pin for the lathe dog is attached to plate ,a4 ,when one groove of a multiple thread is finished1 bolts ,c are loosened and plate ,a is turned around an amount corresponding to the type of thread being cut4 ,the periphery of plate ,a is graduated in degrees1 as shown1 and for a double thread it would be turned one-half revolution or #ahj degrees1 for a triple thread1 #abj degrees1 etc4 ,this is a very good arrangement where multiple thread cutting is done frequently4 ,illustration3 ,fig4 #ad4 ,correct and ,incorrect ,positions of ,tool for ,taper ,thread ,cutting ,taper ,threading4--,when a taper thread is to be cut1 the tool should be set square with axis a--a as at ,a1 ,fig4 #ad1 and not by the tapering surface as at ,b4 ,if there is a cylindrical part1 the tool can be set as indicated by the dotted lines4 ,all taper threads should be cut by the use of taper attachments4 ,if the tailstock is set over to get the required taper1 and an ordinary bent-tail dog is used for driving1 the curve of the thread will not be true1 or in other words the thread will not advance at a uniform rate2 this is referred to by machinists as a drunken thread4 ,this error in the thread is due to the angularity between the driving dog and the faceplate1 which causes the work to be rotated at a varying velocity4 ,the pitch of a taper thread that is cut with the tailstock set over will also be slightly finer than the pitch for which the lathe is geared4 ,the amount of these errors depends upon the angle of the taper and the distance that the center must be offset4 ,internal ,threading4--,internal threading1 or cutting threads in holes1 is an operation performed on work held in the chuck or on a faceplate1 as for boring4 ,the tool used is similar to a boring tool except that the working end is shaped to conform to the thread to be cut4 ,the method of procedure1 when cutting an internal thread1 is similar to that for outside work1 as far as handling the lathe is concerned4 ,the hole to be threaded is first bored to the root diameter ,d1 ,fig4 #ae1 of the screw that is to fit into it4 ,the tool-point 7of a tool for a ,u4 ,s4 standard or ,v-thread7 is then set square by holding a gage ,g against the true side of the work and adjusting the point to fit the notch in the gage as shown4 ,the view to the right shows the tool taking the first cut4 ,illustration3 ,fig4 #ae4 ,method of setting and using ,inside ,thread ,tool ,very often the size of a threaded hole can be tested by using as a gage the threaded part that is to fit into it4 ,when making such a test1 the tool is1 of course1 moved back out of the way4 ,it is rather difficult to cut an accurate thread in a small hole1 especially when the hole is quite deep1 owing to the flexibility of the tool2 for this reason threads are sometimes cut slightly under size with the tool1 after which a tap with its shank end held straight by the tailstock center is run through the hole4 ,in such a case1 the tap should be calipered and the thread made just small enough with the tool to give the tap a light cut4 ,small square-threaded holes are often finished in this way1 and if a number of pieces are to be threaded1 the use of a tap makes the holes uniform in size4 ,stop for ,thread ,tools4--,when cutting a thread1 it is rather difficult to feed in the tool just the right amount for each successive cut1 because the tool is moved in before it feeds up to the work4 ,a stop is sometimes used for threading which overcomes this difficulty4 ,this stop consists of a screw ,s1 ,fig4 #af1 which enters the tool slide and passes through a block ,b clamped in front of the slide4 ,the hole in the block through which the stop-screw passes is not threaded1 but is large enough to permit the screw to move freely4 ,when cutting a thread1 the tool is set for the first cut and the screw is adjusted until the head is against the fixed block4 ,after taking the first cut1 the stop-screw is backed out1 say one-half revolution1 which allows the tool to be fed in far enough for a second cut4 ,if this cut is about right for depth1 the screw is again turned about one-half revolution for the next cut and this is continued for each successive cut until the thread is finished4 ,by using a stop of this kind1 there is no danger of feeding the tool in too far as is often done when the tool is set by guess4 ,if this form of stop is used for internal threading1 the screw1 instead of passing through the fixed block1 is placed in the slide so that the end or head will come against the stop ,b4 ,this change is made because the tool is fed outward when cutting an internal thread4 ,illustration3 ,fig4 #af4 ,cross-slide equipped with ,stop for ,regulating ,depth of ,cut when ,threading ,the ,acme ,standard ,thread4--,the ,acme thread is often used1 at the present time1 in place of a square thread4 ,the angle between the sides of the ,acme thread is #bi degrees 7see ,fig4 #ba7 and the depth is made equal to one-half the pitch plus #j4jaj inch to provide clearance and insure a bearing upon the sides4 ,the thread tool is ordinarily ground to fit a gage having notches representing different pitches4 ,an improved form of ,acme thread gage is shown in ,fig4 #ag4 ,the tool point is first ground to the correct angle by fitting it to the #bi-;degree notch in the end of the gage1 as at ,a4 ,the end is then ground to the proper width for the pitch to be cut1 by testing it1 as at ,b4 ,the numbers opposite the shallow notches for gaging the width represent the number of threads per inch4 ,with this particular gage1 the tool can be set square by placing edge ,d against the turned surface to be threaded1 and adjusting the tool until the end is in line with the gage1 as at ,c4 ,by placing the tool in this position1 the angle between the side and the end can also be tested4 ,illustration3 ,fig4 #ag4 ,gage for grinding and setting ,acme ,thread ,tools ,in case it should be necessary to measure the end width of an ,acme thread tool1 for a pitch not on the regular gage1 this can be done by using a vernier gear-tooth caliper1 as indicated in ,fig4 #ah4 ,if we assume that the caliper jaws bear on the sides of the tool at a distance ,a from the top1 equal to #a_/d inch1 then the width of the tool point equals the caliper reading 7as shown by the horizontal scale7 minus #j4abic inch4 ,for example1 if the caliper reading was #j4cae inch1 the width at the point would equal #j4cae - #j4abic #j4aheg inch1 assuming that the sides were ground to the standard angle of #bi degrees4 ,the constant to be subtracted from the caliper reading equals #b ,a tan #ad deg4 #cj' or1 in this case1 #b x #j4be x #j4behf #j4abic4 ,illustration3 ,fig4 #ah4 ,measuring ,width of ,acme ,thread ,tool with ,vernier ,gear-tooth ,caliper ,the ,whitworth ,thread4--,the ,whitworth 7or ,british ,standard ,whitworth7 thread1 which is used principally in ,great ,britain1 has an included angle of #ee degrees1 and the threads are rounded at the top and at the root1 as shown in ,fig4 #bc4 ,the shape of the tool used for cutting this thread is also shown in this illustration4 ,the end is rounded to form the fillet at the root of the thread1 and the round corners on the sides give the top of the thread the required curvature4 ,every pitch requires a different tool1 and the cutting end is given the curved form by milling or hobbing4 ,the hob used for this purpose is accurately threaded to correspond with the pitch for which the tool is required1 and then it is fluted to form cutting edges1 and is hardened4 ,the hob is then used like a milling cutter for forming the end of the thread tool4 ,the tool is sharpened by grinding on the top4 ,the method of cutting a ,whitworth thread is1 of course1 similar to that followed for a ,u4 ,s4 standard or ,v-thread1 in that the tool is set square with the unthreaded blank and at the same height as the lathe centers1 in order to secure a thread of the proper form4 ,care should be taken to turn the blank to the right diameter so that the top of the thread will be fully rounded when the screw is the required size4 ,illustration3 ,fig4 #ai4 ,united ,states ,standard ,thread ,illustration3 ,fig4 #bj4 ,standard ,sharp ,v-thread ,illustration3 ,fig4 #ba4 ,acme ,standard ,thread ,illustration3 ,fig4 #bb4 ,square ,thread ,illustration3 ,fig4 #bc4 ,whitworth ,standard ,thread ,illustration3 ,fig4 #bd4 ,standard ,worm ,thread ,worm ,threads4--,the standard worm thread has an angle of #bi degrees between the sides1 the same as an ,acme thread1 but the depth of a worm thread and the width of the flat at the top and bottom differ from the ,acme standard1 as will be seen by comparing ,figs4 #ba and #bd4 ,the whole depth of the thread equals the linear pitch multiplied by #j4fhff1 and the width of the thread tool at the end equals the linear pitch multiplied by #j4ca4 ,gages notched for threads of different pitch are ordinarily used when grinding worm thread tools4 ,when it is necessary to cut multiple-threaded worms of large lead in an ordinary lathe1 difficulty is sometimes experienced because the lead-screw must be geared to run much faster than the spindle1 thus imposing excessive strains on the gearing4 ,this difficulty is sometimes overcome by mounting a belt pulley on the lead-screw1 beside the change gear1 and connecting it to the countershaft by a belt2 the spindle is then driven through the change gearing from the lead-screw1 instead of vice versa4 ,coarse ,threading ,attachment4--,to avoid the difficulties connected with cutting threads of large lead1 some lathes are equipped with a coarse screw-cutting attachment4 ,the arrangement of this attachment1 as made by the ,bradford ,machine ,tool ,co41 is as follows3 ,on the usual reversing shaft1 and inside of the headstock1 there is a sliding double gear1 so arranged as to be engaged with either the usual gear on the spindle1 or with a small pinion at the end of the cone4 ,the gears are so proportioned that the ratio of the two engagements is as #aj to #a2 that is1 when engaged with the cone gear 7the back-gears being thrown in7 the mating gear will make ten revolutions to one of the spindle1 so that when the lathe is ordinarily geared to cut one thread per inch1 it will1 when driven by the cone pinion1 cut one thread in ten inches4 ,this construction dispenses with the extra strain on the reverse gears due to moving the carriage at the rapid rate that would be necessary for such a large lead1 when not using an attachment4 ,these attachments are not only extensively used for the cutting of coarse screws but for cutting oil grooves on cylindrical parts4 ,when cutting a thread of large lead or steep pitch1 the top of the thread tool should be ground so that it is at right angles to the thread2 then the thread groove will be cut to the same width as the tool4 ,testing the ,size of a ,thread4--,when the thread tool has been fed in far enough to form a complete thread1 the screw is then tested for size4 ,if we assume that a bolt is being threaded for a standard nut1 it would be removed from the lathe and the test made by screwing a nut on the end4 ,if the thread were too large1 the nut might screw on very tightly or not at all2 in either case1 the work would again be placed in the lathe and a light cut taken over it to reduce the thread to the proper size4 ,when replacing a threaded part between the centers1 it should be put back in the original position1 that is1 with the tail of the driving dog in the same slot of the faceplate it previously occupied4 ,illustration3 ,fig4 #be4 ,testing ,diameter of ,thread with ,calipers and ,micrometer ,as it is difficult to tell just when a thread is cut to the exact size1 special thread calipers having wedge-shaped ends are sometimes used for measuring the diameter of a ,v-thread or a ,u4 ,s4 standard thread1 at the bottom of the grooves or the root diameter1 as shown at ,a in ,fig4 #be4 ,these calipers can be set from a tap corresponding to the size of the thread being cut1 or from a previously threaded piece of the right size4 ,the ,thread ,micrometer4--,another form of caliper for testing threads is shown at ,b4 ,this is one of the micrometer type and is intended for very accurate work4 ,the spindle of this micrometer has a conical end and the anvil is ,v-shaped1 and these ends bear on the sides of the thread or the surfaces which form the bearing when the screw is inserted in a nut or threaded hole4 ,the cone-shaped point is slightly rounded so that it will not bear in the bottom of the thread4 ,there is also sufficient clearance at the bottom of the ,v-shaped anvil to prevent it from bearing on top of the thread4 ,the diameter as indicated by this micrometer is the pitch diameter of the thread and is equal to the outside diameter minus the depth of one thread4 ,this depth may be determined as follows3 ,depth of a ,v-thread #j4hff _/ ,no4 of threads per inch2 ,depth of a ,u4 ,s4 standard thread #j4fdie _/ ,no4 of threads per inch2 ,depth of ,whitworth thread #j4fdjc _/ ,no4 of threads per inch4 ,the movable point measures all pitches1 but the fixed anvil is limited in its capacity1 for if made large enough to measure a thread of1 say1 #a_/d-;inch pitch1 it would be too wide at the top to measure a thread of #a_/bd-;inch pitch1 hence each caliper is limited in the range of threads that the anvil can measure4 ,when measuring the angle diameter of a thread1 the micrometer should be passed back and forth across the thread1 in order to make sure that the largest dimension or the actual diameter is being measured4 ,if the micrometer is placed over what seems to be the center of the screw and the reading is taken by simply adjusting in the anvil or point against the thread1 without moving the micrometer back and forth across it1 an incorrect reading may be obtained4 ,if standard threaded reference gages are available1 the size of the thread being cut can be tested by comparing it with the gage4 ,micrometers having small spherical measuring ends 7see sketch ,a1 ,fig4 #bf7 are sometimes used for this purpose4 ,the ball points are small enough to bear against the sides of the thread and the diameter1 as compared with the reference gage1 can be determined with great accuracy4 ,illustration3 ,fig4 #bf4 7,a7 ,testing ,size of ,thread with ,ball-point ,micrometer4 7,b7 ,testing ,size of ,v-thread by the ,three-wire ,system4 7,c7 ,testing the ,size of a ,u4 ,s4 ,standard ,thread ,three-wire ,system of ,measuring ,threads4--,a method of measuring threads by using an ordinary micrometer and three wires of equal diameter is illustrated at ,b and ,c1 ,fig4 #bf4 ,two wires are placed between the threads on one side and one on the opposite side of the screw4 ,the dimension ,m over the wires is then measured with an ordinary micrometer4 ,when the thread is cut to a standard size1 the dimension ,m for different threads is as follows3 ,for a ,u4 ,s4 standard thread3 m d - #a4eaeep #cw ,for a sharp ,v-thread3 m d - #a4gcbp #cw ,for a ,whitworth standard thread3 m d - #a4fjjhp #c4afegw ,in these formulas1 d standard outside diameter of screw2 m measurement over wires2 w diameter of wires2 p pitch of thread #a _/ number of threads per inch4 ,to illustrate the use of the formula for the ,u4 ,s4 standard thread1 let us assume that a screw having #f threads per inch 7#a_/f-;inch pitch7 is to be cut to a diameter of #a-a_/b inch1 and that wires #j4adj inch diameter are to be used in conjunction with a micrometer for measurement4 ,then the micrometer reading m should be #a-a_/b - #a4eaee x #a_/f #c x #j4adj #a4ffgd inch ,if the micrometer reading were #a4fgj inch1 it would indicate that the pitch diameter of the screw was too large1 the error being equal to difference between #a4ffg and the actual reading4 ,illustration3 ,fig4 #bg4 ,rivett-,dock ,circular ,threading ,tool in ,working ,position ,rivett-,dock ,threading ,tool4--,a special form of thread tool1 which overcomes a number of disadvantages common to an ordinary single-point thread tool1 is shown in ,fig4 #bg4 ,this tool has a circular-shaped cutter ,c1 having ten teeth around its circumference1 which1 beginning with tooth ,no4 #a1 gradually increase in height1 cutter ,no4 #b being higher than ,no4 #a1 etc4 ,this cutter is mounted on a slide ,s1 that is fitted to the frame ,f1 and can be moved in or out by lever ,l4 ,the hub of this lever has an eccentric stud which moves slide ,s and locks it when in the forward or cutting position4 ,the action of the lever in moving the slide engages the cutter with pawl ,p1 thus rotating the cutter one tooth at a time and presenting a different tooth to the work for each movement of the lever4 ,when the slide is moved forward1 the heel or underside of the tooth which is in the working position rests on a stop that takes the thrust of the cut4 ,when the tool is in use1 it is mounted on the tool-block of the lathe as shown in the illustration4 ,the cutter is set for height by placing a tooth in the working position and setting the top level with the lathe center4 ,the cutter is also set square with the work by using an ordinary square1 and it is tilted slightly from the vertical to correspond with the angle of the thread to be cut1 by adjusting frame ,f4 ,at first a light cut is taken with lever ,l moved forward and tooth ,no4 #a on the stop4 ,after this cut is completed1 the lever is reversed which rotates the cutter one tooth1 and the return movement places tooth ,no4 #b in the working position4 ,this operation is repeated until the tenth tooth finishes the thread4 ,it is often necessary1 when using a single-point thread tool1 to re-sharpen it before taking the finishing cut1 but with a circular tool this is not necessary1 for by using the different teeth successively1 the last tooth1 which only takes finishing cuts1 is kept in good condition4 ,cutting ,screws to ,compensate for ,shrinkage4--,some tool steels are liable to shrink more or less when they are hardened2 consequently if a very accurate hardened screw is required1 it is sometimes cut so that the pitch is slightly greater than standard1 to compensate for the shrinkage due to the hardening operation4 ,as the amount of contraction incident to hardening is very little1 it is not practicable to use change gears that will give the exact pitch required4 ,a well-known method of obtaining this increase of pitch is by the use of a taper attachment4 ,for example1 suppose a tap having #h threads per inch is to be threaded1 and1 owing to the contraction of the steel1 the pitch must be #j4abejb inch instead of #j4abe inch4 ,the lathe is geared to cut #h threads per inch or #j4abe inch pitch1 and then the taper attachment is set to an angle a1 ,fig4 #bh1 the cosine of which equals #j4abe_/j4abejb2 that is1 the cosine of angle a equals the pitch required after hardening1 divided by the pitch necessary to compensate for shrinkage4 ,the angle is then found by referring to a table of cosines4 ,the tap blank is also set to the same angle a by adjusting the tailstock center1 thus locating the axis of the work parallel with the slide of the taper attachment4 ,when the carriage moves a distance x1 the tool point will have moved a greater distance y along the work1 the difference between x and y depending upon angle a2 hence the tool will cut a thread of slightly greater pitch than the lathe is geared to cut4 ,to illustrate by using the preceding example1 cosine of angle a #j4abe_/j4abejb #j4iiihd4 ,by referring to a table of cosines1 we find that #j4iiihd is the cosine of #a degree1 approximately2 hence1 the taper attachment slide and the work should be set to this angle4 7,the angle a in ,fig4 #bh has been exaggerated in order to more clearly illustrate the principle47 ,illustration3 ,fig4 #bh4 ,diagram ,illustrating ,method of ,cutting a ,thread to ,compensate for the ,error in ,pitch due to ,shrinkage in ,hardening ,as is well known1 it is objectionable to cut a thread with the tailstock center offset1 because the work is not rotated at a uniform velocity1 owing to the fact that the driving dog is at an angle with the faceplate4 ,for a small angle such as #a degree1 however1 the error resulting from this cause would be very small4 ,if a thread having a pitch slightly less than standard is needed to fit a threaded part which has contracted in hardening1 the taper attachment can also be used provided the lathe is equipped with special gears to cut a little less than the required pitch4 ,suppose a screw having a pitch of #j4aih inch is required to fit the thread of a nut the pitch of which has been reduced from #j4bjj inch to #j4aih inch4 ,if gears having #hc and #hd teeth are available1 these can be inserted in a compound train1 so as to reduce the #j4bjj inch pitch that would be obtained with the regular gearing1 to #hc_/hd of #j4bjj or #j4aigfb inch4 ,this pitch1 which is less than the #j4aih inch pitch required1 is then increased by using the taper attachment as previously described4 7,this method was described by ,mr4 ,g4 ,h4 ,gardner in ,,machinery1 ,february1 #aiad47 ,calculating ,change ,gears for ,thread ,cutting4--,as previously mentioned1 the change gears for cutting threads of various pitches are shown by a table or index plate attached to the lathe4 ,the proper gears to be used can be calculated1 but the use of the table saves time and tends to avoid mistakes4 ,every machinist1 however1 should know how to determine the size of gears used for cutting any number of threads to the inch4 ,before referring to any rules1 let us first consider why a lathe cuts a certain number of threads to the inch and how this number is changed by the use of different gears4 ,as the carriage ,c and the tool are moved by the lead-screw ,s 7see ,fig4 #b71 which is geared to the spindle1 the number of threads to the inch that are cut depends1 in every case1 upon the number of turns the work makes while the lead-screw is moving the carriage one inch4 ,if the lead-screw has six threads per inch1 it will make six revolutions while the carriage and the thread tool travel one inch along the piece to be threaded4 ,now if the change gears a and c 7see also sketch ,a1 ,fig4 #bi7 are so proportioned that the spindle makes the same number of revolutions as the lead-screw1 in a given time1 it is evident that the tool will cut six threads per inch4 ,if the spindle revolved twice as fast as the lead-screw1 it would make twelve turns while the tool moved one inch1 and1 consequently1 twelve threads per inch would be cut2 but to get this difference in speeds it is necessary to use a combination of gearing that will cause the lead-screw to revolve once while the lathe spindle and work make two revolutions4 ,illustration3 ,fig4 #bi4 7,a7 ,lathe with ,simple ,gearing for ,thread ,cutting4 7,b7 ,compound ,geared ,lathe ,suppose that nine threads to the inch are to be cut and the lead-screw has six threads per inch4 ,in this case the work must make nine revolutions while the lead-screw makes six and causes the carriage and thread tool to move one inch1 or in other words1 one revolution of the lead-screw corresponds to one and one-half revolution of the spindle2 therefore1 if the lead-screw gear c has #cf teeth1 the gear a on the spindle stud should have #bd teeth4 ,the spindle will then revolve one and one-half times faster than the lead-screw1 provided the stud rotates at the same rate of speed as the main lathe spindle4 ,the number of teeth in the change gears that is required for a certain pitch can be found by multiplying the number of threads per inch of the lead-screw1 and the number of threads per inch to be cut1 by the same trial multiplier4 ,the formula which expresses the relation between threads per inch of lead-screw1 threads per inch to be cut1 and the number of teeth in the change gears1 is as follows3 threads per inch of lead-screw teeth in gear on spindle stud ------------------------------ ----------------------------- threads per inch to be cut teeth in gear on lead-screw ,applying this to the example given1 we have #f_/i #bd_/cf4 ,the values of #cf and #bd are obtained by multiplying #f and #i1 respectively1 by #d1 which1 of course1 does not change the proportion4 ,any other number could be used as a multiplier1 and if gears having #bd and #cf teeth were not available1 this might be necessary4 ,for example1 if there were no gears of this size1 some other multiplier as #e or #f might be used4 ,suppose the number of teeth in the change gears supplied with the lathe are #bd1 #bh1 #cb1 #cf1 etc41 increasing by four teeth up to #ajj1 and assume that the lead-screw has #f threads per inch and that #aj threads per inch are to be cut4 ,then1 #f #f x #d #bd -- ------ -- #aj #aj x #d #dj ,by multiplying both numerator and denominator by #d1 we obtain two available gears having #bd and #dj teeth1 respectively4 ,the #bd-tooth gear goes on the spindle stud and1 the #dj-tooth gear on the lead-screw4 ,the number of teeth in the intermediate or idler gear b1 which connects the stud and lead-screw gears1 is not considered as it does not affect the ratios between gears a and c1 but is used simply to transmit motion from one gear to the other4 ,we have assumed in the foregoing that the spindle stud 7on which gear a is mounted7 and the main spindle of the lathe are geared in the ratio of one to one and make the same number of revolutions4 ,in some lathes1 however1 these two members do not rotate at the same speed1 so that if equal gears were placed on the lead-screw and spindle stud1 the spindle would not make the same number of revolutions as the lead-screw4 ,in that case if the actual number of threads per inch in the lead-screw were used when calculating the change gears1 the result would be incorrect2 hence1 to avoid mistakes1 the following general rule should be used as it gives the correct result1 regardless of the ratios of the gears which connect the spindle and spindle stud3 ,rule4--,first find the number of threads per inch that is cut when gears of the same size are placed on the lead-screw and spindle1 either by actual trial or by referring to the index plate4 ,then place this number as the numerator of a fraction and the number of threads per inch to be cut1 as the denominator2 multiply both numerator and denominator by some trial number1 until numbers are obtained which correspond to numbers of teeth in gears that are available4 ,the product of the trial number and the numerator 7or lathe screw constant7 represents the gear a for the spindle stud1 and the product of the trial number and the denominator1 the gear for the lead-screw4 ,lathes with ,compound ,gearing4--,when gearing is arranged as shown at ,a1 ,fig4 #bi1 it is referred to as simple gearing1 but sometimes it is necessary to introduce two gears between the stud and screw as at ,b1 which is termed compound gearing4 ,the method of figuring compound gearing is practically the same as that for simple gearing4 ,to find the change gears used in compound gearing1 place the screw constant obtained by the foregoing rule1 as the numerator1 and the number of threads per inch to be cut as the denominator of a fraction2 resolve both numerator and denominator into two factors each1 and multiply each pair of factors by the same number1 until values are obtained representing numbers of teeth in available change gears4 7,one factor in the numerator and one in the denominator make a pair of factors47 ,suppose the lathe cuts #f threads per inch when gears of equal size are used1 and that the number of teeth in the gears available are #cj1 #ce1 #dj and so on1 increasing by #e up to #ajj4 ,if #bd threads per inch are to be cut1 the screw constant #f is placed in the numerator and #bd in the denominator4 ,the numerator and denominator are then divided into factors and each pair of factors is multiplied by the same number to find the gears1 thus3 #f #b x #c 7#b x #bj7 x 7#c x #aj7 #dj x #cj -- ----- ------------------- ------- #bd #d x #f 7#d x #bj7 x 7#f x #aj7 #hj x #fj ,the last four numbers indicate the gears which should be used4 ,the upper two having #dj and #cj teeth are the driving gears and the lower two having #hj and #fj teeth are the driven gears4 ,the driving gears are gear a on the spindle stud and gear c on the intermediate stud1 meshing with the lead-screw gear1 and the driven gears are gears b and d4 ,it makes no difference which of the driving gears is placed on the spindle stud1 or which of the driven is placed on the lead-screw4 ,fractional ,threads4--,sometimes the lead of a thread is given as a fraction of an inch instead of stating the number of threads per inch4 ,for example1 a thread may be required to be cut1 having #c_/h-;inch lead4 ,the expression #c_/h-;inch lead should first be transformed to number of threads per inch4 ,the number of threads per inch 7the thread being single7 equals3 #a #c #h --- #a _/ - - #b-b_/c #c_/h #h #c ,to find the change gears to cut #b-b_/c threads per inch in a lathe having a screw constant of #h and change gears varying from #bd to #ajj teeth1 increasing by #d1 proceed as follows3 #h #b x #d 7#b x #cf7 x 7#d x #bd7 #gb x #if ----- --------- ----------------------- ------- #b-b_/c #a x #b-b_/c 7#a x #cf7 x 7#b-b_/c x #bd7 #cf x #fd ,as another illustration1 suppose we are to cut #a-c_/d thread per inch on a lathe having a screw constant of #h1 and that the gears have #bd1 #bh1 #cb1 #cf1 #dj teeth1 etc41 increasing by four up to one hundred4 ,following the rule3 #h #b x #d 7#b x #cf7 x 7#d x #af7 #gb x #fd ----- --------- ----------------------- ------- #a-c_/d #a x #a-c_/d 7#a x #cf7 x 7#a-c_/d x #af7 #cf x #bh ,the gears having #gb and #fd teeth are the driving gears1 and those with #cf and #bh teeth are the driven gears4 ,change ,gears for ,metric ,pitches4--,when screws are cut in accordance with the metric system1 it is the usual practice to give the lead of the thread in millimeters1 instead of the number of threads per unit of measurement4 ,to find the change gears for cutting metric threads1 when using a lathe having an ,english lead-screw1 first determine the number of threads per inch corresponding to the given lead in millimeters4 ,suppose a thread of #c millimeters lead is to be cut in a lathe having an ,english lead-screw and a screw constant of #f4 ,as there are #be4d millimeters per inch1 the number of threads per inch will equal #be4d _/ #c4 ,place the screw constant as the numerator1 and the number of threads per inch to be cut as the denominator3 #f #be4d #f x #c ------- #f _/ ---- ----- #be4d #c #be4d ---- #c ,the numerator and denominator of this fractional expression of the change-gear ratio are next multiplied by some trial number to determine the size of the gears4 ,the first whole number by which #be4d can be multiplied so as to get a whole number as the result is #e4 ,thus1 #be4d x #e #abg2 hence1 one gear having #abg teeth is always used when cutting metric threads with an ,english lead-screw4 ,the other gear required in this case has #ij teeth4 ,thus3 #f x #c x #e #ij --------- --- #be4d x #e #abg ,therefore1 the following rule can be used to find the change gears for cutting metric pitches with an ,english lead-screw3 ,rule4--,place the lathe screw constant multiplied by the lead of the required thread in millimeters multiplied by #e1 as the numerator of the fraction1 and #abg as the denominator4 ,the product of the numbers in the numerator equals the number of teeth for the spindle-stud gear1 and #abg is the number of teeth for the lead-screw gear4 ,if the lathe has a metric pitch lead-screw1 and a screw having a given number of threads per inch is to be cut1 first find the metric screw constant of the lathe or the lead of thread in millimeters that would be cut with change gears of equal size on the lead-screw and spindle stud2 then the method of determining the change gears is simply the reverse of the one already explained for cutting a metric thread with an ,english lead-screw4 ,rule4--,to find the change gears for cutting ,english threads with a metric lead-screw1 place #abg in the numerator and the threads per inch to be cut1 multiplied by the metric screw constant multiplied by #e1 in the denominator2 #abg is the number of teeth on the spindle-stud gear and the product of the numbers in the denominator equals the number of teeth in the lead-screw gear4 ,quick ,change-gear ,type of ,lathe4--,a type of lathe that is much used at the present time is shown in ,fig4 #cj4 ,this is known as the quick change-gear type1 because it has a system of gearing which makes it unnecessary to remove the change gears and replace them with different sizes for cutting threads of various pitches4 ,changes of feed are also obtained by the same mechanism1 but the feeding movement is transmitted to the carriage by the rod ,r1 whereas the screw ,s#a is used for screw cutting4 ,as previously explained1 the idea of using the screw exclusively for threading is to prevent it from being worn excessively1 as it would be if continually used in place of rod ,r1 for feeding the carriage when turning4 ,illustration3 ,fig4 #cj4 ,lathe having ,quick ,change-gear ,mechanism ,illustration3 ,fig4 #ca4 ,end and ,side ,views of ,quick ,change-gear ,mechanism ,the general construction of this quick change gear mechanism and the way the changes are made for cutting threads of different pitch1 will be explained in connection with ,figs4 #cj1 #ca and #cb1 which are marked with the same reference letters for corresponding parts4 ,referring to ,fig4 #cj1 the movement is transmitted from gear s on the spindle stud through idler gear ,i1 which can be moved sidewise to mesh with either of the three gears a1 b or c1 ,fig4 #ca4 ,this cone of three gears engages gears d1 e and f1 any one of which can be locked with shaft ,t 7,fig4 #cb7 by changing the position of knob ,k4 ,on shaft ,t there is a gear ,s which can be moved along the shaft by hand lever ,l and1 owing to the spline or key t1 both the sliding gear and shaft rotate together4 ,shaft ,t1 carrying gears d1 e and f and the sliding gear ,s1 is mounted in a yoke ,y1 which can be turned about shaft ,n1 thus making it possible to lower sliding gear ,s into mesh with any one of a cone of eight gears ,c1 ,fig4 #ca4 ,the shaft on which the eight gears are mounted has at the end a small gear m meshing with gear n on the feed-rod1 and the latter1 in turn1 drives the lead-screw1 unless gear o is shifted to the right out of engagement1 which is its position except when cutting threads4 ,illustration3 ,fig4 #cb4 ,sectional ,views of ,quick ,change-gear ,mechanism ,with this mechanism1 eight changes for different threads or feeds are obtained by simply placing gear ,s into mesh with the various sized gears in cone ,c4 ,as the speed of shaft ,t depends on which of the three gears d1 e and f are locked to it1 the eight changes are tripled by changing the position of knob ,k1 making twenty-four4 ,now by shifting idler gear ,i1 three speed changes may be obtained for gears a1 b and c1 which rotate together1 so that the twenty-four changes are also tripled1 giving a total of seventy-two variations without removing any gears1 and if a different sized gear s were placed on the spindle stud1 an entirely different range could be obtained1 but such a change would rarely be necessary4 ,as shown in ,fig4 #cj1 there are eight hardened steel buttons ,b1 or one for each gear of the cone ,c1 placed at different heights in the casing4 ,when lever ,l is shifted sidewise to change the position of sliding gear ,s1 it is lowered onto one of these buttons 7which enters a pocket on the under side7 and in this way gear ,s is brought into proper mesh with any gear of the cone ,c4 ,to shift lever ,l1 the handle is pulled outward against the tension of spring r 7,fig4 #cb71 which disengages latch l and enables the lever to be lifted clear of the button2 yoke ,y is then raised or lowered1 as the case may be1 and lever ,l with the sliding gear is shifted laterally to the required position4 ,illustration3 ,fig4 #cc4 ,index ,plate showing ,position of ,control ,levers for ,cutting ,threads of ,different ,pitch ,the position of lever ,l and knob ,k for cutting threads of different pitches is shown by an index plate or table attached to the lathe and arranged as shown in ,fig4 #cc4 ,the upper section a of this table shows the different numbers of threads to the inch that can be obtained when idler gear ,i is in the position shown by the diagram ,a4 ,section b gives the changes when the idler gear is moved1 as shown at ,b1 and1 similarly1 section c gives the changes for position ,c of the idler4 ,the horizontal row of figures from #a to #h below the word stops represents the eight positions for lever ,l1 which has a plate p 7,fig4 #cj7 just beneath it with corresponding numbers1 and the column to the left shows whether knob ,k should be out1 in a central position1 or in4 ,in order to find what the position of lever ,l and knob ,k should be for cutting any given number of threads to the inch1 find what stop number is directly above the number of threads to be cut1 which will indicate the location of lever ,l1 and also what position should be occupied by knob ,k1 as shown in the column to the left4 ,for example1 suppose the lathe is to be geared for cutting eight threads to the inch4 ,by referring to section a we see that lever ,l should be in position #d and knob ,k in the center1 provided the idler gear ,i were in position ,a1 as it would be ordinarily1 because all standard numbers of threads per inch 7,u4 ,s4 standard7 from #a_/d inch up to and including #d inches in diameter can be cut with the idler gear in that position4 ,as another illustration1 suppose we want to cut twenty-eight threads per inch4 ,this is listed in section c1 which shows that lever ,l must be placed in position #c with knob ,k pushed in and the idler gear shifted to the left as at ,c4 ,the simplicity of this method as compared with the time-consuming operation of removing and changing gears is apparent4 ,the diagram ,d to the right shows an arrangement of gearing for cutting nineteen threads per inch4 ,a #bj-tooth gear is placed on the spindle stud 7in place of the regular one having #af teeth7 and one with #ie teeth on the lead-screw1 thus driving the latter direct as with ordinary change gears4 ,of course it will be understood that the arrangement of a quick change-gear mechanism varies somewhat on lathes of different make4 ,,chapter ,v ,,turret ,,lathe ,,practice ,turret lathes are adapted for turning duplicate parts in quantity4 ,the characteristic feature of a turret lathe is the turret which is mounted upon a carriage and contains the tools which are successively brought into the working position by indexing or rotating the turret4 ,in many instances1 all the tools required can be held in the turret1 although it is often necessary to use other tools1 held on a cross-slide1 for cutting off the finished part1 facing a radial surface1 knurling1 or for some other operation4 ,after a turret lathe is equipped with the tools needed for machining a certain part1 it produces the finished work much more rapidly than would be possible by using an ordinary engine lathe1 principally because each tool is carefully set for turning or boring to whatever size is required and the turret makes it possible to quickly place any tool in the working position4 ,turret lathes also have systems of stops or gages for controlling the travel of the turret carriage and cross-slide1 in order to regulate the depth of a bored hole1 the length of a cylindrical part or its diameter2 hence1 turning machines of this type are much more efficient than ordinary lathes for turning duplicate parts1 unless the quantity is small1 in which case1 the advantage of the turret lathe might be much more than offset by the cost of the special tool equipment and the time required for setting up the machine4 7,see ,selecting ,type of ,turning ,machine47 ,illustration3 ,fig4 #a4 ,bardons ,oliver ,turret ,lathe of ,motor-driven ,geared-head ,type ,general ,description of a ,turret ,lathe4--,the turret lathe shown in ,fig4 #a has a hexagonal shaped turret ,a with a hole in each side in which the tools are held4 ,this turret is mounted on a slide ,b which is carried by a saddle ,c that can be moved along the bed to locate the turret slide with reference to the length of the tools in the turret and the room required for indexing4 ,the turret slide can be moved longitudinally by turning the pilot wheel or turnstile ,d1 or it can be fed by power4 ,ordinarily1 the hand adjustment is used for quickly moving the carriage when the tools are not cutting1 although sometimes the hand feed is preferable to a power feed when the tools are at work1 especially if the cuts are short4 ,after a turret tool has finished its cut1 the turnstile is used to return the slide to the starting point1 and at the end of this backward movement the turret is automatically indexed or turned one-sixth of a revolution1 thus bringing the next tool into the working position4 ,the turret is accurately located in each of its six positions by a lock bolt which engages notches formed in a large index ring at the turret base4 ,a binder lever ,e at the top of the turret stud is used to clamp the turret rigidly to the slide when the tools are cutting4 ,the forward movement of the slide for each position of the turret is controlled by stops at ,f1 which are set to suit the work being turned4 ,when parts are being turned from bar stock1 the latter passes through the hollow spindle of the headstock and extends just far enough beyond the end of the spindle to permit turning one of the parts4 ,the bar is held while the turning tools are at work1 by a chuck of the collet type at ,g4 ,this chuck is opened or closed around the bar by turning handwheel ,h4 ,after a finished part has been cut off by a tool held in cross-slide ,j1 the chuck is released and further movement of wheel ,h causes ratchet feed dog ,k1 and the bar which passes through it1 to be drawn forward4 ,this forward movement is continued until the end of the bar comes against a stop gage held in one of the turret holes1 to insure feeding the bar out just the right amount for turning the next piece4 ,on some turret lathes1 the lever which operates the chuck also controls a power feed for the bar stock1 the latter being pushed through the spindle against the stop4 ,the machine illustrated has a power feed for the cross-slide as well as for the turret4 ,the motion is obtained from the same shaft ,l which actuates the turret slide1 but the feed changes are independent4 ,the cross-slide feed changes are varied by levers ,m and those for the turret by levers ,n4 ,for many turret lathe operations1 such as turning castings1 etc41 a jawed chuck is screwed onto the spindle and the work is held the same as when a chuck is used on an engine lathe4 ,sometimes chucks are used having special jaws for holding castings of irregular shape1 or special work-holding fixtures which are bolted to the faceplate4 ,the small handle at ,o is for moving the cross-slide along the bed when this is necessary in order to feed a tool sidewise4 ,this particular machine is driven by a motor at the rear of the headstock1 connection being made with the spindle through gearing4 ,the necessary speed changes are obtained both by varying the speed of the motor and by shifting gears in the headstock4 ,the motor is controlled by the turnstile ,p and the gears are shifted by the vertical levers shown4 ,while many of the features referred to are common to turret lathes in general1 it will be understood that the details such as the control levers1 arrangement of stops1 etc41 vary on turret lathes of different make4 ,illustration3 ,figs4 #b and #c4 ,diagrams showing ,turret ,lathe ,tool ,equipment for ,machining ,automobile ,hub ,casting ,example of ,turret ,lathe ,work4--,the diagrams ,figs4 #b and #c show a turret lathe operation which is typical in many respects4 ,the part to be turned is a hub casting for an automobile and it is machined in two series of operations4 ,the first series is shown by the plan view1 ,fig4 #b4 ,the casting ,a is held in a three-jaw chuck ,b4 ,tool ,no4 #a on the cross-slide is equipped with two cutters and rough faces the flange and end1 while the inner and outer surfaces of the cylindrical part are rough bored and turned by combination boring and turning tool ,no4 #b4 ,this tool has1 in addition to a regular boring-bar1 a bracket or tool-holder which projects above the work and carries cutters that operate on the top surface4 ,tools ,nos4 #c and #d next come into action1 ,no4 #c finishing the surfaces roughed out by ,no4 #b1 and ,no4 #d finish-facing the flange and end of the hub4 ,the detailed side view of ,tool ,no4 #c 7which is practically the same as ,no4 #b71 shows the arrangement of the cutters ,c and ,d1 one of which turns the cylindrical surface and the other bevels the end of the hub4 ,the hole in the hub is next finished by tool ,no4 #e which is a stepped reamer that machines the bore and counterbore to the required size within very close limits4 ,the surfaces machined by the different tools referred to are indicated by the sectional view ,e of the hub1 which shows by the numbers what tools are used on each surface4 ,for the second series of operations1 the position of the hub is reversed and it is held in a spring or collet type of chuck as shown by the plan view ,fig4 #c4 ,the finished cylindrical end of the hub is inserted in the split collet ,f which is drawn back into the tapering collet ring by rod ,g 7operated by turnstile ,h1 ,fig4 #a7 thus closing the collet tightly around the casting4 ,the first operation is that of facing the side of the flange and end of the hub with tool ,no4 #f on the cross-slide1 which is shown in the working position4 ,a broad cutter ,h is used for facing the flange and finishing the large fillet1 and the end is faced by a smaller cutter ,i4 ,when these tools are withdrawn1 tool ,no4 #g is moved up for rough turning the outside of the cylindrical end 7preparatory to cutting a thread7 and rough boring the hole4 ,these same surfaces are then finished by tool ,no4 #h4 ,the arrangement of tools ,nos4 #g and #h is shown by the detailed view4 ,tool ,j turns the part to be threaded2 tool ,k turns the end beyond the threaded part2 and tool ,l bevels the corner or edge4 ,the reaming tool ,no4 #i is next indexed to the working position for finishing the hole and beveling the outer edge slightly4 ,at the same time1 the form tool ,no4 #aj1 held at the rear of the cross-slide1 is fed up for beveling the flange to an angle of #fj degrees4 ,the final operation is that of threading the end1 which is done with die ,no4 #aa4 ,the boring-bars of tools ,nos4 #b1 #c1 #g and #h are all provided with pilots ,n which enter close fitting bushings held in the spindle1 to steady the bar while taking the cut4 ,this is a common method of supporting turret lathe tools4 ,the feed of the turret for both the first and second series of operations is #a_/bg inch per revolution and the speeds #fj revolutions per minute for the roughing cuts and #ij revolutions per minute for the finishing cuts4 ,the total time for machining one of these castings complete is about #g-a_/b minutes1 which includes the time required for placing the work in the chuck4 ,machining ,flywheels in ,turret ,lathe4--,figs4 #d to #f1 inclusive1 illustrate how a gasoline engine flywheel is finished all over in two cycles of operations4 ,first the flywheel is turned complete on one side1 the hole bored and reamed1 and the outside of the rim finished2 in the second cycle the other side of the flywheel is completed4 ,illustration3 ,fig4 #d4 ,first ,cycle of ,operations in ,finishing ,gasoline ,engine ,flywheels on a ,pond ,turret ,lathe ,during the first operation1 the work is held by the inside of the rim by means of a four-jaw chuck equipped with hard jaws4 ,the side of the rim1 the tapering circumference of the recess1 the web1 and the hub are first rough-turned1 using tools held in the carriage toolpost4 ,the hole is then rough-bored by bar ,c1 which is supported in a bushing in the chuck1 as shown in ,fig4 #d4 ,the outside of the wheel rim is rough-turned at the same time by a cutter held in the extension turret tool-holder ,t 7,fig4 #e71 and the taper fit on the inside of the flywheel is turned by means of cutter ,a 7,fig4 #d7 held in a tool-holder attached to the turret4 ,the outside of the wheel rim is next finish-turned with cutter ,v 7,fig4 #e7 held in an extension turret tool-holder the same as the roughing tool ,t4 ,at the same time1 the bore is finished by a cutter in boring-bar ,d 7,fig4 #d74 ,the side of the rim and the hub of the wheel are also finished at this time by two facing cutters ,h and ,k1 held in tool-holders on the face of the turret4 ,when the finishing cuts on the rim and hub are being taken1 the work is supported by a bushing on the boring-bar which enters the bore of the wheel1 the boring cutter and facing tools being set in such relation to each other that the final boring of the hole is completed before the facing cuts are taken4 ,illustration3 ,fig4 #e4 ,elevation of ,turret and ,tools for ,finishing ,flywheels--,first ,operation ,the web of the wheel is next finish-faced with the facing cutter held in the holder ,e1 and the taper surface on the inside of the rim is finished by the tool ,l1 at the same time4 ,while these last operations are performed1 the work is supported by a bushing on a supporting arbor ,j1 which enters the bore of the wheel4 ,the bore is finally reamed to size by a reamer ,f held in a floating reamer-holder4 ,when the reaming operation is completed1 a clearance groove ,n is cut on the inside of the rim1 using a tool ,g held in the carriage toolpost4 ,the first cycle of operations on the flywheel is now completed4 ,the flywheel is then removed from the chuck1 turned around1 and held in soft jaws for the second cycle of operations1 the jaws fitting the outside of the wheel rim4 7,soft unhardened jaws are used to prevent marring the finished surface of the rim47 ,the operations on this side are very similar to those performed on the other side4 ,first1 the side of the rim1 the inside of the rim1 the web1 and hub are rough-turned1 using tools held in the carriage toolpost4 ,the inside of the rim and the web are then finished by a cutter held in a tool-holder at ,p1 ,fig4 #f1 which is bolted to the face of the turret4 ,the work is supported during this operation by a bushing held on a supporting arbor ,u1 having a pilot which enters a bushing in the chuck4 ,finally1 the rim and hub are finished1 by the facing cutters ,r and ,s1 the work being supported by an arbor1 as before4 ,illustration3 ,fig4 #f4 ,second ,cycle of ,operations on ,flywheel ,these operations illustrate the methods employed in automobile factories1 and other shops where large numbers of engine flywheels1 etc41 must be machined4 ,finishing a ,flywheel at ,one ,setting in ,turret ,lathe4--,the plan view ,a1 ,fig4 #g1 shows an arrangement of tools for finishing a flywheel complete at one setting4 ,the hole for the shaft has to be bored and reamed and the hub faced on both sides4 ,the sides and periphery of the rim also have to be finished and all four corners of the rim rounded4 ,the tools for doing this work consist of boring-bars1 a reamer1 facing heads on the main turret1 a turret toolpost on the slide rest 7carrying1 in this case1 three tools7 and a special supplementary wing rest attached to the front of the carriage at the extreme left4 ,the casting is held by three special hardened jaws b in a universal chuck4 ,these jaws grip the work on the inner side of the rim1 leaving room for a tool to finish the rear face without striking the chuck body or jaws4 ,three rests c are provided between the chuck jaws4 ,the work is pressed against these rests while being tightened in the chuck1 and they serve to locate it so that the arms will run true so far as sidewise movement is concerned4 ,these rests also locate the casting with relation to the stops for the turret and carriage movements4 ,the chuck carries a bushing r of suitable diameter to support the boring-bars in the main turret1 as will be described4 ,in the first operation1 boring-bar m is brought in line with the spindle and is entered in bushing r in the chuck4 ,double-ended cutter n is then fed through the hub of the pulley to true up the cored hole4 ,while boring the hole1 the scale on the front face of the rim and hub is removed by tool j4 ,tool k is then brought into action to rough turn the periphery1 after which tool e1 in the wing rest1 is fed down to clean up the back face of the rim4 ,as soon as the scale is removed1 the hole is bored nearly to size by cutter n#a in bar m#a1 and it is finally finished with reamer q mounted on a floating arbor4 ,the cutters f1 g and h1 in the facing head1 are next brought up to rough face the hub and rim1 and round the corners of the rim on the front side4 ,this operation is all done by broad shaving cuts4 ,the facing head in which the tools are held is provided with a pilot bar t which fits the finished hole in the flywheel hub1 and steadies the head during the operation4 ,the cutters f1 g and h are mounted in holders which may be so adjusted as to bring them to the proper setting for the desired dimensions4 ,this completes the roughing operations4 ,illustration3 ,fig4 #g4 ,turret ,lathe ,tool ,equipment for ,machining ,flywheels ,the periphery of the rim is now finished by cutter l in the turret toolpost which is indexed to the proper position for this operation4 ,the rear face of the rim is finished by the same tool e with which the roughing was done4 ,tool e is then removed and replaced with d which rounds the inner corner of the rim4 ,tool d is also replaced with a third tool for rounding the outer corner of the rear side4 ,for finishing the front faces of the rim and hub and rounding the corners of the rim1 a second facing head1 identical with the first one1 is employed4 ,this is shown in position in the illustration4 ,cutters f#a1 g#a and h#a correspond with the cutters f1 g and h1 previously referred to1 and perform the same operations4 ,the remaining operation of finishing the back of the hub is effected by cutter p4 ,this cutter is removed from the bar1 which is then inserted through the bore2 the cutter is then replaced in its slot and the rear end of the hub is faced by feeding the carriage away from the headstock4 ,this completes the operations1 the flywheel being finished at one setting4 ,finishing a ,webbed ,flywheel in ,two ,settings4--,the plan views ,b and ,c1 ,fig4 #g1 show the arrangement of tools for finishing a webbed flywheel which has to be machined all over4 ,this1 of course1 requires two operations4 ,in the first of these 7see sketch ,b7 the rough casting is chucked on the inside of the rim with regular inside hard chuck jaws b4 ,the cored hole is first rough bored with cutter n attached to the end of boring-bar m1 and guided by the drill support d pivoted to the carriage4 ,next1 the boring-bar m#a is brought into position1 the drill support being swung back out of the way4 ,this bar is steadied by its bearing in bushing r in the chuck4 ,two cutters1 n#a and n#b1 are used to roughly shape the hole to the desired taper1 the small end being finished to within #j4jjb inch of the required diameter4 ,while boring with the bar m#a1 the scale is broken on the web and hub of the casting by the tool k in the turret toolpost4 ,the latter is then shifted to bring the tool j into position for removing the scale on the periphery of the wheel4 ,next1 the hole is reamed with taper reamer q1 the pilot of which is supported by bushing r4 ,the first of the facing heads is now brought into action4 ,this facing head carries a guide t which is steadied in a taper bushing c1 driven into the taper hole of the hub for that purpose4 ,the top cutter f turns the periphery1 cutter g turns the hub and faces the web1 and cutter h faces the rim4 ,a fourth cutter e on the under side of the head faces the hub4 ,this casting is now machined approximately to size4 ,for finishing1 similar cutters1 e#a1 f#a1 g#a and h#a1 in the other facing head are used1 the latter being supported by the taper bushing c in the same way4 ,a very light cut is taken for finishing4 ,tool l in the carriage turret is used to round the outer and inner corners of the rim1 which completes the work on this face of the casting4 ,in the second cycle of operations1 shown at ,c1 the casting is chucked on the outside with the soft jaws b1 which are bored to the exact diameter of the finished rim4 ,the work is further supported and centered by sliding bushing c1 which is tapered to fit the finished hole in the hub1 and has an accurate bearing in bushing r in the chuck4 ,this bushing is provided with a threaded collar for forcing it into the work and withdrawing it4 ,the scale on the web and the inside and face of the rim is first broken with the tool k in the turret toolpost4 ,these surfaces are then roughed off with cutters f1 g and h1 in the facing head4 ,this latter is steadied by a pilot t which enters the hole in the sliding bushing c on which the work is supported4 ,a light cut is next taken with cutters f#a1 g#a and h#a1 in the finishing facing head1 which completes the operation4 ,tools for ,turret ,lathes4--,the operation of a turret lathe after the tools have been properly arranged is not particularly difficult1 but designing and making the tools1 determining what order of operations will give the most efficient and accurate results1 and setting the tools on the machine1 requires both skill and experience4 ,for some classes of work1 especially if of a rather complicated nature1 many of the tools must be specially designed1 although there are certain standard types used on turret lathes which are adapted to general turning operations4 ,some of the principal types are referred to in the following4 ,box-tools4--,tools of this type are used for turning bar stock4 ,there are many different designs1 some of which are shown in ,figs4 #h1 #i and #aj4 ,box-tools are held in the turret and they have back-rests opposite the turning tools1 for supporting the part being turned4 ,the box-tool shown at ,a1 ,fig4 #h1 is for roughing4 ,the cutter a is a piece of high-speed steel beveled on the cutting end to produce a keen edge4 ,it takes a shearing tangent cut on top of the bar and the latter is kept from springing away by means of the adjustable1 hardened tool-steel back-rest b4 ,this tool is considered superior to a hollow mill whenever a fair amount of stock must be removed4 ,if considerable smoothness and accuracy are necessary1 the finishing box-tool shown at ,b should follow the roughing box tool1 but in most cases1 especially if the part is to be threaded by a die1 a finishing cut is unnecessary4 ,illustration3 ,fig4 #h4 ,different ,types of ,box-tools for ,turret ,lathe ,the finishing box-tool ,b is also used to follow a hollow mill if special accuracy or smoothness is desired4 ,this tool is only intended for light finishing cuts1 the allowances varying from #j4jje inch to #j4jae inch in diameter4 ,the cutters are made of square tool steel of commercial size1 and are ground and set to take a scraping end cut4 ,this particular tool has two tool-holders which permit finishing two diameters at once4 ,if a larger number of sizes must be turned1 extra tool-holders can be applied4 ,the single-cutter box-tool shown at ,c is bolted directly to the face of the turret instead of being held by a shank in the turret hole1 and it is adapted for heavy cuts such as are necessary when turning comparatively large bar stock4 ,the tool-holder a swivels on a stud1 thus allowing the cutter to be withdrawn from the work while being returned1 which prevents marring the turned surface4 ,the high-speed steel cutter is ground to take a side cut on the end of the bar4 ,the latter is supported by hardened and ground tool-steel rolls b which revolve on hardened and ground studs4 ,these rolls are mounted on swinging arms which have a screw adjustment for different diameters4 ,they can also be adjusted parallel to the bar1 thus enabling them to be set either in advance of or back of the cutter4 ,the opening in the base allows the stock to pass into the turret when it is not larger than the turret hole4 ,the box-tool shown at ,d is similar to the one just described1 except that it has two or more cutters and roller back-rests1 thus enabling different diameters to be turned simultaneously4 ,the cutters are ground to take a side cut4 ,ordinarily this gives a satisfactory finish1 but if special accuracy and smoothness are desired1 two tools should be used1 one for roughing and one for finishing1 the latter being ground to take a light scraping end cut4 ,the taper-turning box-tool shown at ,e is designed for accurately turning tapers on brass or cast-iron parts1 when there is a small amount of stock to be removed4 ,the taper is obtained by cross motion imparted to the cutter slide as the turret advances4 ,the taper-turning box-tool shown at ,f1 instead of having a single-point cutter1 is provided with a wide cutter a4 ,this tool is designed to turn tapering parts of small or medium diameter1 requiring the use of a support which cannot be provided with a straight forming tool and holder mounted on the cut-off slide4 ,the cutter is backed up by the screws shown1 which also provide adjustment for different tapers within a limited range4 ,the bar is supported by the three back-rests shown1 which also have screw adjustment4 ,examples of ,box-tool ,turning4--,box-tools are not only used for cylindrical and taper turning on the end of a bar1 but for many other operations4 ,figs4 #i and #aj show a number of box-tools of different designs1 with examples of the work for which each is intended4 ,while these tools are designed for some specific part1 they can1 of course1 with slight modifications be adapted to other work4 ,illustration3 ,fig4 #i4 ,box-tools and ,work for which they are ,intended ,a box-tool of the pilot type that is used for finishing1 after the surplus stock has been removed by roughing tools1 is shown at ,a1 ,fig4 #i4 ,the work1 which is the cone for a ball bearing1 is shown at a by the dotted lines and also by the detail view to the right4 ,the pilot b enters the work before either of the cutters begins to operate on its respective surface4 ,the inverted cutter c1 which sizes the flange of the cone1 is held in position by a clamp d1 which is forced down by a collar-head screw4 ,the cutter is further secured against a beveled shoulder at g by the set-screws f1 and it is adjusted forward by the screw e4 ,by loosening the screws f and the collar-head screw1 the cutter may be removed for sharpening4 ,the cutter h is adjusted to cut to the proper diameter1 by the screws l1 after which the clamp k is made level by the screw j4 ,the collar-screw m is then used to secure the tool in place4 ,the cutter is made from drill rod and it is slightly cupped out on the cutting end to give keenness to the cutting edge4 ,the adjusting screw o1 which passes through plate p1 prevents the cutter from backing away from the work4 ,this adjusting screw plate has its screw holes slotted to avoid removing the screws when it becomes necessary to remove the plate and cutter for sharpening4 ,pilot b is held firmly to the tool body by set-screw r4 ,the hole s through the shank makes it easy to remove the pilot1 in case this is necessary4 ,a pilot box-tool for finishing another type of ball bearing cone is shown at ,b4 ,the shape of the work itself is indicated by the dotted lines a and by the detail view4 ,this tool is somewhat similar in its construction to the one just described4 ,the cutters b and c are inverted and are used to face the flange at d and to turn it to the proper diameter4 ,these cutters are held by the clamp f and screws g and are adjusted forward by the screw h4 ,the cutter j1 which operates on top of the stock1 rests on a bolster1 of the proper angle and is adjusted up or down by the screws k4 ,the clamp l1 which binds against this tool1 is beveled to correspond with the angle of the tool4 ,this clamp is secured by the collar-screw shown and it is leveled by set-screws s4 ,the adjusting screw p prevents the cutter from slipping back4 ,the holes in the adjusting-screw plate are also slotted in this case so that it will not be necessary to remove any screws when the cutter has to be taken out of the holder4 ,a box-tool for finishing a treadle-rod cone for a sewing machine is shown at ,c4 ,this tool is also of the pilot type4 ,the cutters in it operate on opposite sides of the cone a4 ,the inverted cutter b sizes the cylindrical part of the cone1 while the front cutter d is set at the proper angle to finish the tapered part4 ,the rear cutter b is held in place by the clamp g and a collar screw4 ,it is adjusted forward by the screw h in the plate i which is held by screws as shown4 ,the pilot is retained by a set-screw1 and it is easily removed by inserting a small rod in the hole l which passes through the shank4 ,the cutter d is held by clamp m and is adjusted by screw n which passes through a tapped hole in plate o4 ,the screw holes in both the adjusting plates i and o are slotted to facilitate their removal4 ,the box-tool illustrated at ,a1 ,fig4 #aj1 is used for finishing the bushing of a double-taper cone bearing a4 ,the cutters are so arranged that they all cut on the center2 that is1 the cutting edges lie in a horizontal plane4 ,the inverted cutter b at the rear forms the short angular surface1 and the cutter c in front forms the long tapering part of the bearing4 ,the large diameter is turned1 to size by cutter d4 ,the pilot e has a bearing in the bore nearly equal to the length of the work and it is provided with oil grooves1 as shown4 ,the taper shank of this pilot is tapped for the screw i which extends the whole length of the shank and is used to draw the pilot back to its seat4 ,it is not necessary to remove adjusting-screw plate k to take out the cutter b1 as the latter can be drawn out from the front after the collar-screw m is loosened4 ,the cutter c is removed by taking off the adjusting-screw plate s after loosening the collar-screw n4 ,the cutter d is held in a dove-tailed slot by two headless set-screws q4 ,it is also backed up by an adjusting screw in the plate s4 ,these adjusting screws should all have fine threads1 say from #cb to #dj per inch1 and be nicely fitted so they will not loosen after being adjusted4 ,the box-tools shown at ,b and ,c1 ,fig4 #aj1 are for turning the sides of a loose pulley for a sewing machine4 ,this pulley 7shown by the dotted lines7 is finished in two operations4 ,the box-tool for finishing the side of the pulley on which the hub projects beyond the rim1 is shown at ,b4 ,the inverted cutter a1 which faces the end of the hub1 is held by a clamp c 7clearly shown in the end view7 from the under side and it has no adjustment4 ,the collar-screw d is tapped into this clamp1 which is prevented from getting out of place by the dowel-pin f4 ,the pilot g is made small in the shank1 so that tool a can be so placed as to insure the removal of all burrs around the bore of the hub4 ,the pilot is held by a set-screw and it is provided with oil grooves4 ,the cutter j sizes the outside of the hub1 and the cutter k faces the side of the pulley rim4 ,these cutters are both held by the clamp l and the collar-screw m4 ,no side plates are used on this tool1 and the cutters are all easily removed4 ,illustration3 ,fig4 #aj4 ,examples of ,box-tool ,designs ,sketch ,c shows the box-tool used for the second operation4 ,as the hub is flush with the rim on the side for which this tool is intended1 it needs only one cutter to face both4 ,this is done by the wide cutter a which is held in a dove-tailed slot in the front of the tool and is fastened by the clamp b and collar-screw c4 ,the bushing d1 in which the end of the work arbor is supported1 is held by the collar-screw e1 and to obtain the necessary compression1 the body of the tool is slotted as far back as f4 ,this bushing is provided with oil grooves and one side is cut away to clear the cutter a4 ,the pilot end of the arbor on which the work is mounted is #a_/af inch smaller than the bore of the pulley1 which allows the cutter to be set in far enough to prevent any burr which might form at the edge of the bore4 ,a disk i is inserted back of bushing d1 so that the latter may be easily removed by passing a rod through the hollow shank4 ,the special chuck used for this second operation on the loose pulley is screwed onto the spindle1 and the work is mounted on a projecting arbor and driven by the pins engaging holes in the pulley web4 ,the arbor is made a driving fit for the work1 and the end or pilot is a running fit in the bushing of the box-tool4 ,a counterbore in the arbor hub provides clearance for the hub of the pulley which projects beyond the rim on one side4 ,illustration3 ,fig4 #aa4 7,a7 ,hollow ,mill and ,holder4 7,b7 ,spring ,screw-threading ,die and ,releasing ,die-holder ,hollow ,mills4--,a hollow mill such as is shown at ,a in ,fig4 #aa is sometimes used in place of a box-tool 7especially when turning brass7 for short roughing cuts preceding a threading operation4 ,the turning is done by the cutting edges e1 and the turned part enters the mill and is steadied by it4 ,if this type of tool is used for long1 straight cuts1 especially on square stock and when making screws with large heads from the bar1 it should always be followed by a finishing box-tool to insure accurate work4 ,a hollow mill can be sharpened readily by grinding the ends without materially changing the cutting size4 ,a slight adjustment can be obtained by means of the clamp collar shown to the left1 although this is not generally used4 ,when making these mills1 they should be reamed out tapering from the rear to give clearance to the cutting edges4 ,for turning steel1 the cutting edge should be about #a_/aj of the diameter ahead of the center1 whereas for brass1 it should be on the center-line4 ,illustration3 ,fig4 #ab4 ,geometric ,adjustable ,hollow ,milling ,tool ,hollow mills are also made adjustable4 ,the design shown in ,fig4 #ab is especially adapted for brass finishing4 ,it can also be used for taking light cuts on cast iron or steel but its use in place of roughing or finishing box-tools for general use is not recommended4 ,with the exception of the cutters and screws1 the complete tool consists of three parts1 viz41 the holder1 cam1 and ring4 ,the cam serves to adjust the cutters for different diameters4 ,the adjustment is made by the two screws shown1 the amount being indicated by a micrometer scale4 ,when adjusting the cutters for a given diameter1 the use of a hardened steel plug of the required size is advisable1 the cutters being adjusted against the plug4 ,releasing ,die and ,tap ,holders4--,threads are cut in the turret lathe by means of dies for external threading1 and taps for internal threading1 the die or tap being held in a holder attached to the turret4 ,a simple form of releasing die holder is shown at ,b1 ,fig4 #aa4 ,this holder was designed for the spring-screw type of threading die shown to the left4 ,the die is clamped in the holder a by the set-screw shown1 and the shank b of the holder is inserted in the turret hole4 ,holder a has an extension c which passes through the hollow shank4 ,when the die is pressed against the end of the work1 holder a and its extension moves back until lug d on the holder engages lug e on the shank4 ,the die and holder are then prevented from rotating with the work and the die begins to cut a thread4 ,it continues to screw itself onto the work with the turret following1 until the thread has been cut to the required length2 the turret is then stopped and as the die and holder a are drawn forward1 lugs d and e disengage so that the die simply rotates with the work without continuing to advance4 ,the lathe spindle is then reversed and as the turret is moved back by hand1 pin f comes around and enters notch g1 thus holding the die stationary2 the die then backs off from the threaded end4 ,some tap holders are also constructed the same as this die holder1 so far as the releasing mechanism is concerned4 ,there are also many other designs in use1 some of which operate on this same principle4 ,illustration3 ,fig4 #ac4 ,geometric ,self-opening and ,adjustable ,screw-cutting ,die ,head ,self-opening ,die ,heads4--,the type of die holder shown at ,b in ,fig4 #aa is objectionable because of the time required for backing the die off the threaded end2 hence1 self-opening dies are extensively used in turret lathe work4 ,as the name implies1 this type of die1 instead of being solid1 has several chasers which are opened automatically when the thread has been cut to the required length4 ,the turret can then be returned without reversing the lathe spindle4 ,the dies are opened by simply stopping the travel of the turret slide1 the stop-rod for the feed of the turret being adjusted to give the proper amount of travel4 ,illustration3 ,fig4 #ad4 ,geometric ,collapsing ,tap ,a well-known die head of the self-opening type is shown in ,fig4 #ac4 ,the dies open automatically as soon as the travel of the head is retarded1 or they can be opened at any point by simply holding back on the turnstile or lever by which the turret slide is moved4 ,the die is closed again by means of the small handle seen projecting at right-angles from the side of the head4 ,the closing may be done by hand or automatically by screwing a pin into a threaded hole opposite the handle and attaching a small piece of flat steel to the back edge of the turret slide4 ,the latter will then engage the pin as the turret revolves1 thus closing the die head4 ,this die head has a roughing and finishing attachment which is operated by handle ,a4 ,when this handle is moved forward1 the dies are adjusted outward #j4ja inch for the roughing cut1 whereas returning the handle closes and locks the dies for the finishing cut4 ,the die head has a micrometer scale which is used when making slight adjustments to compensate for the wear of the chasers or to make either a tight-or a loose-fitting thread4 ,collapsing ,taps4--,the collapsing tap shown in ,fig4 #ad is one of many different designs that are manufactured4 ,they are often used in turret lathe practice in place of solid taps4 ,when using this particular style of collapsing tap1 the adjustable gage ,a is set for the length of thread required4 ,when the tap has been fed to this depth1 the gage comes into contact with the end of the work1 which causes the chasers to collapse automatically4 ,the tool is then withdrawn1 after which the chasers are again expanded and locked in position by the handle seen at the side of the holder4 ,in all threading operations1 whether using taps or dies1 a suitable lubricant should be used1 as a better thread is obtained and there is less wear on the tools4 ,lard oil is a good lubricant1 although cheaper compounds give satisfactory results on many classes of work4 ,miscellaneous ,turret ,lathe ,tools4--,the chamfering tool shown at ,a1 ,fig4 #ae1 is used for pointing the end of a bar before running on a roughing box-tool4 ,this not only finishes the end of the bar but provides an even surface for the box-tool to start on4 ,the cutter is beveled on the end to form a cutting edge and it is held at an angle4 ,the back-rest consists of a bell-mouthed1 hardened tool-steel bushing which supports the bar while the cut is being taken4 ,the stop gages ,b and ,c are used in the turret to govern the length of stock that is fed through the spindle4 ,when a finished piece has been cut off1 the rough bar is fed through the spindle and up against the stop gage1 thus locating it for another operation4 ,this gage may be a plain cylindrical piece of hardened steel1 as at ,b1 or it may have an adjusting screw as at ,c2 for special work1 different forms or shapes are also required4 ,the stop gages on some machines1 instead of being held in the turret1 are attached to a swinging arm or bracket that is fastened to the turret slide and is swung up in line with the spindle when the stock is fed forward4 ,the center drilling tool ,d is designed to hold a standard combination center drill and reamer4 ,this type of tool is often used when turning parts that must be finished afterwards by grinding1 to form a center for the grinding machine4 ,the adjustable turning tool ,e is used for turning the outside of gear blanks1 pulley hubs or the rims of small pulleys4 ,the pilot a enters the finished bore to steady the tool1 and cutter b is adjusted to turn to the required diameter4 ,illustration3 ,fig4 #ae4 ,various ,types of ,tools for the ,turret ,lathe ,the cutting-off tool-holder ,f 7which is held on the cross-slide of the turret lathe7 is usually more convenient than a regular toolpost1 as the blade can be set closer to the chuck4 ,the blade is held in an inclined position1 as shown1 to provide rake for the cutting edge2 the inclined blade can also be adjusted vertically1 a limited amount1 by moving it in or out4 ,the multiple cutting-off tool ,g holds two or more blades and is used for cutting off several washers1 collars1 etc41 simultaneously4 ,by changing the distance pieces between the cutters1 the latter are spaced for work of different widths4 ,the flat drill holder ,h is used for drilling short holes1 and also to form a true spot or starting point for other drills4 ,knurling tools are shown at ,i and ,j4 ,the former is intended for knurling short lengths and is sometimes clamped on top of the cut-off tool on the cross-slide1 the end being swung back after knurling 7as shown by the dotted lines7 to prevent interference with the work when the cutting-off tool is in operation4 ,the knurling tool ,j has a shank and is held in the turret4 ,the two knurls are on opposite sides of the work so that the pressure of knurling is equalized4 ,by adjusting the arms which hold the knurls1 the tool can be set for different diameters4 ,three styles of drill holders are shown at ,k1 ,l and ,m4 ,holder ,k is provided with a split collet 7seen to the left7 which is tightened on the drill shank by a set-screw in the holder4 ,this holder requires a separate collet for each size drill4 ,the taper shank drill holder ,l has a standard taper hole into which the shank of the drill is inserted4 ,the adjustable type of holder ,m is extensively used1 especially on small and medium sized machines when several sizes of drills are necessary4 ,this holder is simply a drill chuck fitted with a special shank4 ,for large drills the plain style of holder ,k is recommended1 and if only a few sizes of drills are required1 it is more satisfactory and economical than the adjustable type4 ,the various types of small turret lathe tools referred to in the foregoing for turning1 threading1 tapping1 knurling1 etc41 are a few of the many different designs of tools used in turret lathe practice4 ,naturally1 the tool equipment for each particular job must be changed somewhat to suit the conditions governing each case4 ,the tools referred to1 however1 represent in a general way1 the principal types used in ordinary practice4 ,some of the more special tools are shown in connection with examples of turret lathe work1 which are referred to in the following4 ,turning ,gasoline ,engine ,pistons in ,turret ,lathe4--,the making of pistons for gas engines1 especially in automobile factories1 is done on such a large scale that rapid methods of machining them are necessary4 ,the plan view ,a1 ,fig4 #af1 shows the turret lathe tools used in one shop for doing this work4 ,as is often advisable with work done in large quantities1 the rough castings are made with extra projections so arranged as to assist in holding them4 ,these projections are1 of course1 removed when the piece is completed4 ,in this case the piston casting a has a ring about #a-a_/d inch long and a little less in diameter than the piston1 at the chucking end4 ,the piston is held in suitable chuck jaws b which are tightened against the inside of this ring4 ,the set-screws in these special jaws are then tightened1 thus clamping the casting between the points of the screws and the jaws4 ,this method of holding permits the whole exterior of the piston to be turned1 since it projects beyond the chuck jaws4 ,this is the object in providing the piston with the projecting ring by which it is held4 ,illustration3 ,fig4 #af4 7,a7 ,method of ,boring and ,turning ,pistons in ,gisholt ,lathe4 7,b7 ,special ,chuck and ,tools for ,turning1 ,boring and ,cutting ,off ,eccentric ,piston ,rings ,the first operation consists in rough-boring the front end of the piston4 ,the double-ended cutter n is held in boring-bar m1 which is1 in turn1 supported by a drill-holder1 clamped to one of the faces of the turret4 ,this bar is steadied by a bushing in the drill support c which is attached to the carriage1 and may be swung into or out of the operating position1 as required4 ,after this cut is completed1 the turret is revolved half way around and the casting is finish-bored in a similar manner1 with double-ended cutter n#a held in bar m#a1 the drill support being used as in the previous case4 ,the support is then turned back out of the way to allow the turning tools in the turret toolpost to be used4 ,the outside of the piston is next rough-turned with tool k in the turret toolpost1 which is revolved to bring this cutter into action4 ,the toolpost is then turned to the position shown1 and the outside is finish-turned by tool j1 which takes a broad shaving cut4 ,the turret tool-holder is again revolved to bring form tool l into position4 ,this tool cuts the grooves for the piston rings4 ,suitable positive stops are1 of course1 provided for both the longitudinal and cross movements of the turret toolpost4 ,in the second operation1 the piston a is reversed and held in soft jaws1 which are used in place of the hardened jaws b shown in the illustration4 ,these jaws are bored to the outside diameter of the piston1 so that when closed1 they hold the work true or concentric with the lathe spindle4 ,in this operation the chucking ring by which the piston was previously held is cut off1 and the end of the piston is faced true4 ,if the crank-pin hole is to be finished1 a third operation is necessary1 a self-centering chuck-plate and boring and reaming tools being used4 7,these are not shown in the illustration47 ,turning ,piston ,rings in ,turret ,lathe4--,one method of turning piston rings is shown at ,b in ,fig4 #af4 ,the piston rings are cut from a cast-iron cylindrical piece which has three lugs b cast on one end and so arranged that they may be held in a three-jawed chuck4 ,this cylindrical casting is about #aj inches long1 and when the rings are to have their inside and outside surfaces concentric1 the casting is held by the lugs in the regular jaws furnished with the chuck4 7,the arrangement used for turning and boring eccentric rings1 which is that shown in the illustration1 will be described later47 ,the casting a1 from which the rings are made1 is first rough-bored with double-ended cutter n in boring-bar m1 after which it is finish-bored with cutter n#a in bar m#a4 ,while taking these cuts1 the bars m and m#a are supported by their extension ends which enter bushing r located in the central hole of the chuck4 ,this furnishes a rigid support so that a heavy cut can be taken4 ,the outside of the casting is next rough-turned with tool k1 held in the turret toolpost4 ,this toolpost is then revolved to bring tool j into position1 by which the outside is turned true to size1 a broad shaving chip being taken4 ,the toolpost is again swung around1 to bring the cutting-off tool-holder l into position4 ,this holder contains four blades set the proper distance apart to give rings of the desired width4 ,each blade1 from right to left1 is set a little back of the preceding one1 so that the rings are cut off one after the other1 the outer rings being supported until they are completely severed4 ,after the first four rings are cut off1 the carriage is moved ahead to a second stop1 and four more rings are severed1 this operation being continued until the casting has been entirely cut up into rings4 ,when the bore of the ring is to be eccentric with the outside1 the holding arrangement shown in the illustration is used4 ,the casting a is bolted to a sliding chuck-plate c1 and the outside is rough-turned with tool k in the toolpost4 ,finishing tool j is then brought into action1 and the outside diameter is turned accurately to size4 ,then the sliding chuck-plate c1 carrying the work1 is moved over a distance equal to the eccentricity desired1 and the work is bored with cutters n and n#a as in the previous case4 ,the turret toolpost is next revolved and the tools l are used for cutting off the rings4 ,the reason for finishing the outside first is to secure smooth rings in cutting off1 as this operation should be done when the work is running concentric with the bore1 rather than with the exterior surface4 ,it will be evident that this method gives a far greater output of rings than is possible by finishing them in the more primitive way on engine lathes4 ,the faces of the rings may be finished in a second operation if desired1 or they may be ground1 depending on the method used in the shop where the work is being done1 and the accuracy required4 ,illustration3 ,fig4 #ag4 ,turning ,gasoline ,engine ,pistons in ,pratt ,whitney ,turret ,lathe ,piston ,turning in ,pratt and ,whitney ,turret ,lathe4--,a turret lathe equipped with tools for turning1 facing and grooving automobile gasoline engine pistons is shown in ,fig4 #ag4 ,the piston is held on an expanding pin chuck which is so constructed that all of the pins are forced outward with equal pressure and automatically conform to any irregularities on the inside of the piston4 ,tool ,a rough-turns the outside1 and just as this tool completes its cut1 a center hole is drilled and reamed in the end of the piston by combination drill and reamer ,b4 ,the turret is then indexed one-half a revolution and a finishing cut is taken by tool ,c4 ,after the cylindrical body of the piston has been turned1 tools held in a special holder ,e attached to the cut-off slide are used to face the ends of the piston and cut the packing-ring grooves4 ,while the grooves are being cut1 the outer end of the piston is supported by center ,d4 ,the center hole in the end also serves to support the piston while being ground to the required diameter in a cylindrical grinding machine4 ,the edge at the open end of the piston may also be faced square and the inner corner beveled by a hook tool mounted on the rear cross-slide1 although this is usually done in a separate operation4 7,this provides a true surface by which to hold this end when grinding47 ,illustration3 ,fig4 #ah4 ,pratt ,whitney ,turret ,lathe equipped with ,special ,attachment for ,turning ,eccentric ,piston ,rings ,this illustration 7,fig4 #ag7 shows very clearly the stops which automatically disengage the turret feed4 ,a bracket ,f is bolted to the front of the bed and contains six stop-rods ,g 7one for each position or side of the turret74 ,when one of these stop-rods strikes lever ,h1 the feed is disengaged1 the stop being adjusted to throw out the feed when the tool has completed its cut4 ,lever ,h is automatically aligned with the stop-rods for different sides of the turret by a cam ,j on the turret base4 ,a roller ,k bears against this cam and1 through the connecting shaft and lever shown1 causes lever ,h to move opposite the stop-rod for whatever turret face is in the working position4 ,lever ,l is used for engaging the feed and lever ,r for disengaging it by hand4 ,the indexing of the turret at the end of the backward movement of the slide is controlled by stop ,m against which rod ,n strikes1 thus disengaging the lock bolt so that the turret can turn4 ,this stop ,m is adjusted along the bed to a position depending upon the length of the turret tools and the distance the turret must move back to allow the tools to clear as they swing around4 ,illustration3 ,fig4 #ai4 ,tool ,equipment for ,machining ,worm ,gear ,blanks--,davis ,turret ,lathe ,attachment for ,turning ,piston ,rings4--,fig4 #ah shows a special attachment applied to a ,pratt ,whitney turret lathe for turning eccentric1 gas-engine piston rings4 ,the boring of the ring casting1 turning the outside and cutting off the rings1 is done simultaneously4 ,the interior of the casting is turned concentric with the lathe spindle by a heavy boring-bar1 the end of which is rigidly supported by a bushing in the spindle4 ,the slide which carries the outside turning tool is mounted on a heavy casting which straddles the turret4 ,the outside of the ring casting is turned eccentric to the bore as a result of an in-and-out movement imparted to the tool by a cam on shaft ,a which is rotated from the lathe spindle through the gearing shown4 ,for each revolution of the work1 the tool recedes from the center and advances toward it an amount sufficient to give the required eccentricity4 ,when the turning and boring tools have fed forward about #b inches1 then the cutting-off tools which are held in holder ,b come into action4 ,the end of each cutting-off tool1 from right to left1 is set a little farther away from the work than the preceding tool1 so that the end rings are always severed first as the tools are fed in by the cross-slide4 ,a number of the completed rings may be seen in the pan of the machine4 ,illustration3 ,fig4 #bj4 ,turning ,bevel ,gear ,blanks in ,davis ,turret ,lathe--,first ,operation ,turning ,worm-gear ,blanks in ,turret ,lathe4--,this is a second operation1 the hub of worm-gear blank ,g 7,fig4 #ai7 having previously been bored1 reamed1 and faced on the rear side4 ,the casting is mounted upon a close-fitting arbor attached to a plate bolted to the faceplate of the lathe1 and is driven by two pins which engage holes on the rear side4 ,the rim is first rough-turned by a tool ,a which operates on top1 and the side is rough-faced by a toothed or serrated cutter ,b4 ,a similar tool-holder having a tool ,c and a smooth cutter ,d is then used to turn the rim to the required diameter and finish the side4 ,the end of the hub is faced by cutters mounted in the end of bars ,e and ,f1 one being the roughing cutter and the other the finishing cutter4 ,the work arbor projects beyond the hub1 as will be seen1 and forms a pilot that steadies these cutter bars4 ,the curved rim of the gear is turned to the required radius 7preparatory to gashing and bobbing the worm-wheel teeth7 by a formed tool ,h held on the cross-slide4 ,illustration3 ,fig4 #ba4 ,second ,operation on ,bevel ,gear ,blanks ,turning ,bevel ,gear ,blanks4--,fig4 #bj shows a plan view of the tools used for the first turning operation on bevel gear blanks 7these gears are used for driving drill press spindles74 ,the cored hole is beveled true at the end by flat drill ,a to form a true starting surface for the three-fluted drill ,b which follows4 ,the hole is bored close to the required size by a tool 7not shown7 held in the end of bar ,c1 and it is finished by reamer ,d4 ,the cylindrical end of the gear blank or hub is rough-and finish-turned by tools held in holders ,e and ,f1 respectively4 7,these holders were made to set at an angle of #de degrees1 instead of being directly over the work1 as usual1 so that the cutters would be in view when setting up the machine47 ,it will be noted that the chuck is equipped with special jaws which fit the beveled part of the casting4 ,illustration3 ,fig4 #bb4 ,sectional ,view of ,tapering ,mold ,shell which is turned in ,hartness ,flat ,turret ,lathe1 as illustrated in ,figs4 #bc to #bg1 ,inclusive ,the second and final operation on this blank is shown in ,fig4 #ba4 ,the work ,a is held by a special driver plate attached to the faceplate of the machine4 ,this driver plate has two pins which engage holes drilled in the gear blank and prevent it from rotating4 ,the blank is also held by a bolt ,b which forces a bushing against the cylindrical end4 ,first1 the broad beveled side which is to be the toothed part of the gear1 is rough-turned by toothed cutters ,c1 and a recess is formed in the end of the blank1 by a turning tool in this same tool-holder4 ,a similar tool-holder ,e1 having finishing cutters1 is then used to finish the bevel face and recess4 ,the other tools seen in the turret are not used for this second operation4 ,the rear bevel is roughed and finished by tools and held on the cross-slide4 ,shell ,turning ,operation in ,flat ,turret ,lathe4--,the flat turret lathe is so named because the turret is a flat circular plate mounted on a low carriage to secure direct and rigid support from the lathe bed4 ,the tools1 instead of being held by shanks inserted in holes in the turret1 are designed so that they can be clamped firmly onto the low circular turret plate4 ,an interesting example of flat turret lathe work is shown in ,fig4 #bb4 ,this is a steel shell which must be accurately finished to a slight taper1 both inside and out1 threaded and plain recesses are required at the ends1 and1 in addition1 one or two minor operations are necessary4 ,this work is done in the ,hartness flat turret lathe1 built by the ,jones ,lamson ,machine ,co4 ,the shells are turned from cold-drawn seamless steel tubing1 having a carbon content of #j4bj per cent1 and they are finished at the rate of one in nine minutes4 ,the tubing comes to the machine in #ab-;foot lengths1 and the tube being operated upon is1 of course1 fed forward through the hollow spindle as each successive shell is severed4 ,illustration3 ,fig4 #bc4 ,first ,operation on ,shell ,illustrated in ,fig4 #bb--,rough-turning and ,boring ,in finishing this shell1 five different operations are required4 ,during the first operation the shell is rough-bored and turned by one passage of a box-tool1 ,fig4 #bc1 and the recess ,a1 ,fig4 #bb1 at the outer end1 is finished to size by a second cutter located in the boring-bar close to the turret4 ,the turret is then indexed to the second station which brings the threading attachment ,g into position1 as shown in ,fig4 #bd4 ,after the thread is finished1 the recess ,b1 ,fig4 #bb1 is turned by a flat cutter ,k1 ,fig4 #be4 ,the inner and outer surfaces are then finished to size by a box-tool mounted on the fourth station of the turret and shown in position in ,fig4 #bf4 ,the final operation1 ,fig4 #bg1 is performed by three tools held on an auxiliary turret cross-slide1 and consists in rounding the corners at b and c1 ,fig4 #bb1 and severing the finished shell4 ,illustration3 ,fig4 #bd4 ,second ,operation--,cutting ,internal ,thread ,one of the interesting features connected with the machining of this shell is the finishing of the inner and outer tapering surfaces4 ,the taper on the outside is #c_/cb inch ,per foot1 while the bore has a taper of only #a_/fd inch per foot1 and these surfaces are finished simultaneously4 ,the box-tool employed is of a standard type1 with the exception of an inserted boring-bar1 and the taper on the outside is obtained by the regular attachment which consists of a templet ,d 7,fig4 #bc7 of the required taper1 that causes the turning tool to recede at a uniform rate as it feeds along4 ,to secure the internal taper1 the headstock of the machine is swiveled slightly on its transverse ways by the use of tapering gibs4 ,by this simple method1 the double taper is finished to the required accuracy without special tools or equipment4 ,as those familiar with this machine know1 the longitudinal movements of the turret as well as the transverse movements of the headstock are controlled by positive stops4 ,the headstock of this machine has ten stops which are mounted in a revolving holder and are brought into position1 as required1 by manipulating a lever at the front4 ,the stops for length1 or those controlling the turret travel1 are divided into two general groups1 known as ,a and ,b4 ,each of these groups has six stops so that there are two stops for each of the six positions or stations of the turret1 and1 in addition1 five extra stops are available for any one tool1 by the engagement of a pin at the rear of the turret4 ,the change from the ,a to the ,b stops is made by adjusting lever ,l1 ,fig4 #bf1 which also has a neutral position4 ,illustration3 ,fig4 #be4 ,third ,operation--,turning ,recess at ,rear ,end2 ,tool is shown withdrawn ,after the box-tool for the roughing cut1 shown at work in ,fig4 #bc1 has reached the end of its travel1 further movement is arrested by a stop of the ,a group4 ,the outside turning tool is then withdrawn by operating lever ,e and the turret is run back and indexed to the second station1 thus bringing the threading attachment into position4 ,the surface speed of #acj feet per minute which is used for turning is reduced to about #cj feet per minute for threading by manipulating levers ,h1 ,fig4 #bd4 ,after the turret is located by another stop of the ,a group1 the threading attachment is made operative by depressing a small plunger ,i1 which connects a vertical driving shaft from the spindle with the splined transmission shaft ,j4 ,a reciprocating movement is then imparted to the thread chaser t which advances on the cutting stroke and then automatically retreats to clear the thread on the return4 ,this movement is repeated until the thread is cut to the proper depth1 as determined by one of the stops for the headstock4 ,while the thread is being cut1 the carriage is locked to the bed by the lever ,n1 ,fig4 #bf4 ,it was found necessary to perform the threading operation before taking the outside finishing cut1 owing to a slight distortion of the shell wall1 caused by the threading operation4 ,illustration3 ,fig4 #bf4 ,fourth ,operation--,finishing the ,bore and ,outside ,after the thread is finished1 the turret is turned to the third station as shown in ,fig4 #be1 and tool ,k for the inner recess ,b1 ,fig4 #bb1 is brought into position and fed to the proper depth1 as determined by another cross-stop4 ,the turret is also locked in position for this operation4 ,the finishing cuts for the bore and the outside are next taken by a box-tool which is shown near the end of its cut in ,fig4 #bf4 ,this box-tool is similar to the one used for roughing1 but it is equipped with differently shaped cutters to obtain the required finish4 ,the outside turning tool has a straight cutting edge set tangent to the cylindrical surface and at an angle1 while the boring tool has a cutting edge of large radius4 ,an end view of this box-tool is shown in ,fig4 #bg4 ,a reduced feed is employed for the finishing cut1 and the speed is increased to #acj feet per minute1 which is the same as that used for roughing4 ,illustration3 ,fig4 #bg4 ,fifth ,operation--,rounding ,ends1 ,scoring ,large ,end1 and ,cutting ,off ,during the next and final operation1 the turret1 after being indexed to the position shown in ,fig4 #bg1 is first located by a stop of the ,a group so that the cutting-off tool ,r in front can be used for rounding the corner b1 ,fig4 #bb4 ,the stop lever ,l is then shifted and the turret is moved to a second stop of the ,b group4 ,the corner c is then rounded and the shell is scored at d by two inverted tools ,s and ,t at the rear1 after which the finished work is severed by the cut-off tool at the front4 ,the cross-movement of these three tools is controlled by positive stops on the cross-slide1 and the latter is moved to and fro by hand lever ,o4 ,after the shell is cut off1 the stop ,m1 mounted on the turret1 ,fig4 #bf1 is swung into position1 and the tube is automatically fed forward to the swinging stop by the roll feed1 as soon as the chuck is released by operating lever ,q4 ,this completes the cycle of operations4 ,a copious supply of lubricant is1 of course1 furnished to the tools during these operations1 and the two boring-tool shanks are hollow so that lubricant can be forced through them and be made to play directly upon the cutters4 ,chuck ,work in ,flat ,turret ,lathe4--,two examples of chuck work on the ,acme combination flat turret lathe are shown in ,figs4 #bh and #bi4 ,fig4 #bh shows the tool equipment for turning a cylindrical part ,a which is held in a three-jaw universal chuck4 ,the front flange is first rough-turned by a bent turning tool ,b4 ,the diameter is regulated by one of the cross-stops at ,d which has been previously set and controls the movement of the turret cross-slide4 ,the longitudinal feed is disengaged when the flange has been turned1 by an independent stop4 ,this machine has twelve longitudinal stops1 there being one for each turret face and six auxiliary stops1 in addition to the stops for the cross-slide4 ,illustration3 ,fig4 #bh4 ,tool ,equipment for ,turning ,scroll ,gear ,blank on ,acme ,flat ,turret ,lathe ,after roughing the flange1 the turret carriage is locked or clamped rigidly to the bed to prevent any lengthwise movement1 and the back face of the front flange is rough-turned by tool ,b in to the diameter of the hub which is indicated by a micrometer dial on the cross-feed screw4 ,the carriage is then unlocked and auxiliary stop ,no4 #g is engaged 7by turning a knob at the front of the slide7 and the cylindrical hub is turned back to the rear flange1 the feed being disengaged by the auxiliary stop just as the tool reaches the flange4 ,the cross-slide is now moved outward1 longitudinal auxiliary stop ,no4 #h is engaged1 the turret slide is moved against the stop1 the carriage is locked and the front sides of both the front and rear flanges are rough-faced by tools ,b and ,c4 ,the turret is next indexed and the hole rough-bored by cutter ,e4 ,after again indexing the turret1 the hub and flanges are finish-turned and faced by tools ,f and ,g1 as described for the rough-turning operation4 ,the final operation is that of finishing the bore by cutter ,h4 ,illustration3 ,fig4 #bi4 ,acme ,flat ,turret ,lathe ,arranged for ,turning ,roller ,feed ,body ,the operation shown in ,fig4 #bi is that of turning the body of a roller feed mechanism for a turret lathe4 ,the casting is held in a three-jaw universal chuck and it is first rough-bored by tool ,a4 ,the turret is then indexed and the side of the body and end of the hub are rough-faced by tools at ,b4 ,the turret is again indexed for rough-turning the outside of the hub and body1 by tools ,c and ,d4 ,similar tools ,e and ,f are then used to finish these same surfaces1 after which the end of the hub and side of the body are finished by tools ,g and ,h similar to those located at ,b4 ,the final operation is that of finishing the bore by tool ,j and cutting a groove in the outside of the hub by the bent tool ,k4 ,illustration3 ,fig4 #cj4 ,turret and ,head of ,jones ,lamson ,double-spindle ,flat ,turret ,lathe ,double-spindle ,flat ,turret ,lathe4--,the extent to which modern turning machines have been developed1 especially for turning duplicate parts in quantity1 is illustrated by the design of turret lathe the turret and head of which is shown in ,fig4 #cj4 ,this machine has two spindles and a large flat turret which holds a double set of tools1 so that two duplicate castings or forgings can be turned at the same time4 ,it was designed primarily for chuck work and can be used as a single-spindle machine if desirable4 ,when two spindles are employed for machining two duplicate parts simultaneously1 considerably more time is required for setting up the machine than is necessary for the regular single-spindle type1 but it is claimed that the increased rate of production obtained with the two-spindle design more than offsets this initial handicap4 ,the manufacturers consider the single-spindle machine the best type for ordinary machine building operations1 regardless of whether the work is turned from the bar or is of the chucking variety4 ,on the other hand1 the double-spindle type is preferred when work is to be produced in such quantities that the time for setting up the machine becomes a secondary consideration4 ,illustration3 ,fig4 #ca4 ,diagram showing ,tool ,equipment and ,successive ,steps in ,machining ,sprocket ,blanks on ,double-spindle ,flat ,turret ,lathe ,when the double-spindle machine is used as a single-spindle type1 a chuck #ag inches in diameter is used1 and when both spindles are in operation1 two #i-;inch chucks are employed4 ,the general outline of the turret is square1 and the tools are rigidly held1 with a minimum amount of overhang1 by means of tool-blocks and binding screws connected with the clamping plates4 ,two duplicate sets of tools are clamped to each side of the turret and these operate simultaneously on the two pieces held in the chucks or on faceplates4 ,primarily the turret is used in but four positions1 but when a #ag-;inch chuck or faceplate is employed1 corner blocks may be held by the clamping plates in which tools are supported1 giving1 if necessary1 four additional operations by indexing the turret to eight positions4 ,a typical job to demonstrate the application of the double-spindle flat turret lathe is illustrated in ,fig4 #ca4 ,the parts to be turned are sprocket wheels which are held in the two #i-;inch chucks4 ,at the first position of the turret 7which is the one illustrated71 the inside is rough-bored by tools ,a4 ,at the second position of the turret1 tools ,b rough-face the inner sides of the flanges2 tools ,c face the outer sides of the flanges1 while tools ,d turn the faces of the flanges4 ,at the third position of the turret1 tools ,e finish-turn the inside of the flanges2 tools ,f finish-turn the outside of the flanges1 while tools ,g finish the faces of the flanges4 ,at the fourth position of the turret1 tools ,h finish-bore the sprockets2 tools ,i complete the turning on the outside of the flanges1 while tools ,j accurately size the interior of the flanges4 ,with the double-spindle flat turret lathe1 each operation is a double operation1 and the speeds are varied according to the nature of the cut2 thus1 if at one position of the turret1 the tools are required to rough out the work1 this may be done rapidly1 for it has no bearing on the other operations that are subsequently performed4 ,furthermore1 if the following operation has to be performed with great care1 this may be done without reducing the speed of the less exacting operations4 ,illustration3 ,fig4 #cb4 ,potter ,johnston ,automatic ,chucking and ,turning ,machine ,automatic ,chucking and ,turning ,machine4--,the chucking and turning machine shown in ,fig4 #cb is automatic in its operation1 the feeding of the tools1 indexing of the turret1 etc41 being done automatically after the machine is properly arranged1 and the work is placed in the chuck4 ,this machine is adapted to turning and boring a great variety of castings1 forgings or parts from bar stock1 and it is often used in preference to the hand-operated turret lathe1 especially when a great many duplicate parts are required4 ,it is provided with mechanism for operating the cross-slide1 feeding the turret slide forward1 returning it rapidly1 rotating the turret to a new position1 and feeding it forward quickly for taking a new cut4 ,the cross-slide and turret-slide movements are effected by cams mounted on the large drum ,e seen beneath the turret1 while the various speed and feed changes are effected by dogs and pins carried on disk ,d which is keyed to the same shaft that the cam drum is mounted upon4 ,this shaft with the cam drum and governing disk ,d1 makes one revolution for each piece of work completed4 ,the cams for operating the turret slide are mounted upon the periphery of drum ,e4 ,the roll which engages the angular faces of these cams and imparts movement to the turret is carried by an intermediate slide which has rack teeth engaging a pinion on the square shaft ,c4 ,by turning this shaft with a crank1 the position of the turret-slide1 with relation to the cam1 may be adjusted for long or short work and long or short tools1 as may be required4 ,illustration3 ,fig4 #cc4 ,rear ,view of ,machine showing the ,cross-slide ,mechanism1 ,driving ,gearing1 etc4 ,the cams which operate the cross-slide are mounted on the right-hand end of drum ,e and actuate the yoke ,a 7see ,fig4 #cc7 which extends diagonally upward4 ,the rear end of this yoke has rack teeth meshing with the teeth of a segmental pinion1 which is fastened to rock-shaft ,b4 ,at the headstock end1 this rock-shaft carries another segmental pinion meshing with rack teeth formed on the cross-slide4 ,the movement imparted to the yoke by the cams is thus transmitted through the pinions and rock-shaft to the cross-slide4 ,illustration3 ,fig4 #cd4 ,the ,automatic ,controlling ,mechanism for ,feeds and ,speeds ,the cam drum ,e is driven by a pinion meshing with a gear attached to its front side4 ,this pinion is driven through a train of gearing from pulley ,l 7see ,fig4 #cd7 which is belted to the spindle4 ,the feeds are thus always dependent on the spindle speed4 ,by means of epicyclic gearing and suitable clutches1 the motion thus derived from the spindle may be made rapid for returning the turret to be indexed and then advancing it to the cutting position again1 or very slow for the forward feed when the tools are at work4 ,these changes from slow to fast or vice versa are controlled by disk ,d4 ,this disk carries pins which strike a star wheel located back of the disk at the top1 and as this star wheel is turned1 the speeds are changed by operation of the gearing and clutches referred to4 ,the first pin ,m that strikes the star wheel advances it one-sixth of a rotation1 changing the feed from fast to slow2 the next pin that strikes it advances it another sixth of a rotation1 changing the feed from slow to fast and so on4 ,by adjusting the pins for each piece of work1 the feed changes are made to take place at the proper time4 ,handwheel ,e is geared with the cam-shaft on which the star wheel is mounted1 so that the feeds may be changed by hand if desired4 ,in addition to these feed-changing pins1 disk ,d has a dog which operates a lever by which the feed movement is stopped when the work has been completed4 ,four rates of feed are provided by quick change gearing of the sliding gear type1 operated by handle ,k4 ,with this handle set in the central position1 the feed is disengaged4 ,on the periphery of disk ,d are also clamped dogs or cams ,n1 which operate a horizontal swinging lever ,p connected by a link with vertical lever ,j1 which controls the two spindle speeds with which the machine is provided4 ,either one of these speeds can be automatically engaged at any time1 by adjusting the cams ,n on disk ,d4 ,lever ,h connects or disconnects the driving pulley from the shaft on which it is mounted1 thus starting or stopping the machine4 ,the square shaft ,g serves to operate the drums by hand and is turned with a crank4 ,the rotation of the turret1 which takes place at the rear of its travel1 is1 of course1 effected automatically4 ,a dog1 which may be seen in ,fig4 #cb at the side of the bed1 is set to trip the turret revolving mechanism at the proper point in the travel1 to avoid interference between the tools and the work4 ,the turret is provided with an automatic clamping device4 ,the mechanism first withdraws the locking pin1 unclamps the turret1 revolves it1 then throws in the locking pin and clamps the turret again4 ,example of ,work on ,automatic ,turning ,machine4--,the piece selected for illustrating the setting up and operation of the automatic chucking and turning machine is shown in ,fig4 #ce4 ,this is a second operation1 and a very simple one which will clearly illustrate the principles involved4 ,in the first operation1 the hole was drilled1 bored and reamed1 the small end of the bushing faced1 and the outside diameter finished1 as indicated by the sketch to the left4 7,the enlarged diameter at the end was used for holding the work in the chuck47 ,in the second operation 7illustrated to the right71 the enlarged chucking end is cut off and1 in order to prevent wasting this piece1 it is made into a collar for another part of the machine for which the bushing is intended2 hence1 the outside diameter is turned and the outside end faced1 before cutting off the collar4 ,in addition1 the bushing is recessed in the second operation1 and the outer end faced4 ,in order to have the surfaces finished in the second operation1 concentric with those machined in the first operation1 the chuck is equipped with a set of soft false jaws which have been carefully bored to exactly the diameter of the work to be held4 ,illustration3 ,fig4 #ce4 ,simple ,example of ,work done in ,automatic ,chucking and ,turning ,machine ,the first thing to determine when setting up a machine of this type is the order of operations4 ,in this particular case1 the order is as follows3 ,at the first position of the turret1 the outside collar is rough-turned and the outer end rough-faced4 ,at the second position1 the collar is turned to the required diameter and the outer face is finished4 ,the third face of the turret is not equipped with tools1 this part of the cycle being taken up in cutting off the collar with a cut-off tool on the rear cross-slide4 ,the fourth operation is that of recessing the bushing1 and the fifth operation1 facing the end to remove the rough surface left by the cutting-off tool4 ,the tools ,a and ,b1 ,fig4 #cf1 used for turning the outside of the flange1 are held in brackets ,c bolted to the face of the turret4 ,these brackets are each provided with three holes for carrying turning tool-holders4 ,this arrangement provides for turning a number of diameters at different positions1 simultaneously1 but for this particular operation1 a single cutting tool for each tool-holder is all that is necessary4 ,a special device is used for recessing and will be described later4 ,illustration3 ,fig4 #cf4 ,front ,view of ,machine set up for the ,finishing ,operation on the ,recessed ,bushing and ,collar shown in the ,foreground and in ,fig4 #ce ,determining ,speed and ,feed ,changes4--,as previously mentioned1 the particular machine illustrated in ,fig4 #cb can be arranged for two automatic changes of speed to suit different diameters on the work4 ,the change gears that will give the required spindle speeds should first be selected4 ,these change gears for different speeds are listed on a speed and feed plate attached to the headstock of the machine 7see ,fig4 #cg74 ,it is possible to use one speed from the list given for the fast train of gears1 and one from the list for the slow train1 so long as the same gears are not used in each case4 ,the diameter of the collar on the work shown in ,fig4 #ce is #b-a_/b inches1 and the diameter of the body is #b inches4 ,assuming that the surface speed for this job should be about #dj feet per minute1 a little calculation shows that the #ff revolutions per minute1 given by the fast train of gears1 is equivalent to a surface speed of #dc feet per minute on a diameter of #b-a_/b inches4 ,moreover1 the #gh revolutions per minute obtained from the slow train of gearing1 gives about #da feet per minute on a diameter of #b inches4 ,the spindle gearing indicated for these speeds is1 therefore1 placed in position on the proper studs at the back of the machine4 ,illustration3 ,fig4 #cg4 ,plate on the ,headstock of ,machine ,illustrated in ,fig4 #cb giving the ,speeds and ,feeds ,next we have to determine on which faces of the turret to place the different tools4 ,each turret face is numbered to agree with the corresponding feed cam on the drum4 ,the speed and feed plate 7,fig4 #cg7 gives the various feeds obtainable per revolution of the spindle4 ,as will be seen1 the different cams give different feeds4 ,cam ,no4 #a has a coarse feed suitable for roughing2 cam ,no4 #b a finer feed adapted to finishing1 and so on4 ,since the first operation consists in rough-turning1 cam ,no4 #a is used4 ,cam ,no4 #b1 which gives a finer feed1 is used for the finish-turning operation4 ,cam ,no4 #d1 which is ordinarily used for reaming1 could1 in this case1 be used for recessing1 as this recess is for clearance only and may be bored with a coarse feed4 ,the final operation1 which is that of facing1 can be done with any cam and cam ,no4 #e may be used4 ,it will be understood that for facing operations1 the feeds given do not apply4 ,as the roll passes over the point of the feed cam at the extreme end of the movement1 the feed of the turret slide is gradually slowed down to zero2 since the facing takes place in the last eighth or sixteenth inch of this movement1 it is done at a feed which is gradually reduced to zero4 ,this is1 of course1 as it should be1 and it is not necessary to pay any attention to the tabulated feeds in facing operations4 ,setting the ,turret ,slide4--,the next adjustment is that of setting the turret slide4 ,in making this adjustment the turret is set in such relation to the work that the tools will have but a small amount of overhang1 the cam-shaft being revolved by hand until the cam-roll is at the extreme top of the forward feeding cam1 so that the turret slide is at the extreme of its forward movement4 ,when this adjustment has been made by the means provided1 set the turret index tripping dog so as to revolve the turret at the proper point4 ,after a turning tool-holder and tool is attached to the face of the turret1 cam ,no4 #a is placed in its operating position and is revolved by hand until the roll is on the point of the cam and the turret at the forward extreme of its motion4 ,at this point the tool-holder is set so that the cutter will be far enough forward to complete its turning operation4 ,the feed cam is then turned backward1 thus returning the turret slide1 and the cutter is set to turn the flange to the proper diameter for the roughing cut4 ,the turret slide is fed forward and back while the cutter is adjusted1 and when it is properly set1 the flange is turned1 the cam-drum being fed by hand4 ,this is the first trial cut on the piece4 ,a facing tool1 shown in the working position in ,fig4 #cf1 is placed at this station of the turret1 being held in the turret hole4 ,this tool has a pilot bar and a holder which contains a facing blade4 ,feeding by hand1 as before1 the tool is adjusted lengthwise so as to rough-face the work to the dimension desired4 ,in a similar way the finish-turning and facing tools for the second position of the turret are set1 the cam-shaft being revolved by hand to bring this second face and second cam into the working position4 7,the finish-facing tool is not shown in place in ,fig4 #cf47 ,illustration3 ,fig4 #ch4 ,diagram of ,cross-slide ,cams and ,feeding ,mechanism ,setting the ,cross-slide ,cam4--,as previously mentioned1 the third turret face has no tool1 the cutting off of the collar being done during this part of the cycle of operations4 ,it has been taken for granted that in setting the turret slide1 room has been left between it and the chuck for the cross-slide4 ,the cross-slide is clamped in a longitudinal position on the bed1 convenient for the cutting-off operation1 which is done with a tool ,d 7,fig4 #cf7 in the rear toolpost1 thus leaving the front unobstructed for the operator4 ,when both forming and cutting off are to be done1 the forming tool is generally held at the front and the cutting-off tool at the back because heavier and more accurate forming can be done with the work revolving downward toward a tool in the front toolpost1 than with the tool at the rear where it is subjected to a lifting action4 ,the arrangement of the cross-slide cams is shown in ,fig4 #ch1 which is an end view of the large drum ,e1 ,fig4 #cb4 ,the rear feed cam is the one to be used1 and since this cutting-off operation is a short one1 it may be done during the return of the turret for position ,no4 #c4 ,the cam drum is1 therefore1 rotated by hand until the turret face ,no4 #c has begun to return4 ,the cross-slide cams are then loosened and the rear feed cam is swung around to just touch the roller ,r which operates arm ,a1 the cross-slide having been adjusted out to nearly the limit of its forward travel1 leaving approximately enough movement for cutting off the collar4 ,the rear feed cam is then clamped in this position4 ,a cutting-off tool is next placed in the rear toolpost at the proper height4 ,the rear toolpost slide is then adjusted to bring the point of the cutting-off tool up to the work1 and the cam drum is revolved by hand until the piece is cut off4 ,the cross-slide tool is1 of course1 set in the proper position to make a collar of the required thickness4 ,feeding by hand is discontinued when the roll is on the point of the cam2 the cutting-off tool slide is then permanently set on the cross-slide so that the point of the cutting-off tool enters the bore just far enough to completely sever the collar from the bushing4 ,the motion of the cam drum is continued1 by hand1 until the roll is over the point of the feed cam4 ,the cross-slide is then pushed back1 by hand1 until the cam and roll are again in contact1 when the return cam is brought up and clamped in position1 so that there is just room for the roll between the feed cam and the return cam4 ,the rear return cam 7as the hand feed of the cam drum is continued7 brings the cross-slide back to its central position4 ,since there is no front tool used for this series of operations 7although a tool is shown in the front toolpost1 ,fig4 #cf71 the first feed and return cams are allowed to remain wherever they happen to be4 ,these cam adjustments can all be made from the front of the machine4 ,setting the ,boring ,tool for ,recessing4--,the feeding of the turret slide is now continued to make sure that the cutting-off tool is returned to its normal position before the facing tool in the next face of the turret begins to work4 ,the facing of the bushing1 so far as the setting of the tool is concerned1 is merely a repetition of the facing operation at the first position of the turret4 ,the recessing tool is next set4 ,this tool1 which is shown diagrammatically in ,fig4 #ci1 is very simple as compared with the somewhat complex operation it has to perform4 ,this recess is for clearance only1 and accurate dimensions and fine finish are not necessary4 ,the recessing tool consists simply of a slender boring-bar held in the turret and carrying a cutter suitably located about midway the bar4 ,the forward end of the bar is small enough to enter a bell-mouthed bushing held in the chuck4 ,the boring-bar is bent to one side far enough so that the cutter clears the hole as the bar enters1 but is forced into the work as the rounded hole of the bushing engages the end of the bar and deflects it into the working position4 ,the upper diagram shows the position of the bar as it enters the hole1 and the lower one the position after it has entered the bushing and is engaged in turning the recess4 ,this bar is set in the turret so that at the extreme forward travel of the turret slide1 the recess will be bored to the required length4 ,the cutter must also be adjusted to bore to the desired diameter4 ,this completes the setting of the cutting tools4 ,illustration3 ,fig4 #ci4 ,flexible ,boring ,tool used for ,recessing a ,bushing in ,automatic ,chucking and ,turning ,machine ,adjustments for ,automatic ,feed and ,speed ,changes4--,the machine must now be set to perform automatically the desired changes of spindle speed and the fast and slow cam movements for the tools4 ,after placing a new piece of work in the machine 7the first one having been completed in the setting-up operation71 the cam-shaft is revolved by hand until the turning tool in turret face ,no4 #a is just about to begin its cut4 ,the control wheel ,d1 ,fig4 #cd1 is rotated in its normal direction until the next graduation marked slow is in line with an index mark on the base of the machine4 ,then the nearest pin ,m is moved up until it bears against a tooth of the star wheel 7previously referred to7 and is clamped in this position4 ,the pin should now be in the proper location1 but to test its position1 rotate the cam shaft backward by hand and throw in the automatic feed2 then watch the cut to see if the drum slows down just before the tool begins to work4 ,if it does not1 the pin should be adjusted a little1 one way or the other1 as may be required4 7,in going over a piece of work for the first time1 it is best to have the feed set to the smallest rate1 feed change handle ,k being in position ,no4 #a47 ,after the cut has been completed and the turret feed cam-roll is on the high part of the cam1 the power feed should again be stopped and the handwheel revolved until the next graduation marked fast is opposite the index mark4 ,the next stop pin is then moved up until it just touches the star wheel1 where it is clamped in position4 ,the feed being again thrown in1 the turret will be returned rapidly1 indexed1 and moved forward for the second operation4 ,after stopping the automatic movement1 the pins are set for this face1 and so on for all the operations1 including that in which the cross-slide is used for cutting off the finished collar4 ,as the first1 second1 and third operations are on comparatively large diameters1 they should be done at the slow speed1 handle ,j1 ,fig4 #cd1 being set to give that speed4 ,while the turret slide is being returned between operations #c and #d1 one of the spindle speed-changing dogs ,n should be clamped to the rim of disk ,d so as to change the spindle speed to the fast movement4 ,this speed is continued until the last operation is completed1 when a second dog is clamped in place to again throw in the slow movement4 ,the feed knock-off dog should also be clamped in place on the disk to stop the machine at the completion of the fifth operation1 when the turret is in its rear position4 ,this completes the setting up of the machine4 ,if the feed is finer than is necessary1 the feed change handle ,k may now be moved to a position which will give the maximum feed that can be used4 ,it has taken considerable time to describe the setting up of the machine for this simple operation1 but in the hands of a competent man it can be done quite rapidly4 ,while a simple operation has been referred to in the foregoing1 it will be understood that a great variety of work can be done on a machine of this type4 ,it is not unusual to see as many as ten cutting tools operating simultaneously on a piece of work1 the tools being carried by the turret1 cross-slide and back facing attachment4 ,the latter is operated from a separate cam applied to the cam-shaft and acting through levers on a back facing bar which passes through a hole in the spindle4 ,in this back facing bar may be mounted drills1 cutters1 facing tools1 etc4 for machining the rear face of a casting held in the chuck jaws4 ,where extreme accuracy is required1 a double back facing attachment may be used1 arranged with cutters for taking both roughing and finishing cuts4 ,the use of this attachment often saves a second operation4 ,this automatic chucking and turning machine is also adapted for bar work1 especially in diameters varying from #c to #f inches4 ,turning ,flywheel in ,automatic ,chucking and ,turning ,machine4--,a typical operation on the ,potter ,johnston automatic chucking and turning machine is illustrated in ,fig4 #dj1 which shows the machine arranged for turning the cast-iron flywheel for the engine of a motor truck4 ,the rim is turned and faced on both sides and the hub is bored1 reamed and faced on both sides4 ,the flywheel casting is held in a chuck by three special jaws which grip the inside of the rim4 ,the order of the operations is as follows3 ,the rear end of the hub is faced by the back facing bar2 the cored hole is started by a four-lipped drill in the turret and the front end of the hub is rough-faced4 7,these tools are on the rear side of the turret when the latter is in the position shown in the illustration47 ,after the turret indexes1 the hole is rough-bored by tool ,a and while this is being done1 the outside of the rim is rough-turned by tool ,b held in a special bracket attached to the turret4 ,both sides of the rim are also rough-faced by tools ,c and ,d held at the front of the cross-slide1 this operation taking place at the same time that the rim is turned and the hole is being bored4 ,illustration3 ,fig4 #dj4 ,machining ,flywheels in ,potter ,johnston ,automatic ,chucking and ,turning ,machine ,the turret again automatically recedes and indexes1 thus locating bar ,e and turning tool ,g in the working position4 ,the hole is then finish-bored by tool ,e and the hub is finish-faced by blade ,f2 at the same time the rim is finish-turned by tool ,g and the sides are finish-faced to the proper width by two tools held at the rear of the cross-slide4 ,the turret automatically recedes and indexes a third time1 thus locating the flat-cutter reamer-bar ,h in the working position and then the hole is reamed to the required diameter4 ,this completes the cycle of operations4 ,the total time for machining this flywheel is forty minutes4 ,automatic ,multiple-spindle ,chucking ,machine4--,an example of the specialized machines now used for producing duplicate parts1 is shown in ,fig4 #da4 ,this is a ,new ,britain automatic multiple-spindle chucking machine of the single-head type and it is especially adapted for boring1 reaming and facing operations on castings or forgings which can readily be held in chuck jaws4 ,this particular machine has five spindles1 which carry and revolve the tools4 ,the work being machined is held stationary in the multiple chuck turret ,a which holds each part in line with one of the spindles and automatically indexes1 so that the work passes from one spindle to another until it is finished4 ,the turret then indexes the finished piece to a sixth or loading position which is not opposite a spindle1 where the part is removed and replaced with a rough casting4 ,each pair of chuck jaws is operated independently of the others by the use of a chuck wrench4 ,these jaws are made to suit the shape of the work4 ,illustration3 ,fig4 #da4 ,new ,britain ,multiple-spindle ,automatic ,chucking ,machine of ,single-head ,type ,when a single-head machine is in operation1 the turret advances and feeds the work against the revolving tools so that a number of pieces are operated upon at the same time4 ,the turret is fed by a cam drum ,b4 ,cam strips are bolted to the outside of this drum and act directly against a roller attached to the yoke ,c which can be clamped in different positions on the spindle ,d1 the position depending upon the length of the work4 ,on the opposite end of the turret spindle is the indexing mechanism ,e4 ,an automatically spring-operated latch ,f engages notches in the rim of the dividing wheel1 thus accurately locating the turret4 ,the turret is locked by a steadyrest ,g1 which1 for each working position1 automatically slides into engagement with one of the notches in the turret4 ,this relieves the indexing mechanism of all strain4 ,illustration3 ,fig4 #db4 ,detail ,view of ,new ,britain ,double-head ,eight-spindle ,machine1 ,boring1 ,reaming and ,facing ,castings ,this type of machine is also built with two spindle heads1 the double-head design being used for work requiring operations on both ends4 ,when the double-head machine is in operation1 the revolving spindles and tools advance on both sides of the chuck turret1 the latter remaining stationary except when indexing4 ,the feed drums on the double-head machine are located directly beneath each group of spindles4 ,fig4 #db shows an example of work on a machine of the double-head design4 ,this is an eight-spindle machine1 there being two groups of four spindles on each side of the turret4 ,the castings ,e are for the wheel hubs of automobiles4 ,the order of the operations on one of the castings1 as it indexes around1 is as follows3 ,the hole in the hub is first rough-reamed by taper reamer ,a and the opposite end of the hub is rough-faced and counterbored by a tool in spindle ,a#a4 ,when the turret indexes1 this same casting is reamed close to the finished size by reamer ,b and the left end of the hub is rough-faced by cutter ,f1 while a tool in the opposite spindle ,b#a finishes the counterboring and facing operation4 ,at the third position1 reamer ,c finishes the hole accurately to size1 and when the work is indexed to the fourth position1 the hub on the left side is finish-faced by a tool in spindle ,d4 7,the third and fourth spindles of the right-hand group are not used for this particular operation47 ,when the turret again indexes1 the finished casting is removed and replaced with a rough one4 ,while the successive operations on a single casting have just been described1 it will be understood that all of the tools operate simultaneously and that a finished casting arrives at the unloading and loading position each time the turret indexes4 ,three hundred of these malleable castings are machined in nine hours4 ,selecting ,type of ,turning ,machine4--,the variety of machine tools now in use is very extensive1 and as different types can often be employed for the same kind of work1 the selection of the best and most efficient machine is often a rather difficult problem4 ,to illustrate1 there are many different types and designs of turning machines1 such as the ordinary engine lathe1 the hand-operated turret lathe1 the semi-automatic turning machine1 and the fully automatic type1 which1 after it is set up and started1 is entirely independent4 ,hence1 when a certain part must be turned1 the question is1 what kind of machine should be used1 assuming that it would be possible to employ several different machines8 ,the answer to this question usually depends principally upon the number of parts that must be turned4 ,for example1 a certain casting or forging might be turned in a lathe1 which could be finished in some form of automatic or semi-automatic turning machine much more quickly4 ,it does not necessarily follow1 however1 that the automatic is the best machine to use1 because the lathe is designed for general work and the part referred to could doubtless be turned with the regular lathe equipment1 whereas the automatic machine would require special tools and it would also need to be carefully adjusted4 ,therefore1 if only a few parts were needed1 the lathe might be the best tool to use1 but if a large number were required1 the automatic or semi-automatic machine would doubtless be preferable1 because the saving in time effected by the latter type would more than offset the extra expense for tool equipment and setting the machine4 ,it is also necessary1 in connection with some work1 to consider the degree of accuracy required1 as well as the rate of production1 and it is because of these varying conditions that work of the same general class is often done in machines of different types1 in order to secure the most efficient results4 ,,chapter ,,vi ,,vertical ,,boring ,,mill ,,practice ,all the different types of turning machines now in use originated from the lathe4 ,many of these tools1 however1 do not resemble the lathe because1 in the process of evolution1 there have been many changes made in order to develop turning machines for handling certain classes of work to the best advantage4 ,the machine illustrated in ,fig4 #a belongs to the lathe family and is known as a vertical boring and turning mill4 ,this type1 as the name implies1 is used for boring and turning operations1 and it is very efficient for work within its range4 ,the part to be machined is held to the table ,b either by clamps or in chuck jaws attached to the table4 ,when the machine is in operation1 the table revolves and the turning or boring tools 7which are held in tool-blocks ,t7 remain stationary1 except for the feeding movement4 ,very often more than one tool is used at a time1 as will be shown later by examples of vertical boring mill work4 ,the tool-blocks ,t are inserted in tool-bars ,t#a carried by saddles ,s which are mounted on cross-rail ,c4 ,each tool-head 7consisting of a saddle and tool-bar7 can be moved horizontally along cross-rail ,c1 and the tool-bars ,t#a have a vertical movement4 ,these movements can be effected either by hand or power4 ,when a surface is being turned parallel to the work table1 the entire tool-head moves horizontally along the cross-rail1 but when a cylindrical surface is being turned1 the tool-bar moves vertically4 ,the tool-heads are moved horizontally by the screws ,h and ,h#a1 and the vertical feed for the tool-bars is obtained from the splined shafts ,v and ,v#a1 there being a separate screw and shaft for each head so that the feeding movements are independent4 ,these feed shafts are rotated for the power feed by vertical shafts ,a and ,a#a on each side of the machine4 ,these vertical shafts connect with the feed shafts through bevel and spur gears located at the ends of the cross-rail4 ,on most boring mills1 connection is made with one of the splined shafts ,v or screw ,h1 by a movable gear1 which is placed on whichever shaft will give the desired direction of feed4 ,the particular machine illustrated is so arranged that either the right or left screw or feed shaft can be engaged by simply shifting levers ,d#a or ,d4 ,illustration3 ,fig4 #a4 ,gisholt ,vertical ,boring and ,turning ,mill ,the amount of feed per revolution of the table is varied for each tool-head by feed-changing mechanisms ,f on each side of the machine4 ,these feed boxes contain gears of different sizes1 and by changing the combinations of these gears1 the amount of feed is varied4 ,five feed changes are obtained on this machine by shifting lever ,e1 and this number is doubled by shifting lever ,g4 ,by having two feed boxes1 the feeding movement of each head can be varied independently4 ,the direction of either the horizontal or vertical feed can be reversed by lever ,r1 which is also used for engaging or disengaging the feeds4 ,this machine is equipped with the dials ,i and ,i#a which can be set to automatically disengage the feed at any predetermined point4 ,there are also micrometer dials graduated to thousandths of an inch and used for adjusting the tools without the use of measuring instruments4 ,the work table ,b is driven indirectly from a belt pulley at the rear1 which transmits the power through gearing4 ,the speed of the table can be varied for turning large or small parts1 by levers ,j and ,k and the table can be started1 stopped or rotated part of a revolution by lever ,l which connects with a friction clutch4 ,there are corresponding feed and speed levers on the opposite side1 so that the machine can be controlled from either position4 ,the heads can be adjusted along the cross-rail for setting the tools by hand-cranks ,n1 and the tool slides can be moved vertically by turning shafts ,v with the same cranks4 ,with this machine1 however1 these adjustments do not have to be made by hand1 ordinarily1 as there are rapid power movements controlled by levers ,m4 ,these levers automatically disengage the feeds and enable the tool-heads to be rapidly shifted to the required position1 the direction of the movement depending upon the position of the feed reverse lever ,r and lever ,d4 ,this rapid traverse1 which is a feature applied to modern boring mills of medium and large size1 saves time and the labor connected with hand adjustments4 ,the cross-rail ,c has a vertical adjustment on the faces of the right and left housings which support it1 in order to locate the tool-heads at the right height for the work4 ,this adjustment is effected by power and is controlled by levers at the sides of the housings4 ,normally1 the cross-rail is bolted to the housings1 and these bolts must be loosened before making the adjustment1 and must always be tightened afterwards4 ,the function of these different levers has been explained to show1 in a general way1 how a vertical boring machine is operated4 ,it should be understood1 however1 that the arrangement differs considerably on machines of other makes4 ,the construction also varies considerably on machines of the same make but of different size4 ,illustration3 ,fig4 #b4 ,small ,boring and ,turning ,mill with ,single ,turret-head ,all modern vertical boring mills of medium and large sizes are equipped with two tool-heads1 as shown in ,fig4 #a1 because a great deal of work done on a machine of this type can have two surfaces machined simultaneously4 ,on the other hand1 small mills of the type illustrated in ,fig4 #b have a single head4 ,the toolslide of this machine1 instead of having a single tool-block1 carries a five-sided turret ,t in which different tools can be mounted4 ,these tools are shifted to the working position as they are needed1 by loosening binder lever ,l and turning or indexing the turret4 ,the turret is located and locked in any of its five positions by lever ,i1 which controls a plunger that engages notches at the rear4 ,frequently1 all the tools for machining a part can be held in the turret1 so that little time is required for changing from one tool to the next4 ,some large machines having two tool-heads are also equipped with a turret on one head4 ,boring and ,turning in a ,vertical ,boring ,mill4--,the vertical boring mill is1 in many respects1 like a lathe placed in a vertical position1 the table of the mill corresponding to the faceplate or chuck of the lathe and the tool-head to the lathe carriage4 ,much of the work done by a vertical mill could also be machined in a lathe1 but the former is much more efficient for work within its range4 ,to begin with1 it is more convenient to clamp work to a horizontal table than to the vertical surface of a lathe faceplate1 or1 as someone has aptly said1 ,it is easier to lay a piece down than to hang it up4 ,this is especially true of the heavy parts for which the boring mill is principally used4 ,very deep roughing cuts can also be taken with a vertical mill4 ,this type of machine mill is designed for turning and boring work which1 generally speaking1 is quite large in diameter in proportion to the width or height4 ,the work varies greatly1 especially in regard to its diameter1 so that boring mills are built in a large range of sizes4 ,the small and medium sizes will swing work varying from about #cj inches to #f or #g feet in diameter1 whereas large machines1 such as are used for turning very large flywheels1 sheaves1 etc41 have a swing of #af or #bj feet1 and larger sizes are used in some shops4 ,the size of a vertical mill1 like any other machine tool1 should be somewhat in proportion to the size of the work for which it is intended1 as a very large machine is unwieldy1 and1 therefore1 inefficient for machining comparatively small parts4 ,holding and ,setting ,work on ,boring ,mill ,table4--,there are three general methods of holding work to the table of a boring mill2 namely1 by the use of chucks1 by ordinary bolts and clamps1 or in special fixtures4 ,chucks which are built into the table 7as illustrated in ,fig4 #b7 and have both universal and independent adjustments for the jaws can be used to advantage for holding castings that are either round or irregular in shape4 ,the universal adjustment is used for cylindrical parts1 such as disks1 flywheels1 gear blanks1 etc41 and the independent adjustment1 for castings of irregular shape4 ,chucks which have either an independent or universal movement for the jaws are known as a combination type and usually have three jaws4 ,there is also a four-jaw type which has the independent adjustment only4 ,this style is preferable for work that is not cylindrical and which must be held very securely4 ,chuck jaws that do not form a part of the machine table1 but are bolted to it in the required position1 are also employed extensively1 especially on comparatively large machines4 ,most of the work done in a vertical mill is held in a chuck4 ,occasionally1 however1 it is preferable to clamp a part directly to the table4 ,this may be desirable because of the shape and size of the work1 or because it is necessary to hold a previously machined surface directly against the table in order to secure greater accuracy4 ,sometimes a casting is held in the chuck for turning one side1 and then the finished side is clamped against the table for turning the opposite side4 ,parts which are to be machined in large quantities are often held in special fixtures4 ,this method is employed when it enables the work to be set up more quickly than would be possible if regular clamps or chuck jaws were used4 ,work that is to be turned or bored should first be set so that the part to be machined is about central with the table4 ,for example1 the rim of a flywheel should be set to run true so that it can be finished by removing about the same amount of metal around the entire rim2 in other words1 the rim should be set concentric with the table1 as shown in ,fig4 #c1 and the sides of the rim should also be parallel to the table4 ,illustration3 ,fig4 #c4 ,plan ,view showing ,flywheel ,casting ,chucked for ,turning ,a simple tool that is very useful for testing the position of any cylindrical casting consists of a wooden shank into which is inserted a piece of wire1 having one end bent4 ,this tool is clamped in the toolpost and as the work revolves the wire is adjusted close to the cylindrical surface being tested4 ,the movement of the work with relation to the stationary wire point will1 of course1 show whether or not the part runs true4 ,the advantage of using a piece of wire for testing1 instead of a rigid tool1 is that the wire1 owing to its flexibility1 will simply be bent backward if it is moved too close to a surface which is considerably out of true4 ,the upper surface of a casting can be tested for parallelism with the table by using this same wire gage1 or by comparing the surface1 as the table is revolved slowly1 with a tool held in the toolpost4 ,an ordinary surface gage is also used for this purpose4 ,the proper surface to set true1 in any case1 depends upon the requirements4 ,a plain cylindrical disk would be set so that the outside ran true and the top surface was parallel with the table4 ,when setting a flywheel1 if the inside of the rim is to remain rough1 the casting should be set by this surface rather than by the outside1 so that the rim1 when finished1 will be uniform in thickness4 ,as far as possible1 chucks should be used for holding cylindrical parts1 owing to their convenience4 ,the jaws should be set against an interior cylindrical surface whenever this is feasible4 ,to illustrate1 the flywheel in ,fig4 #c is gripped by the inside of the rim which permits the outside to be turned at this setting of the work4 ,it is also advisable to set a flywheel casting in the chuck so that a spoke rests against one of the jaws as at d1 if this is possible4 ,this jaw will then act as a driver and prevent the casting from slipping or turning in the chuck jaws1 owing to the tangential pressure of the turning tool4 ,when a cut is being taken1 the table and work rotate as shown by arrow a1 and the thrust of the cut 7taken by tool t7 tends to move the wheel backward against the direction of rotation1 as shown by arrow b4 ,if one of the chuck jaws bears against one of the spokes1 this movement is prevented4 ,it is not always feasible to use a chuck jaw as a driver and then a special driver having the form of a small angle-plate or block is sometimes bolted directly to the table4 ,another method of driving is to set a brace between a spoke or projection on the work and a chuck jaw or strip attached to the table4 ,drivers are not only used when turning flywheels1 but in connection with any large casting1 especially when heavy cuts have to be taken4 ,of course1 some castings are so shaped that drivers cannot be employed4 ,turning in a ,boring ,mill4--,the vertical type of boring mill is used more for turning cylindrical surfaces than for actual boring1 although a large part of the work requires both turning and boring4 ,we shall first consider1 in a general way1 how surfaces are turned and then refer to some boring operations4 ,the diagram ,a1 ,fig4 #d1 illustrates how a horizontal surface would be turned4 ,the tool t is clamped in tool-block t#a1 in a vertical position1 and it is fed horizontally as the table and work rotate4 ,the tool is first adjusted by hand for the proper depth of cut and the automatic horizontal feed is then engaged4 ,when a cylindrical surface is to be turned1 the tool 7provided a straight tool is used7 is clamped in a horizontal position and is fed downward as indicated at ,b4 ,the amount that the tool should feed per revolution of the work1 depends upon the kind of material being turned1 the diameter of the turned part and the depth of the cut4 ,illustration3 ,fig4 #d4 7,a7 ,turning a ,flat ,surface4 7,b7 ,turning a ,cylindrical ,surface ,most of the parts machined in a vertical boring mill are made of cast iron and1 ordinarily1 at least one roughing and one finishing cut is taken4 ,the number of roughing cuts required in any case depends1 of course1 upon the amount of metal to be removed4 ,an ordinary roughing cut in soft cast iron might vary in depth from #a_/h or #c_/af inch to #c_/h or #a_/b inch and the tool would probably have a feed per revolution of from #a_/af to #a_/h inch1 although deeper cuts and coarser feeds are sometimes taken4 ,these figures are merely given to show1 in a general way1 what cuts and feeds are practicable4 ,the tool used for roughing usually has a rounded end which leaves a ridged or rough surface4 ,to obtain a smooth finish1 broad flat tools are used4 ,the flat cutting edge is set parallel to the tool's travel and a coarse feed is used in order to reduce the time required for taking the cut4 ,the finishing feeds for cast iron vary from #a_/d to #c_/d inch on ordinary work4 ,the different tools used on the vertical mill will be referred to more in detail later4 ,all medium and large sized vertical boring mills are equipped with two tool-heads and two tools are frequently used at the same time1 especially on large work4 ,fig4 #i illustrates the use of two tools simultaneously4 ,the casting shown is a flywheel1 and the tool on the right side turns the upper side of the rim1 while the tool on the left side turns the outside or cylindrical surface4 ,as a boring mill table rotates in a counter-clockwise direction1 the left-hand tool is reversed to bring the cutting edge at the rear4 ,by turning two surfaces at once1 the total time for machining the casting is1 of course1 greatly reduced4 ,the turning of flywheels is a common vertical boring mill operation1 and this work will be referred to in detail later on4 ,illustration3 ,fig4 #e4 ,tools for ,boring and ,reaming ,holes ,boring ,operations4--,there are several methods of machining holes when using a vertical boring mill4 ,ordinarily1 small holes are cored in castings and it is simply necessary to finish the rough surface to the required diameter4 ,some of the tools used for boring and finishing comparatively small holes are shown in ,fig4 #e4 ,sketch ,a shows a boring tool consisting of a cutter c inserted in a shank1 which1 in turn1 is held in the tool slide1 or in a turret attached to the tool slide4 ,with a tool of this type1 a hole is bored by taking one or more cuts down through it4 ,the tool shown at ,b is a four-lipped drill which is used for drilling cored holes preparatory to finishing by a cutter or reamer4 ,this drill would probably finish a hole to within about #a_/cb inch of the finish diameter1 thus leaving a small amount of metal for the reamer to remove4 ,the tool illustrated at ,c has a double-ended flat cutter c1 which cuts on both sides4 ,these cutters are often made in sets for boring duplicate parts4 ,ordinarily1 there are two cutters in a set1 one being used for roughing and the other for finishing4 ,the cutter passes through a rectangular slot in the bar and this particular style is centrally located by shoulders s1 and is held by a taper pin p4 ,some cutter bars have an extension end1 or pilot as it is called1 which passes through a close-fitting bushing in the table to steady the bar4 ,sketch ,d shows a finishing reamer4 ,this tool takes a very light cut and is intended to finish holes that have been previously bored close to the required size4 ,sometimes a flat cutter ,c is used for roughing and a reamer for finishing4 ,the reamer is especially desirable for interchangeable work1 when all holes must have a smooth finish and be of the same diameter4 ,when a reamer is held rigidly to a turret or toolslide1 it is liable to produce a hole that is either tapering or larger than the reamer diameter4 ,to prevent this1 the reamer should be held in a floating holder which1 by means of a slight adjustment1 allows the reamer to align itself with the hole4 ,there are several methods of securing this floating movement4 7,see ,floating ,reamer ,holders47 ,illustration3 ,fig4 #f4 ,boring with ,regular ,turning ,tools ,large holes or interior cylindrical surfaces are bored by tools held in the regular tool-head4 ,the tool is sometimes clamped in a horizontal position as shown at ,a1 ,fig4 #f1 or a bent type is used as at ,b4 ,cast iron is usually finished by a broad flat tool as at ,c1 the same as when turning exterior surfaces4 ,obviously a hole that is bored in this way must be large enough to admit the tool-block4 ,illustration3 ,fig4 #g4 ,set of ,boring ,mill ,tools ,turning ,tools for the ,vertical ,boring ,mill4--,a set of turning tools for the vertical boring mill is shown in ,fig4 #g4 ,these tools can be used for a wide variety of ordinary turning operations4 ,when a great many duplicate parts are to be machined1 special tool equipment can often be used to advantage1 but as the form of this equipment depends upon the character of the work1 only standard tools have been shown in this illustration4 ,the tool shown at ,a is a right-hand1 roughing tool1 and a left-hand tool of the same type is shown at ,b4 ,tool ,c is an offset or bent1 left-hand round nose for roughing1 and ,d is a right-hand offset roughing tool4 ,a straight round nose is shown at ,e4 ,tool ,f has a flat1 broad cutting edge and is used for finishing4 ,left-and right-hand finishing tools of the offset type are shown at ,g and ,h1 respectively4 ,tool ,i has a square end and is used for cutting grooves4 ,right-and left-hand parting tools are shown at ,j and ,k1 and tool ,l is a form frequently used for rounding corners4 ,illustration3 ,fig4 #h4 ,diagrams ,illustrating ,use of ,different ,forms of ,tools ,the diagrams in ,fig4 #h show1 in a general way1 how each of the tools illustrated in ,fig4 #g are used1 and corresponding tools are marked by the same reference letters in both of these illustrations4 ,the right-and left-hand roughing tools ,a and ,b are especially adapted for taking deep roughing cuts4 ,one feeds away from the center of the table1 or to the right 7when held in the right-hand tool-block7 and the other tool is ground to feed in the opposite direction4 ,ordinarily1 when turning plain flat surfaces1 the cut is started at the outside and the tool feeds toward the center1 as at ,b1 although it is sometimes more convenient to feed in the opposite direction1 as at ,a1 especially when there is a rim or other projecting part at the outside edge4 ,the tool shown at ,a could also be used for turning cylindrical surfaces1 by clamping it in a horizontal position across the bottom of the tool-block4 ,the feeding movement would then be downward or at right-angles to the work table4 ,the offset round-nose tools ,c and ,d are for turning exterior or interior cylinder surfaces4 ,the shank of this tool is clamped in the tool-block in a vertical position and as the bent end extends below the tool-block1 it can be fed down close to a shoulder4 ,the straight type shown at ,e is commonly used for turning steel or iron1 and when the point is drawn out narrower1 it is also used for brass1 although the front is then ground without slope4 ,tool ,f is for light finishing cuts and broad feeds4 ,the amount of feed per revolution of the work should always be less than the width of the cutting edge as otherwise ridges will be left on the turned surface4 ,the offset tools ,g and ,h are for finishing exterior and interior cylindrical surfaces4 ,these tools also have both vertical and horizontal cutting edges and are sometimes used for first finishing a cylindrical and then a horizontal surface1 or vice versa4 ,tool ,i is adapted to such work as cutting packing-ring grooves in engine pistons1 forming square or rectangular grooves1 and similar work4 ,the parting tools ,j and ,k can also be used for forming narrow grooves or for cutting off rings1 etc4 ,the sketch ,k 7,fig4 #h7 indicates how a tool of this kind might be used for squaring a corner under a shoulder4 ,tool ,l is frequently used on boring mills for rounding the corners of flywheel rims1 in order to give them a more finished appearance4 ,it has two cutting edges so that either side can be used as when rounding the inner and outer corners of a rim4 ,the turning tools of a vertical boring mill are similar1 in many respects1 to those used in a lathe1 although the shanks of the former are shorter and more stocky than those of lathe tools4 ,the cutting edges of some of the tools also differ somewhat in form1 but the principles which govern the grinding of lathe and boring mill tools are identical1 and those who are not familiar with tool grinding are referred to ,chapter ,,ii1 in which this subject is treated4 ,turning a ,flywheel on a ,vertical ,mill4--,the turning of a flywheel is a good example of the kind of work for which a vertical boring mill is adapted4 ,a flywheel should preferably be machined on a double-head mill so that one side and the periphery of the rim can be turned at the same time4 ,a common method of holding a flywheel is shown in ,fig4 #i4 ,the rim is gripped by four chuck jaws ,d which1 if practicable1 should be on the inside where they will not interfere with the movement of the tool4 ,two of the jaws1 in this case1 are set against the spokes on opposite sides of the wheel1 to act as drivers and prevent any backward shifting of work when a heavy cut is being taken4 ,the illustration shows the tool to the right rough turning the side of the rim1 while the left-hand tool turns the periphery4 ,finishing cuts are also taken over the rim1 at this setting1 and the hub is turned on the outside1 faced on top1 and the hole bored4 ,illustration3 ,fig4 #i4 ,turning the ,rim of a ,flywheel ,the three tools ,a1 ,b and ,c1 for finishing the hole1 are mounted in the turret4 ,bar ,a1 which carries a cutter at its end1 first rough bores the hole4 ,the sizing cutter ,b is then used to straighten it before inserting the finishing reamer ,c4 ,fig4 #aj shows the turret moved over to a central position and the sizing cutter ,b set for boring4 ,the head is centrally located 7on this particular machine7 by a positive center-stop4 ,the turret is indexed for bringing the different tools into the working position1 by loosening the clamping lever ,l and pulling down lever ,i which disengages the turret lock-pin4 ,when all the flywheels in a lot have been machined as described1 the opposite side is finished4 ,illustration3 ,fig4 #aj4 ,tool ,b set for ,boring the ,hub ,illustration3 ,fig4 #aa4 ,diagrams showing ,method of ,turning and ,boring a ,flywheel on a ,double-head ,mill having one ,turret ,head ,in order to show more clearly the method of handling work of this class1 the machining of a flywheel will be explained more in detail in connection with ,fig4 #aa1 which illustrates practically the same equipment as is shown in ,figs4 #i and #aj4 ,the successive order in which the various operations are performed is as follows3 ,tool a 7see sketch ,a7 rough turns the side of the rim1 while tool b1 which is set with its cutting edge toward the rear1 rough turns the outside4 ,the direction of the feeding movement for each tool is indicated by the arrows4 ,when tool a has crossed the rim1 it is moved over for facing the hub1 as shown by the dotted lines4 ,the side and periphery of the rim are next finished by the broad-nose finishing tools c and d 7see sketch ,b74 ,the feed should be increased for finishing1 so that each tool will have a movement of say #a_/d or #c_/h inch per revolution of the work1 and the cuts should1 at least1 be deep enough to remove the marks made by the roughing tools4 ,tool c is also used for finishing the hub as indicated by the dotted lines4 ,after these cuts are taken1 the outside of the hub and inner surface of the rim are usually turned down as far as the spokes1 by using offset tools similar to the ones shown at ,c and ,d in ,fig4 #g4 ,the corners of the rim and hub are also rounded to give the work a more finished appearance1 by using a tool ,l4 ,the next operation is that of finishing the hole through the hub4 ,the hard scale is first removed by a roughing cutter r 7sketch ,c71 which is followed by a sizing cutter s4 ,the hole is then finished smooth and to the right diameter by reamer f4 ,the bars carrying cutters r and s have extensions or pilots which enter a close-fitting bushing in the table1 in order to steady the bar and hold it in alignment4 ,when the hole is finished1 the wheel is turned over1 so that the lower side of the rim and hub can be faced4 ,the method of holding the casting for the final operation is shown at ,d4 ,the chuck jaws are removed1 and the finished side of the rim is clamped against parallels p resting on the table4 ,the wheel is centrally located for turning this side by a plug e which is inserted in a hole in the table and fits the bore of the hub4 ,the wheel is held by clamps which bear against the spokes4 ,roughing and finishing cuts are next taken over the top surface of the rim and hub and the corners are rounded1 which completes the machining operations4 ,if the rim needs to be a certain width1 about the same amount of metal should be removed from each side1 unless sandy spots or blow-holes in the casting make it necessary to take more from one side than from the other4 ,that side of the rim which was up in the mold when the casting was made should be turned first1 because the porous1 spongy spots usually form on the cope or top side of a casting4 ,convex ,turning ,attachment for ,boring ,mills4--,fig4 #ab shows a vertical boring mill arranged for turning pulleys having convex rims2 that is1 the rim1 instead of being cylindrical1 is rounded somewhat so that it slopes from the center toward either side4 7,the reason for turning a pulley rim convex is to prevent the belt from running off at one side1 as it sometimes tends to do when a cylindrical pulley is used47 ,the convex surface is produced by a special attachment which causes the turning tool to gradually move outward as it feeds down1 until the center of the rim is reached1 after which the movement is inward4 ,illustration3 ,fig4 #ab4 ,gisholt ,mill equipped with ,convex ,turning ,attachment ,the particular attachment shown in ,fig4 #ab consists of a special box-shaped tool-head ,f containing a sliding holder ,g1 in which the tool is clamped by set-screws passing through elongated slots in the front of the tool-head4 ,in addition1 there is a radius link ,l which swivels on a stud at the rear of the tool-head and is attached to vertical link ,h4 ,link ,l is so connected to the sliding tool-block that any downward movement of the tool-bar ,i causes the tool to move outward until the link is in a horizontal position1 after which the movement is reversed4 ,when the attachment is first set up1 the turning tool is placed at the center of the rim and then link ,l is clamped to the vertical link while in a horizontal position4 ,the cut is started at the top edge of the rim1 and the tool is fed downward by power1 the same as when turning a cylindrical surface4 ,the amount of curvature or convexity of a rim can be varied by inserting the clamp bolt ,j in different holes in link ,l4 ,illustration3 ,fig4 #ac4 ,turning a ,taper or ,conical ,surface ,the tools for machining the hub and sides of the rim are held in a turret mounted on the left-hand head1 as shown4 ,the special tool-holder ,a contains two bent tools for turning the upper and lower edges of the pulley rim at the same time as the tool-head is fed horizontally4 ,roughing and finishing tools ,b are for facing the hub1 and the tools ,c1 ,d1 and ,e rough bore1 finish bore1 and ream the hole for the shaft4 ,turning ,taper or ,conical ,surfaces4--,conical or taper surfaces are turned in a vertical boring mill by swiveling the tool-bar to the proper angle as shown in ,fig4 #ac4 ,when the taper is given in degrees1 the tool-bar can be set by graduations on the edge of the circular base ,b1 which show the angle a to which the bar is swiveled from a vertical position4 ,the base turns on a central stud and is secured to the saddle ,s by the bolts shown1 which should be tightened after the tool-bar is set4 ,the vertical power feed can be used for taper turning the same as for cylindrical work4 ,illustration3 ,fig4 #ad4 ,turning a ,conical ,surface by using the ,combined ,vertical and ,horizontal ,feeds ,occasionally it is necessary to machine a conical surface which has such a large included angle that the tool-bar cannot be swiveled far enough around to permit turning by the method illustrated in ,fig4 #ac4 ,another method1 which is sometimes resorted to for work of this class1 is to use the combined vertical and horizontal feeds4 ,suppose we want to turn the conical casting ,w 7,fig4 #ad71 to an angle of #cj degrees1 as shown1 and that the tool-head of the boring mill moves horizontally #a_/d inch per turn of the feed-screw and has a vertical movement of #c_/af inch per turn of the upper feed-shaft4 ,if the two feeds are used simultaneously1 the tool will move a distance h of say #h inches1 while it moves downward a distance v of #f inches1 thus turning the surface to an angle y4 ,this angle is greater 7as measured from a horizontal plane7 than the angle required1 but1 if the tool-bar is swiveled to an angle x1 the tool1 as it moves downward1 will also be advanced horizontally1 in addition to the regular horizontal movement4 ,the result is that the angle y is diminished and if the tool-bar is set over the right amount1 the conical surface can be turned to an angle a of #cj degrees4 ,the problem1 then1 is to determine what the angle x should be for turning to a given angle a4 ,illustration3 ,fig4 #ae4 ,diagram showing ,method of ,obtaining ,angular ,position of ,tool-head when ,turning ,conical ,surfaces by using ,vertical and ,horizontal ,feeding ,movements ,the way angle x is calculated will be explained in connection with the enlarged diagram1 ,fig4 #ae1 which shows one-half of the casting4 ,the sine of the known angle a is first found in a table of natural sines4 ,then the sine of angle b1 between the taper surface and center-line of the tool-head1 is determined as follows3 sinb 7sina x h7 _/ v1 in which h represents the rate of horizontal feed and v the rate of vertical feed4 ,the angle corresponding to sine b is next found in a table of sines4 ,we now have angles b and a1 and by subtracting the sum of these angles from #ij degrees1 the desired angle x is obtained4 ,to illustrate3 ,the sine of #cj degrees is #j4e2 then sin b 7#j4e x #a_/d7 _/ #c_/af #j4ffff2 hence angle b #da degrees #di minutes1 and x #ij deg4-7#cj deg4 #da deg4 #di'7 #ah degrees #aa minutes4 ,hence to turn the casting to angle a in a boring mill having the horizontal and vertical feeds given1 the tool-head would be set over from the vertical #ah degrees and #aa minutes which is equivalent to about #ah-a_/f degrees4 ,if the required angle a were greater than angle y obtained from the combined feeds with the tool-bar in a vertical position1 it would then be necessary to swing the lower end of the bar to the left rather than to the right of a vertical plane4 ,when the required angle a exceeds angle y1 the sum of angles a and b is greater than #ij degrees so that angle x for the tool-head 7a b7 - #ij degrees4 ,turret-lathe ,type of ,vertical ,boring ,mill4--,the machine illustrated in ,fig4 #af was designed to combine the advantages of the horizontal turret lathe and the vertical boring mill4 ,it is known as a vertical turret lathe1 but resembles1 in many respects1 a vertical boring mill4 ,this machine has a turret on the cross-rail the same as many vertical boring mills1 and1 in addition1 a side-head ,s4 ,the side-head has a vertical feeding movement1 and the tool-bar ,t can be fed horizontally4 ,the tool-bar is also equipped with a four-sided turret for holding turning tools4 ,this arrangement of the tool-heads makes it possible to use two tools simultaneously upon comparatively small work4 ,when both heads are mounted on the cross-rail1 as with a double-head boring mill1 it is often impossible to machine certain parts to advantage1 because one head interferes with the other4 ,the drive to the table 7for the particular machine illustrated7 is from a belt pulley at the rear1 and fifteen speed changes are available4 ,five changes are obtained by turning the pilot-wheel ,a and this series of five speeds is compounded three times by turning lever ,b4 ,each spoke of pilot-wheel ,a indicates a speed which is engaged only when the spoke is in a vertical position1 and the three positions for ,b are indicated1 by slots in the disk shown4 ,the number of table revolutions per minute for different positions of pilot-wheel ,a and lever ,b are shown by figures seen through whichever slot is at ,c4 ,there are five rows of figures corresponding to the five spokes of the pilot-wheel and three figures in a row1 and the speed is shown by arrows on the sides of the slots4 ,the segment disk containing these figures also serves as an interlocking device which prevents moving more than one speed controlling lever at a time1 in order to avoid damaging the driving mechanism4 ,illustration3 ,fig4 #af4 ,bullard ,vertical ,turret ,lathe ,the feeding movement for each head is independent4 ,lever ,d controls the engagement or disengagement of the vertical or cross feeds for the head on the cross-rail4 ,the feed for the side-head is controlled by lever ,e4 ,when this lever is pushed inward1 the entire head feeds vertically1 but when it is pulled out1 the tool-bar feeds horizontally4 ,these two feeds can be disengaged by placing the lever in a neutral position4 ,the direction of the feeding movement for either head can be reversed by lever ,r4 ,the amount of feed is varied by feed-wheel ,f and clutch-rod ,g4 ,when lever ,e is in the neutral position1 the side-head or tool-bar can be adjusted by the hand-cranks ,h and ,i1 respectively4 ,the cross-rail head and its turret slide have rapid power traverse movements for making quick adjustments4 ,this rapid traverse is controlled by the key-handles ,j4 ,the feed-screws for the vertical head have micrometer dials ,k for making accurate adjustments4 ,there are also large dials at ,l which indicate vertical movements of the side head and horizontal movements of the tool slide4 ,all of these dials have small adjustable clips c which are numbered to correspond to numbers on the faces of the respective turrets4 ,these clips or observation stops are used in the production of duplicate parts4 ,for example1 suppose a tool in face ,no4 #a for the main turret is set for a given diameter and height of shoulder on a part which is to be duplicated4 ,to obtain the same setting of the tools for the next piece1 clips ,no4 #a1 on both the vertical feed rod and screw dials1 are placed opposite the graduations which are intersected by stationary pointers secured to the cross-rail4 ,the clips are set in this way after the first part has been machined to the required size and before disturbing the final position of the tools4 ,for turning a duplicate part1 the tools are simply brought to the same position by turning the feed screws until the clips and stationary pointers again coincide4 ,for setting tools on other faces of either turret1 this operation is repeated1 except that clips are used bearing numbers corresponding to the turret face in use4 ,the main turret of this machine has five holes in which are inserted the necessary boring and turning tools1 drills or reamers1 as may be required4 ,by having all the tools mounted in the turret1 they can be quickly and accurately set in the working position4 ,when the turret is indexed from one face to the next1 binder lever ,n is first loosened4 ,the turret then moves forward1 away from its seat1 thus disengaging the indexing and registering pins which accurately locate it in any one of the five positions4 ,the turret is revolved by turning crank ,m1 one turn of this handle moving the turret #a_/e revolution or from one hole to the next4 ,the side-head turret is turned by loosening lever ,o4 ,the turret slide can be locked rigidly in any position by lever ,p and its saddle is clamped to the cross-rail by lever ,q4 ,the binder levers for the saddle and toolslide of the side-head are located at ,u and ,v1 respectively4 ,a slide that does not require feeding movements is locked in order to obtain greater rigidity4 ,to illustrate1 if the main tool slide were to feed vertically and not horizontally1 it might be advisable to lock the saddle to the cross-rail1 while taking the vertical cut4 ,illustration3 ,fig4 #ag4 ,turning a ,gear ,blank on a ,vertical ,turret ,lathe ,the vertical slide can be set at an angle for taper turning1 and the turret is accurately located over the center of the table for boring or reaming1 by a positive center stop4 ,the machine is provided with a brake for stopping the work table quickly1 which is operated by lifting the shaft of pilot-wheel ,a4 ,the side-and cross-rails are a unit and are adjusted together to accommodate work of different heights4 ,this adjustment is effected by power on the particular machine illustrated1 and it is controlled by a lever near the left end of the cross-rail4 ,before making this adjustment1 all binder bolts which normally hold the rails rigidly to the machine column must be released1 and care should be taken to tighten them after the adjustment is made4 ,illustration3 ,fig4 #ah4 ,turning ,gasoline ,engine ,flywheel on ,vertical ,turret ,lathe--,first ,position ,examples of ,vertical ,turret ,lathe ,work4--,in order to illustrate how a vertical turret lathe is used1 one or two examples of work will be referred to in detail4 ,these examples also indicate1 in a general way1 the class of work for which this type of machine is adapted4 ,fig4 #ag shows how a cast-iron gear blank is machined4 ,the work is gripped on the inside of the rim by three chuck jaws1 and all of the tools required for the various operations are mounted in the main and side turrets4 ,the illustration shows the first operation which is that of rough turning the hub1 the top side of the blank and its periphery4 ,the tools ,a for facing the hub and upper surface are both held in one tool-block on the main turret1 and tool ,a#a for roughing the periphery is in the side turret4 ,with this arrangement1 the three surfaces can be turned simultaneously4 ,illustration3 ,fig4 #ai4 ,turning ,gasoline ,engine ,flywheel--,second ,position ,illustration3 ,fig4 #bj4 ,diagrams showing ,how ,successive ,operations are ,performed by ,different ,tools in the ,turret ,the main turret is next indexed one-sixth of a revolution which brings the broad finishing tools ,b into position1 and the side turret is also turned to locate finishing tool ,b#a at the front4 7,the indexing of the main turret on this particular machine is effected by loosening binder lever n and raising the turret lock-pin by means of lever p47 ,the hub1 side and periphery of the blank are then finished4 ,when tools ,b are clamped in the tool-blocks1 they are1 of course1 set for turning the hub to the required height4 ,the third operation is performed by the tools at ,c1 one of which breaks or chamfers the corner of the cored hole in the hub1 to provide a starting surface for drill ,d1 and the other turns the outside of the hub1 after the chamfering tool is removed4 ,the four-lipped shell-drill ,d is next used to drill the cored hole and then this hole is bored close to the finished size and concentric with the circumference of the blank by boring tool ,e1 which is followed by the finishing reamer ,f4 ,when the drill1 boring tool and reamer are being used1 the turret is set over the center or axis of the table1 by means of a positive center stop on the left-side of the turret saddle4 ,if it is necessary to move the turret beyond the central position1 this stop can be swung out of the way4 ,figs4 #ah and #ai illustrate the turning of an automobile flywheel1 which is another typical example of work for a machine of this type4 ,the flywheel is finished in two settings4 ,its position for the first series of operations is shown in ,fig4 #ah1 and the successive order of the four operations for the first setting is shown by the diagrams1 ,fig4 #bj4 ,the first operation requires four tools which act simultaneously4 ,the three held in tool-block ,a of the turret1 face the hub1 the web and the rim of the flywheel1 while tool a in the side-head rough turns the outside diameter4 ,the outside diameter is also finished by broad-nosed tool b which is given a coarse feed4 ,in the second operation1 the under face of the rim is finished by tool c1 the outer corners are rounded by tool d and the inner surface of the rim is rough turned by a bent tool ,b1 which is moved into position by indexing the main turret4 ,in the third operation1 the side-head is moved out of the way and the inside of the rim is finished by another bent tool ,b#a4 ,the final operation at this setting is the boring of the central hole1 which is done with a bar ,c having interchangeable cutters which make it possible to finish the hole at one setting of the turret4 ,the remaining operations are performed on the opposite side of the work which is held in soft jaws ,j accurately bored to fit the finished outside diameter as indicated in ,fig4 #ai4 ,the tool in the main turret turns the inside of the rim1 and the side-head is equipped with two tools for facing the web and hub simultaneously4 ,as the tool in the main turret operates on the left side of the rim1 it is set with the cutting edge toward the rear4 ,in order to move the turret to this position1 which is beyond the center of the table1 the center stop previously referred to is swung out of the way4 ,floating ,reamer ,holders4--,if a reamer is held rigidly in the turret of a boring mill or turret lathe1 it is liable to produce a hole which tapers slightly or is too large4 ,when a hole is bored with a single-point boring tool1 it is concentric with the axis of rotation1 and if a reamer that is aligned exactly with the bored hole is fed into the work1 the finished hole should be cylindrical and the correct size4 ,it is very difficult1 however1 to locate a reamer exactly in line with a bored hole1 because of slight variations in the indexing of the turret1 or errors resulting from wear of the guiding ways or other important parts of the machine4 ,to prevent inaccuracies due to this cause1 reamers are often held in what is known as a floating holder4 ,this type of holder is so arranged that the reamer1 instead of being held rigidly1 is allowed a slight free or floating movement so that it can follow a hole which has been bored true1 without restraint4 ,in this way the hole is reamed straight and to practically the same size as the reamer4 ,illustration3 ,fig4 #ba4 ,two ,types of ,floating ,reamer ,holders ,there are many different designs of floating holders but the general principle upon which they are based is illustrated by the two types shown in ,fig4 #ba4 ,the reamer and holder shown to the left has a ball-shank ,a which bears against a backing-up screw ,b inserted in the end of holder ,c through which the driving pin passes4 ,the lower end of the reamer shank is also spherical-shaped at ,d1 and screw-pin ,e secures the shell reamer to this end4 ,it will be noted that the hole in the shank for pin ,e is bell-mouthed on each side of the center and that there is clearance at ,f between the shank and reamer shell2 hence the reamer has a free floating action in any direction4 ,this holder has given very satisfactory results4 ,illustration3 ,fig4 #bb4 ,multiple-spindle ,cylinder ,boring ,machine ,the holder shown to the right is attached to the face of the turret by four fillister-head screws4 ,sleeve ,c is held in plate ,a by means of two steel pins ,b which are tight in plate ,a and made to fit freely in bayonet grooves ,d4 ,reamer holder ,e floats on sleeve ,c1 the floating motion being obtained through the four steel pins ,g extending into driving ring ,f4 ,two of the pins are tight in the holder ,e and two in sleeve ,c4 ,the faces of sleeve ,c1 driving ring ,f1 and reamer holder ,e are held tightly against each other by means of spring ,h which insures the reamer being held perfectly true4 ,spring ,h is adjusted by means of nut ,i which is turned with a spanner wrench furnished with each holder4 ,the reamer is so held that its axis is always maintained parallel to the center of the hole1 and1 at the same time1 it has a slight self-adjusting tendency radially1 so that the hole and reamer will automatically keep in perfect alignment with each other4 ,multiple ,cylinder ,boring ,machine4--,in automobile and other factories where a great many gasoline engine cylinders are required1 multiple-spindle boring machines of the vertical type are commonly used4 ,the machine shown in ,fig4 #bb is a special design for boring four cylinders which are cast en bloc or in one solid casting4 ,the work is held in a box jig which has a top plate equipped with guide bearings for holding the spindles rigidly while boring4 ,the lower end of each spindle has attached to it a cutter-head and the boring is done by feeding the table and casting vertically4 ,this feeding movement is effected by power and it is disengaged automatically when the cutters have bored to the required depth4 ,the particular machine illustrated is used for rough boring only1 the cylinders being finished by reaming in another similar machine4 ,the cylinders are bored to a diameter of #c-e_/h inches1 and about #c_/h inch of metal is removed by the roughing cut4 ,the spindles have fixed center-to-center distances as the machine is intended for constant use on cylinders of one size1 so that adjustment is not necessary4 ,of course1 a special machine of this kind is only used in shops where large numbers of cylinders of one design are required continually4 ,some cylinder boring machines of the vertical type have spindles which can be adjusted for different center-to-center distances if this should be necessary in order to accommodate a cylinder of another size4 ,,chapter ,,vii ,,horizontal ,,boring ,,machines ,a boring machine of the horizontal type is shown in ,fig4 #a4 ,the construction and operation of this machine is very different from that of a vertical boring mill and it is also used for an entirely different class of work4 ,the horizontal machine is employed principally for boring1 drilling or milling1 whereas the vertical design is especially adapted to turning and boring4 ,the horizontal type is also used for turning or facing flanges or similar surfaces when such an operation can be performed to advantage in connection with other machine work on the same part4 ,the type of machine illustrated in ,fig4 #a has a heavy base or bed to which is bolted the column ,c having vertical ways on which the spindle-head ,h is mounted4 ,this head contains a sleeve or quill in which the spindle ,s slides longitudinally4 ,the spindle carries cutters for boring1 whereas milling cutters or the auxiliary facing arm are bolted to the end ,a of the spindle sleeve4 ,the work itself is attached either directly or indirectly to the table or platen ,p4 ,when the machine is in operation1 the cutter or tool revolves with the spindle sleeve or spindle and either the cutter or the part being machined is given a feeding movement1 depending on the character of the work4 ,the spindle can be moved in or out by hand for adjustment1 or by power for feeding the cutter1 as when boring or drilling4 ,illustration3 ,fig4 #a4 ,lucas ,horizontal ,boring1 ,drilling and ,milling ,machine ,the entire spindle-head ,h can also be moved vertically on the face of the column ,c1 by hand1 for setting the spindle to the proper height1 or by power for feeding a milling cutter in a vertical direction4 ,when the vertical position of the spindle-head is changed1 the outboard bearing block ,b also moves up or down a corresponding amount1 the two parts being connected by shafts and gearing4 ,block ,b steadies the outer end of the boring-bar and the back-rest in which this block is mounted can be shifted along the bed to suit the length of the work1 by turning the squared end of shaft ,d with a crank4 ,the platen ,p has a cross-feed1 and the saddle ,e on which it is mounted can be traversed lengthwise on the bed2 both of these movements can also be effected by hand or power4 ,there is a series of power feeding movements for the cutters and1 in addition1 rapid power movements in a reverse direction from the feed for returning a cutter quickly to its starting position1 when this is desirable4 ,this machine is driven by a belt connecting pulley ,g with an overhead shaft4 ,when the machine is in operation1 this pulley is engaged with the main driving shaft by a friction clutch ,f controlled by lever ,l4 ,this main shaft drives through gearing a vertical shaft ,i1 which by means of other gears in the spindle-head imparts a rotary movement to the spindle4 ,as a machine of this type is used for boring holes of various diameters and for a variety of other work1 it is necessary to have a number of speed changes for the spindle4 ,nine speeds are obtained by changing the position of the sliding gears controlled by levers ,r and this number is doubled by back-gears in the spindle-head and controlled by lever ,j4 ,the amount of feed for the spindle1 spindle-head1 platen or saddle is varied by two levers ,k and ,k#a which control the position of sliding gears through which the feeding movements are transmitted4 ,the direction of the feed can be reversed by shifting lever ,o4 ,with this particular machine1 nine feed changes are available for each position of the spindle back-gears1 making a total of eighteen changes4 ,the feeding movement is transmitted to the spindle-head1 spindle1 platen or saddle1 as required1 by the three distributing levers ,t1 ,u and ,v1 which control clutches connecting with the transmission shafts or feed screws4 ,when lever ,t is turned to the left1 the longitudinal power feed for the spindle is engaged1 whereas turning it to the right throws in the vertical feed for the spindle-head4 ,lever ,u engages the cross-feed for platen ,p and lever ,v1 the longitudinal feed for saddle ,e4 ,these levers have a simple but ingenious interlocking device which makes it impossible to engage more than one feed at a time4 ,for example1 if lever ,t is set for feeding the spindle1 levers ,u and ,v are locked against movement4 ,the feeds are started and stopped by lever ,m which also engages the rapid power traverse when thrown in the opposite direction4 ,this rapid traverse operates for whatever feed is engaged by the distributing levers and1 as before stated1 in a reverse direction4 ,for example1 if the reverse lever ,o is set for feeding the spindle to the right1 the rapid traverse would be to the left1 and vice versa4 ,the cross-feed for the platen can be automatically tripped at any point by setting an adjustable stop in the proper position and the feed can also be tripped by a hand lever at the side of the platen4 ,all the different feeding movements can be effected by hand as well as by power4 ,by means of handwheel ,n1 the spindle can be moved in or out slowly1 for feeding a cutter by hand4 ,when the friction clamp ,q is loosened1 the turnstile ,w can be used for traversing the spindle1 in case a hand adjustment is desirable4 ,the spindle-head can be adjusted vertically by turning squared shaft ,x with a crank1 and the saddle can be shifted along the bed by turning shaft ,y4 ,the hand adjustment of the platen is effected by shaft ,z4 ,the spindle-head1 platen and saddle can also be adjusted from the end of the machine1 when this is more convenient4 ,shafts ,x1 ,y and ,z are equipped with micrometer dials which are graduated to show movements of one-thousandth inch4 ,these dials are used for accurately adjusting the spindle or work and for boring holes or milling surfaces that must be an exact distance apart4 ,horizontal ,boring ,machine with ,vertical ,table ,adjustment4--,another horizontal boring machine is partly shown in ,fig4 #b4 ,this machine is of the same type as that illustrated in ,fig4 #a1 but its construction is quite different1 as will be seen4 ,the spindle cannot be adjusted vertically as with the first design described1 but it is mounted and driven very much like the spindle of a lathe1 and adjustment for height is obtained by raising or lowering the work table4 ,the design is just the reverse1 in this respect1 of the machine shown in ,fig4 #a1 which has a vertical adjustment for the spindle1 and a work table that remains in the same horizontal plane4 ,the raising or lowering of the table is effected by shaft ,e1 which rotates large nuts engaging the screws ,s4 ,shaft ,e is turned either by hand or power4 ,illustration3 ,fig4 #b4 ,horizontal ,boring and ,drilling ,machine with ,vertical ,table ,adjustment ,the main spindle is driven by a cone pulley ,p1 either directly1 or indirectly through the back-gears shown4 ,this arrangement gives six spindle speeds1 and double this number is obtained by using a two-speed countershaft overhead4 ,the motion for feeding the spindle longitudinally is transmitted through a cone of gears1 which gives the required changes1 to a pinion meshing with a rack which traverses the spindle4 ,the large handwheel ,h and a corresponding wheel on the opposite side are used for adjusting the spindle rapidly by hand4 ,the yoke or outboard bearing ,b for the boring-bars can be clamped in any position along the bed for supporting the bar as close to the work as possible4 ,horizontal boring machines are built in many other designs1 but they all have the same general arrangement as the machines illustrated and operate on the same principle1 with the exception of special types intended for handling certain classes of work exclusively4 ,the horizontal boring1 drilling and milling machine is very efficient for certain classes of work because it enables all the machining operations on some parts to be completed at one setting4 ,to illustrate1 a casting which requires drilling1 boring and milling at different places1 can often be finished without disturbing its position on the platen after it is clamped in place4 ,frequently a comparatively small surface needs to be milled after a part has been bored4 ,if this milling operation can be performed while the work is set up for boring1 accurate results will be obtained 7provided the machine is in good condition7 and the time saved that would otherwise be required for re-setting the part on another machine4 ,some examples of work on which different operations are performed at the same setting will be referred to later4 ,the horizontal boring machine also makes it possible to machine duplicate parts without the use of jigs1 which is important1 especially on large work1 owing to the cost of jigs4 ,drilling and ,boring--,cutters ,used4--,holes are drilled in a horizontal machine by simply inserting a drill of required size either directly in the spindle ,s 7see ,fig4 #a71 or in a reducing socket1 and then feeding the spindle outward either by hand or power4 ,when a hole is to be bored1 a boring-bar ,b#a is inserted in the spindle and the cutter is attached to this bar4 ,the latter is then fed through the hole as the cutter revolves4 ,the distinction made by machinists between drilling and boring is as follows3 ,a hole is said to be drilled when it is formed by sinking a drill into solid metal1 whereas boring means the enlargement of a drilled or cored hole either by the use of a single boring tool1 a double-ended cutter which operates on both sides of the hole1 or a cutter-head having several tools4 ,there are various methods of attaching cutters to boring-bars and the cutters used vary for different classes of work4 ,a simple style of cutter which is used widely for boring small holes is shown at ,a in ,fig4 #c4 ,the cutter c is made from flat stock and the cutting is done by the front edges e and e#a1 which are beveled in opposite directions4 ,the cutter is held in the bar by a taper wedge w and it is centered by shoulders at s1 so that the diameter of the hole will equal the length across the cutter4 ,the outer corners at the front should be slightly rounded1 as a sharp corner would be dulled quickly4 ,these cutters are made in different sizes and also in sets for roughing and finishing4 ,the roughing cutter bores holes to within about #a_/cb inch of the finish size and it is then replaced by the finishing cutter4 ,a cutter having rounded ends1 as shown by the detail sketch a1 is sometimes used for light finishing cuts4 ,these rounded ends form the cutting edges and give a smooth finish4 ,illustration3 ,fig4 #c4 ,boring-cutters of ,different ,types ,another method of holding a flat cutter is shown at ,b4 ,the conical end of a screw bears against a conical seat in1 the cutter1 thus binding the latter in its slot4 ,the conical seat also centers the cutter4 ,a very simple and inexpensive form of cutter is shown at ,c4 ,this is made from a piece of round steel1 and it is held in the bar by a taper pin which bears against a circular recess in the side of the cutter4 ,this form has the advantage of only requiring a hole through the boring-bar1 whereas it is necessary to cut a rectangular slot for the flat cutter4 ,illustration3 ,fig4 #d4 ,boring with a ,flat ,double-ended ,cutter ,fig4 #d shows how a hole is bored by cutters of the type referred to4 ,the bar rotates as indicated by the arrow a and at the same time feeds longitudinally as shown by arrow b4 ,the speed of rotation depends upon the diameter of the hole and the kind of material being bored1 and the feed per revolution must also be varied to suit conditions4 ,no definite rule can be given for speed or feed4 ,on some classes of work a long boring-bar is used1 which passes through the hole to be bored and is steadied at its outer end by the back-rest ,b1 ,figs1 #a and #b4 ,on other work1 a short bar is inserted in the spindle having a cutter at the outer end4 ,an inexpensive method of holding a cutter at the end of a bar is shown at ,d1 ,fig4 #c4 ,the cutter passes through a slot and is clamped by a bolt as shown4 ,when it is necessary to bore holes that are blind or closed at the bottom1 a long boring-bar which passes through the work cannot1 of course1 be used4 ,sometimes it is necessary to have a cutter mounted at the extreme end of a bar in order to bore close to a shoulder or the bottom of a hole4 ,one method of holding a cutter so that it projects beyond the end of a bar is indicated at ,e4 ,a screw similar to the one shown at ,b is used1 and the conical end bears in a conical hole in the cutter4 ,this hole should be slightly offset so that the cutter will be forced back against its seat4 ,the tool shown at ,f has adjustable cutters4 ,the inner end of each cutter is tapering and bears against a conical-headed screw b which gives the required outward adjustment4 ,the cutters are held against the central bolt by fillister-head screws f and they are clamped by the screws c4 ,boring tools are made in many different designs and the number and form of the cutters is varied somewhat for different kinds of work4 ,illustration3 ,fig4 #e4 ,cutter-heads for ,boring ,large ,holes ,cutter-heads for ,boring ,large ,holes4--,when large holes are to be bored1 the cutters are usually held in a cast-iron head which is mounted on the boring-bar4 ,one type of cutter-head is shown in ,fig4 #e4 ,this particular head is double-ended and carries two cutters c4 ,the cutter-head is bored to fit the bar closely and it is prevented from turning by a key against which a set-screw is tightened4 ,by referring to the end view1 it will be seen that each cutter is offset with relation to the center of the bar1 in order to locate the front of the tool on a radial line4 ,the number of cutters used in a cutter-head varies4 ,by having several cutters1 the work of removing a given amount of metal in boring is distributed1 and holes can be bored more quickly with a multiple cutter-head1 although more power is required to drive the boring-bar4 ,the boring-bar is also steadied by a multiple cutter-head1 because the tendency of any one cutter to deflect the bar is counteracted by the cutters on the opposite side4 ,a disk-shaped head having four cutters is illustrated in ,fig4 #f4 ,the cutters are inserted in slots or grooves in the face of the disk and they are held by slotted clamping posts4 ,the shape of these posts is shown by the sectional view4 ,the tool passes through an elongated slot and it is tightly clamped against the disk by tightening nut n4 ,this head is also driven by a key which engages a keyway in the boring-bar4 ,illustration3 ,fig4 #f4 ,cutter-head with ,four ,boring ,tools ,two other designs of cutter-heads are shown in ,fig4 #g4 ,the one illustrated at ,a has three equally spaced cutters which are held in an inclined position4 ,the cutters are clamped by screws c and they can be adjusted within certain limits by screws s4 ,the cutters are placed at an angle so that they will extend beyond the front of the head1 thus permitting the latter to be moved up close to a shoulder4 ,the cutter-heads shown in ,figs4 #e and #f can also be moved up close to a shoulder if bent cutters are used as shown in the right-hand view1 ,fig4 #e4 ,the idea in bending the cutters is to bring the cutting edges in advance of the clamping posts so that they will reach a shoulder before the binding posts strike it4 ,the arrangement of cutter-head ,b 7,fig4 #g7 is clearly shown by the illustration4 ,cutter-heads are often provided with two sets of cutters1 one set being used for roughing and the other for finishing4 ,it is a good plan to make these cutters so that the ends e 7,fig4 #f7 will rest against the bar or bottom of the slot1 when the cutting edge is set to the required radius4 ,the cutters can then be easily set for boring duplicate work4 ,one method of making cutters in sets is to clamp the annealed stock in the cutter-head and then turn the ends to the required radius by placing the head in the lathe4 ,after both sets of cutters have been turned in this way1 they are ground to shape and then hardened4 ,illustration3 ,fig4 #g4 ,cutter-heads equipped with ,adjustable ,tools ,boring cutters intended for roughing and finishing cuts are shown in the detail view ,fig4 #h at ,a and ,b1 respectively4 ,the side of the roughing cutter ,a is ground to a slight angle c to provide clearance for the cutting edge1 and the front has a backward slope s to give the tool keenness4 ,this tool is a good form to use for roughing cuts in cast iron4 ,the finishing tool at ,b has a broad flat edge e and it is intended for coarse feeds and light cuts in cast iron4 ,if a round cutting edge is used for finishing1 a comparatively fine feed is required in order to obtain a smooth surface4 ,the corners of tool ,b are rounded and they should be ground to slope inward as shown in the plan view4 ,the top or ends d of both of these tools are backed off slightly to provide clearance4 ,this clearance should be just enough to prevent the surface back of the cutting edge from dragging over the work4 ,excessive end clearance not only weakens the cutting edge1 but tends to cause chattering4 ,as a finishing tool cuts on the upper end instead of on the side1 the front should slope backward as shown in the side view1 rather than sidewise as with a roughing cutter4 ,the angle of the slope should be somewhat greater for steel than cast iron1 unless the steel is quite hard1 thus requiring a strong blunt tool4 ,illustration3 ,fig4 #h4 ,boring ,tools for ,roughing and ,finishing ,cuts ,cylinder ,boring4--,fig4 #i illustrates the use of a cutter-head for cylinder boring4 ,after the cylinder casting is set on the platen of the machine1 the boring-bar with the cutter-head mounted on it is inserted in the spindle4 ,the bar ,b has a taper shank and a driving tang similar to a drill shank1 which fits a taper hole in the end of the spindle4 ,the cutter-head ,c is fastened to the bar so that it will be in the position shown when the spindle is shifted to the right1 as the feeding movement 7with this particular machine7 is to be in the opposite direction4 ,the casting ,a should be set central with the bar by adjusting the work-table vertically and laterally1 if necessary1 and the outer support ,f should be moved close to the work1 to make the bar as rigid as possible4 ,the cylinder is now ready to be bored4 ,ordinarily1 one or two roughing cuts and one finishing cut would be sufficient1 unless the rough bore were considerably below the finish diameter4 ,as previously explained1 the speed and feed must be governed by the kind of material being bored and the diameter of the cut4 ,the power and rigidity of the boring machine and the quality of the steel used for making the cutters also affect the cutting speed and feed4 ,as the finishing cut is very light1 a tool having a flat cutting edge set parallel to the bar is ordinarily used when boring cast iron4 ,the coarse feed enables the cut to be taken in a comparatively short time and the broad-nosed tool gives a smooth finish if properly ground4 ,illustration3 ,fig4 #i4 ,cylinder mounted on ,horizontal ,machine for ,boring ,the coarse finishing feed is not always practicable1 especially if the boring machine is in poor condition1 owing to the chattering of the tool1 which results in a rough surface4 ,the last or finishing cut should invariably be a continuous one1 for if the machine is stopped before the cut is completed1 there will be a ridge in the bore at the point where the tool temporarily left off cutting4 ,this ridge is caused by the cooling and resulting contraction and shortening of the tool during the time that it is stationary4 ,for this reason independent drives are desirable for boring machines4 ,facing arms are attached to the bar on either side of the cylinder for facing the flanges after the boring operation4 ,the turning tool of a facing arm is fastened to a slide which is fed outward a short distance each revolution1 by a star-wheel that is caused to turn as it strikes against a stationary pin4 ,by facing the flanges in this way1 they are finished square with the bore4 ,when setting a cylinder which is to be bored it should1 when the design will permit1 be set true by the outside of the flange1 or what is even better1 by the outside of the cylinder itself1 rather than by the rough bore1 in order that the walls of the finished cylinder will have a uniform thickness4 ,the position of very large cylinders1 while they are being bored1 is an important consideration4 ,such cylinders should be bored in the position which they will subsequently occupy when assembled4 ,for example1 the cylinder for a large horizontal engine should be bored while in a horizontal position1 as the bore is liable to spring to a slight oval shape when the cylinder is placed horizontal after being bored while standing in a vertical position4 ,if1 however1 the cylinder is bored while in the position in which it will be placed in the assembled engine1 this trouble is practically eliminated4 ,there is a difference of opinion among machinists as to the proper shape of the cutting point of a boring tool for finishing cuts1 some contending that a wide cutting edge is to be preferred1 while others advocate the use of a comparatively narrow edge with a reduced feed4 ,it is claimed1 that the narrow tool produces a more perfect bore1 as it is not so easily affected by hard spots in the iron1 and it is also pointed out that the minute ridges left by the narrow tool are an advantage rather than a disadvantage1 as they form pockets for oil and aid in lubricating the cylinder4 ,it is the modern practice1 however1 to use a broad tool and a coarse feed for the light finishing cut1 provided the tool does not chatter4 ,the type of machine tool used for boring cylinders1 and also the method of procedure is determined largely by the size of the work and the quantity which is to be machined4 ,the turret lathe1 as well as horizontal and vertical boring mills1 is used for this work1 and in automobile factories or other shops where a great many cylinders are bored1 special machines and fixtures are often employed4 ,illustration3 ,fig4 #aj4 ,boring a ,duplex ,cylinder on a ,horizontal ,machine ,boring a ,duplex ,gasoline ,engine ,cylinder4--,the method of holding work on a horizontal boring machine depends on its shape4 ,a cylinder or other casting having a flat base can be clamped directly to the platen1 but pieces of irregular shape are usually held in special fixtures4 ,fig4 #aj shows how the cylinder casting of a gasoline engine is set up for the boring operation4 ,the casting ,w is placed in a fixture ,f which is clamped to the machine table4 ,one end of the casting rests on the adjustable screws ,s and it is clamped by set-screws located in the top and sides of the fixture4 ,there are two cylinders cast integral and these are bored by a short stiff bar mounted in the end of the spindle and having cutters at the outer end4 ,a long bar of the type which passes through the work and is supported by the outboard bearing ,b1 could not be used for this work1 because the top of each cylinder is closed4 ,when one cylinder is finished the other is set in line with the spindle by adjusting the work-table laterally4 ,this adjustment is effected by screw ,c1 and the required center-to-center distance between the two cylinders can be gaged by the micrometer dial ,m on the cross-feed screw1 although positive stops are often used in preference4 ,after the first cylinder is bored1 the dial is set to the zero position by loosening the small knurled screw shown1 and turning the dial around4 ,the feed screw is then rotated until the dial shows that the required lateral adjustment is made1 which locates the casting for boring the second cylinder4 ,the end of the casting is also faced true by a milling cutter4 ,ordinarily1 milling cutters are bolted directly to the spindle sleeve ,a on this particular machine1 which gives a rigid support for the cutter and a powerful drive4 ,illustration3 ,fig4 #aa4 ,cylinder turned around for ,machining ,valve ,seats ,the next operation is that of boring and milling the opposite end of the cylinder4 ,this end is turned toward the spindle 7as shown in ,fig4 #aa7 without unclamping the work or fixture1 by simply turning the circular table ,t half way around4 ,this table is an attachment which is clamped to the main table for holding work that must be turned to different positions for machining the various parts4 ,its position is easily changed1 and as the work remains fixed with relation to the table1 the alignment between different holes or surfaces is assured1 if the table is turned the right amount4 ,in this case1 the casting needs to be rotated one-half a revolution or #ahj degrees1 and this is done by means of angular graduations on the base of the table4 ,the illustration shows the casting set for boring the inlet and exhaust valve chambers4 ,the different cutters required for boring are mounted on one bar as shown1 and the casting is adjusted crosswise to bring each valve chamber in position1 by using the micrometer dial4 ,the single-ended cutter c forms a shallow circular recess or seat in the raised pad which surrounds the opening4 ,the cover joint directly back of the cylinders is finished by milling4 ,illustration3 ,fig4 #ab4 ,boring ,differential ,gear ,casing ,examples of ,boring1 ,radial ,facing and ,milling4--,another example of boring1 in which the circular table is used1 is shown in ,fig4 #ab4 ,the work ,w is a casing for the differential gears of an automobile4 ,it is mounted in a fixture ,f which is bolted to the table4 ,the casting has round ends1 which are clamped in ,v-blocks1 thus aligning the work4 ,this fixture has a guide-bushing ,g which is centered with the bar and cutter in order to properly locate the casting4 ,there is a bearing at each end of the casing1 and two larger ones in the center4 ,these are bored by flat cutters similar to the style illustrated at ,a in ,fig4 #c4 ,the cutter for the inner bearings is shown at c4 ,illustration3 ,fig4 #ac4 ,facing and ,turning ,flange of ,differential ,gear ,casing ,after the bearings are bored1 the circular table is turned #ij degrees and the work is moved closer to the spindle 7as shown in ,fig4 #ac7 for facing flange ,f at right angles to the bearings4 ,circular flanges of this kind are faced in a horizontal boring machine by a special facing-arm or head ,h4 ,for this particular job this head is clamped directly to the spindle sleeve1 but it can also be clamped to the spindle if necessary4 ,the turning tool is held in a slotted toolpost1 and it is fed radially for turning the side or face of the flange1 by the well-known star feed at ,s4 ,when this feed is in operation the bent finger ,e is turned downward so that it strikes one of the star wheel arms for each revolution2 this turns the wheel slightly1 and the movement is transmitted to the tool-block by a feed-screw4 ,the illustration shows the tool set for turning the outside or periphery of the flange4 ,this is done by setting the tool to the proper radius and then feeding the work horizontally by shifting the work-table along the bed4 ,by referring to ,fig4 #ab it will be seen that the facing head does not need to be removed for boring1 as it is attached to the spindle driving quill and does not interfere with the longitudinal adjustment of the spindle4 ,this facing head is also used frequently for truing the flanges of cylinders which are to be bored1 and for similar work4 ,illustration3 ,fig4 #ad4 ,example of ,work requiring ,boring and ,milling ,fig4 #ad shows another example of work which requires boring and milling4 ,this casting is mounted on a fixture which is bolted to the main table4 ,in this case the circular table is not necessary1 because the work can be finished without swiveling it around4 ,after the boring is completed the edge ,e is trued by the large-face milling cutter ,m bolted to the spindle sleeve4 ,the irregular outline of the edge is followed by moving the table crosswise and the spindle vertically1 as required4 ,fixture for ,cylinder ,lining or ,bushing4--,a method of holding a cylinder lining or bushing while it is being bored is shown in ,fig4 #ae4 ,the lining ,l is mounted in two cast-iron ring-shaped fixtures ,f4 ,these fixtures are circular in shape and have flat bases which are bolted to the table of the machine4 ,on the inside of each fixture1 there are four equally spaced wedges ,w which fit into grooves as shown in the end view4 ,these wedges are drawn in against the work by bolts1 and they prevent the lining from rotating when a cut is being taken4 ,this form of fixture is especially adapted for holding thin bronze linings1 such as are used in pump cylinders1 because only a light pressure against the wedges is required1 and thin work can be held without distorting it4 ,if a very thin lining is being bored1 it is well to loosen the wedges slightly before taking the finishing cut1 so that the work can spring back to its normal shape4 ,illustration3 ,fig4 #ae4 ,cylinder ,lining mounted in ,fixture for ,boring ,illustration3 ,fig4 #af4 ,detrick ,harvey ,horizontal ,boring ,machine of the ,floor ,type ,boring ,engine ,bed ,casting ,horizontal ,boring ,machine of ,floor ,type4--,the type of horizontal boring1 drilling and milling machine1 shown in ,fig4 #af1 is intended for boring heavy parts such as the cylinders of large engines or pumps1 the bearings of heavy machine beds and similar work4 ,this machine can also be used for drilling and milling1 although it is intended primarily for boring1 and the other operations are usually secondary4 ,this design is ordinarily referred to as the floor type1 because the work-table is low for accommodating large heavy castings4 ,the spindle ,s which drives the boring-bar1 and the spindle feeding mechanism1 are carried by a saddle4 ,this saddle is free to move vertically on the face of column ,c which is mounted on transverse ways extending across the right-hand end of the main bed4 ,this construction permits the spindle to move vertically or laterally 7by traversing the column7 either for adjusting it to the required position or for milling operations4 ,the spindle also has a longitudinal movement for boring4 ,there is an outer bearing ,b for supporting the boring-bar1 which also has lateral and vertical adjustments1 so that it can be aligned with the bar4 ,the work done on a machine of this type is either clamped directly to the large bed-plate ,a 7which has a number of ,t-slots for receiving the heads of the clamping bolts7 or1 in some cases1 a special fixture may be used or an auxiliary table4 ,boring machines of this same general construction are built in many different sizes4 ,the main spindle of the machine illustrated is driven by a motor located at the rear of the vertical column ,c1 the motion being transmitted to the spindle through shafts and gearing4 ,the casting ,d1 shown in this particular illustration1 is for a steam engine of the horizontal type1 and the operation is that of boring the cylindrical guides or bearings for the crosshead4 ,these bearings have a diameter of #ae-c_/d inches and are #cg-c_/d inches long4 ,in boring them1 two roughing cuts and one finishing cut are taken4 ,the end of the casting1 which in the assembled engine bears against the cylinder1 is then faced by means of a regular facing arm4 ,after removing the boring-bar the table ,e of the special fixture on which the casting is mounted is turned one quarter of a revolution4 ,a large milling cutter #bd inches in diameter is next mounted on the spindle of the machine1 and one side of the main bearing1 as well as the pads for the valve-rod guide-bar brackets1 are milled4 ,the table is then revolved and the opposite side of the main bearing is milled in the same way1 the table being accurately located in the different positions by an index plunger ,f which engages holes on the under side4 ,the spindle is now moved upward to allow the table to be turned so as to locate the bearing end of the frame next to the headstock of the machine4 ,the milling cutter is then used to machine the inside and top surfaces of the main bearing4 ,by turning the fixture and not changing the position of the casting after it is bolted into place1 the various surfaces are machined in the correct relation to one another without difficulty4 ,this is a good example of the work done on horizontal boring machines of the floor type4 ,,index ,,page ,acme flat turret lathe1 examples of chuck work #bai ,acme standard thread and tool for cutting #aei ,acme standard thread gage #aeg ,acme thread tool1 measuring width with vernier caliper #aeg1 #aeh ,accumulation of errors #aje1 #ajf ,aligning lathe centers for cylindrical turning #af ,allowances1 average1 for forced fits #acj for different classes of fits #aca for driving fits #aca for forced fits of given pressure #acc for push fits #aca for running fits #aca for shrinkage fits #acc ,aluminum1 lubricant for machining #ec shape of tools for turning #ec speed and feed for machining #ec ,angle-plate applied to lathe faceplate #dh ,angles1 gage for accurate measurement of #ig ,apron of lathe #d1 #e ,arbor or mandrel press #bb ,arbors or mandrels for lathe work1 types of #ai use of #ag ,attachment1 application of ,hendey relieving #abe convex turning for vertical boring mill #bei for coarse threading in lathe #afj for spherical turning #aac for taper turning in lathe #hh ,hendey relieving #abc ,automatic chucking and turning machine1 ,potter ,johnston #bbc ,potter ,johnston1 method of setting-up #bbg ,potter ,johnston1 turning flywheel in #bcf ,back-gears of lathe #c1 #d ,bardons ,oliver turret lathe1 general description #agh ,bored holes1 measuring diameter of #da ,boring and reaming tools for vertical mill #bea ,boring and turning mill1 vertical1 general description #bdb vertical1 holding and setting work #bdg vertical1 turning in #bdi ,boring and turning mill1 vertical1 turning tools for #bec ,boring-bar cutters and methods of holding #bhj ,boring cutters for roughing and finishing cuts #bhe ,boring cylinders on horizontal machine #bhf ,boring holes to given center distance in lathe #ea ,boring in lathe1 example of #ci ,boring large castings in lathe #di ,boring large holes1 cutter-heads used for #bhc ,boring machine1 horizontal #bge horizontal1 examples of work on #bhi-big horizontal1 floor type #bid vertical1 multiple-spindle type #bgd ,boring tool1 lathe #dj ,box-tools1 different designs and examples of work #aic for general turret lathe work #aij ,bradford belt-driven lathe1 general description #a ,bradford quick change-gear type of lathe #agc ,brass1 speed for turning #eb tool for turning in lathe #eb ,bridle or hold-back for lathe #bf1 #bg ,bullard vertical turret lathe #bfd examples of work #bfh ,button method of locating work #aja ,caliper tool for taper turning #he ,calipers1 methods of setting #aj1 #aa ,cat-head1 application in lathe work #be ,center holes1 incorrect and correct forms #cb ,center indicator1 use of #ajj ,centered stock1 methods of facing ends #cd ,centers1 lathe1 aligning for cylindrical turning #af lathe1 grinder for truing #cd ,centering machine #cj ,centering parts to be turned #bh ,centering1 precaution for tool steel #cc ,change gears1 calculating for thread cutting #afg compound1 for thread cutting #agj for cutting fractional threads #aga for cutting metric pitches #aga for thread cutting #ace ,chasing dial for catching threads when screw cutting #ada ,chuck1 inaccuracy from pressure of jaws #db lathe1 application of #cg setting work in #db universal1 independent and combination #cf ,chucking and turning machine1 ,potter ,johnston automatic #bbc ,potter ,johnston automatic1 method of setting-up #bbg ,potter ,johnston automatic1 turning flywheel in #bcf ,chucking machine1 ,new ,britain1 multiple-spindle type #bch ,clearance angle for turning tools #ff ,clearance of turning tools1 meaning of #fb1 #fc ,coarse threading attachment for lathe #afj ,collapsing tap1 ,geometric #bjb ,combination chuck for lathe #cf ,compound rest1 applied to screw or thread cutting #adc applied to taper turning #ie ,convex turning attachment for vertical boring mills #bei ,copper1 tool for turning in lathe #eb ,crankshaft lathe1 description of ,r4 ,k4 ,le,blond special #ajh operation of ,r4 ,k4 ,le,blond #aaj ,crankshaft turning in engine lathe #ajg ,cross-slide stop for threading #aee ,cuts1 average depth for turning #ge roughing and finishing in lathe #ab1 #ge1 #gf ,cutter-heads1 for boring1 equipped with adjustable tools #bhd1 #bhe for horizontal boring machine #bhc ,cutters1 boring1 roughing and finishing types #bhe for boring-bars #bhj ,cutting lubricants for turning tools #gg ,cutting speeds1 average for turning #gb based on ,taylor's experiments #ga effect of lubricant on #gf factors which limit speeds for turning #gb rules for calculating #gd ,cylinder boring machine1 multiple-spindle type #bgd ,cylinder boring on horizontal machine #bhf ,cylinder lining1 fixture for holding when boring #bic ,cylindrical turning1 simple example of #f ,davis turret lathe1 turning bevel gear blanks #bab turning worm-gear blanks #baa ,depth of cut for turning1 average #ge ,detrick ,harvey horizontal boring machine1 floor type #bid ,dial for catching threads when screw cutting #ada ,dial gage1 testing concentricity of button with #ajc1 #ajd ,die and tap holders1 releasing #aii ,die-heads1 self-opening type #bjj ,disk gage1 for angles and tapers #ig rules for setting #ih1 #ii ,dogs or drivers1 lathe1 application of #af ,drill1 flat1 for lathe #dd ,drilling and reaming in lathe #dc ,drivers or dogs1 lathe1 application of #af ,driving fits1 allowances for #aca ,eccentric turning in lathe #ajf ,engine lathe1 general description #a ,errors1 accumulation of #aje1 #ajf ,faceplate1 indexing for multiple-thread cutting #aec lathe1 application of angle-plate to #dh lathe1 holding work on #de ,facing ends of centered stock1 different methods #cd ,feed and depth of cut for turning1 average #ge ,feeds and speeds for turning based on ,taylor's experiments #ga ,filing and polishing in lathe #ac ,finishing and roughing cuts in lathe #ge1 #gf ,fits1 allowances for different classes #aca different classes used in machine construction #abi driving1 allowances for #aca forced1 allowances for given pressure #acc forced1 average allowance for #acj forced1 pressure for #acb push1 allowances for #aca running1 allowances for #aca shrinkage1 allowances for #acc ,fixture for holding thin lining when boring #bic ,flat drill and holder for lathe #dd ,flat turret lathe1 ,acme1 examples of chuck work #bai ,hartness1 example of turning #bac ,jones ,lamson double-spindle type #bba ,floating reamer holders #bga ,flywheel1 finishing in one setting in turret lathe #ahf finishing in two settings in turret lathe #ahi machining in turret lathe #ahd turning in ,potter ,johnston automatic #bcf turning in vertical boring mill #bee ,follow-rest for lathe #bg ,forced fits1 allowances for given pressure #acc average allowance for #acj pressure generally used in assembling #acb ,fractional threads1 change gears for cutting #aga ,gage1 disk1 for angles and tapers #ig disk1 rules for setting #ih1 #ii for testing ,v-thread tool #ach standard plug1 for holes #db thread1 ,acme standard #aeg ,geometric collapsing tap #bjb ,geometric self-opening die-head #bjj ,gisholt convex attachment for vertical mill #bei ,gisholt vertical boring mill1 general description #bdb ,grinder for truing lathe centers #cd ,grinding lathe tools #fb ,hartness flat turret lathe1 example of turning #bac ,hendey relieving attachment #abc application of1 for relieving taps1 cutters and hobs #abe ,hold-back or bridle for lathe #bf1 #bg ,hollow mills for turret lathe #aih ,horizontal boring machine #bge ,detrick ,harvey floor type #bid examples of work #bhi-big ,independent chuck for lathe #cf ,index plate1 change gear1 for lathe #acg ,indicator1 center1 use on lathe #ajj for catching threads when screw cutting #ada test1 truing buttons with #ajb1 #ajc thread1 for lathe apron1 principle of #adb ,inserted cutter turning tools for lathe #eh ,internal threading #aed ,jones ,lamson double-spindle flat turret lathe #bba ,knurling in lathe and tool used #abb ,lard oil as a cutting lubricant #gh ,lathe1 boring holes to given center distance in #ea boring large castings in #di boring small hole with #ajd1 #aje cutting threads in #ace drilling small hole with #ajd general description of ,bradford #a ,le,blond crankshaft1 operation of #aaj ,lo-swing1 general description #aae method of handling when cutting threads #ach quick change-gear type #agc ,r4 ,k4 ,le,blond special crankshaft #ajh turret type1 general description #agh ,lathe centers1 grinder for truing #cd ,lathe chucks1 application of #cg universal1 independent and combination #cf ,lathe faceplate1 holding work on #de ,lathe follow-rest #bg ,lathe steadyrest #bc application of1 when boring #be ,lathe taper attachment #hh practical application of #ij ,lathe tool grinding #fb ,lathe tools1 angle of clearance #ff angle of keenness #fg application of various types #ef slope of cutting edge #ff1 #fg ,lathe turning tools1 inserted-cutter type #eh set of tools for general work #ed ,lead of thread1 definition of #adf ,le,blond1 ,r4 ,k41 lathe for crankshaft turning #ajh ,left-hand thread1 method of cutting #adh ,lining1 fixture for holding when boring #bic ,lo-swing lathe1 general description #aae example of multiple-turning #aag ,lubricant1 effect on cutting speed #gf for cooling turning tools #gg for machining aluminum #ec lard oil as a cutting #gh ,lucas horizontal boring machine #bge ,mandrel or arbor press #bb ,mandrels or arbors for lathe work1 types of #ai for lathe work1 use of #ag ,metric pitches1 change gears for cutting #aga ,micrometer for measuring threads #afb ,mills1 hollow1 for turret lathe #aih ,multiple-spindle chucking machine1 ,new ,britain #bch ,multiple-thread cutting1 indexing faceplate for #aec ,multiple threads #adf method of cutting #aej setting tool when cutting #aeb ,multiple-turning in ,lo-swing lathe #aag ,new ,britain multiple-spindle chucking machine #bch ,newall ,engineering ,co's fit allowances #aca ,pistons1 gasoline engine1 turning in turret lathe #bjd ,piston rings1 attachment for turning in turret lathe #baj turning in turret lathe #bjf ,piston turning in ,pratt ,whitney turret lathe #bjh ,pitch1 metric1 change gears for cutting #aga ,pitch of thread1 definition of #adf ,plug gage1 standard #db ,polishing and filing in lathe #ac ,potter ,johnston automatic chucking and turning machine #bbc method of setting-up #bbg turning flywheel in #bcf ,pratt ,whitney turret lathe1 arranged for piston turning #bjh equipped with piston ring turning attachment #baj ,press for arbors or mandrels #bb ,pressure generally used in assembling forced fits #acb ,push fits1 allowances for #aca ,quick change-gear type of lathe #agc ,reamer holders1 floating type #bga ,reaming and drilling in lathe #dc ,releasing die and tap holders #aii ,relieving attachment1 ,hendey #abc ,relieving attachment1 ,hendey1 application of #abe ,relieving hobs or taps having spiral flutes #abh ,rivett-,dock threading tool #afd ,roughing and finishing cuts in lathe #ge1 #gf ,running fits1 allowances for #aca ,screw cutting1 calculating change gears for #afg compound gearing for #agj in engine lathe #ace method of handling lathe #ach selecting change gears for #ace with compound rest #adc ,screws1 cutting to compensate for shrinkage #afe metric1 change gears for cutting #aga testing size of #afa ,selecting type of turning machine #bdj ,shrinkage1 cutting screws to compensate for #afe ,shrinkage fits1 allowances for #acc ,side-tool1 facing with #g ,speeds for turning1 average #gb based on ,taylor's experiments #ga effect of lubricant #gf factors which limit #gb rules for calculating #gd ,spherical turning #aaa attachments for #aac ,spider for supporting bushing while turning #dh1 #di ,spiral flutes1 method of relieving hobs or taps with #abh ,square thread and method of cutting #adi1 #aei ,steadyrest1 application of when boring #be for engine lathe #bc ,stop for lathe cross-slide when threading #aee ,tap and die holders1 releasing type #aii ,taper attachment for lathe #hh practical application of #ij ,taper boring with taper attachment #ij ,taper threading1 position of tool for #aed ,taper turning1 adjustment of tailstock center for #hb by offset-center method #hj examples of #hc height of tool for #id in vertical boring mill #bfa in vertical mill with horizontal and vertical feeds #bfb setting tailstock center with caliper tool #he setting tailstock center with square #hg with compound rest #ie with taper attachment #ib1 #ic ,tapers1 gage for accurate measurement of #ig ,tapers1 rules for figuring #ig ,test indicator1 truing buttons with #ajb1 #ajc ,test or center indicator for use on lathe #ajj ,thread cutting1 calculating change gears for #afg compound gearing for #agj cross-slide stop used for #aee indexing faceplate for multiple threads #aec in engine lathe #ace internal #aed method of handling lathe #ach selecting change gears for #ace taper1 position of tool for #aed with compound rest #adc ,thread gage1 ,acme standard #aeg ,thread indicator for lathe apron #ada1 #adb ,thread micrometer #afb ,thread tool1 ,acme1 measuring width with vernier caliper #aeg1 #aeh for cutting ,v-thread #ach ,thread tools for standard threads #aei ,threads1 ,acme standard1 and tool for cutting #aei change gears for fractional #aga cutting to compensate for shrinkage #afe different forms of #add left-hand1 method of cutting #adh metric1 change gears for cutting #aga multiple #adf multiple1 method of cutting #aej multiple1 setting tool when cutting #aeb sharp ,v1 and tool for cutting #aei square1 and method of cutting #adi1 #aei testing size of #afa three-wire system for measuring #afc ,u4 ,s4 standard1 and tool for cutting #adf1 #aei ,whitworth standard1 and tool for cutting #aeh1 #aei worm1 and tool for cutting #aei1 #afj ,threading attachment1 lathe1 for coarse threads #afj ,threading tool1 ,rivett-,dock #afd ,tool grinding #fb ,tools for lathe1 set for general turning #ed ,tools for turning1 angle of clearance #ff angle of keenness #fg inserted-cutter type #eh slope of cutting edge #ff1 #fg ,tools for turret lathe #aij ,tools1 lathe1 application of various types #ef ,turning1 cylindrical1 simple example of #f eccentric #ajf multiple1 in ,lo-swing lathe #aag with front and rear tools #aad ,turning speeds1 average for lathe #gb based on ,taylor's experiments #ga factors which limit #gb rules for calculating #gd ,turning tools1 angle of clearance #ff angle of keenness #fg for aluminum #ec for brass #eb for copper #eb for lathe1 position of #fj for lathe1 set of1 for general work #ed inserted-cutter type for lathe #eh slope of cutting edge #ff1 #fg ,turret lathe1 ,bardons ,oliver1 general description #agh examples of chuck work in ,acme flat #bai ,hartness flat1 example of turning #bac ,jones ,lamson double-spindle type #bba machining flywheels in #ahd ,pratt ,whitney arranged for piston turning #bjh piston ring turning attachment for #baj tools for general work #aij turning bevel gear blanks in ,davis #bab turning gasoline engine pistons in #bjd turning piston rings in #bjf turning worm-gear blanks in ,davis #baa typical example of turret lathe work #aha ,turret lathe tools1 miscellaneous types #bjb ,turret lathe type of vertical boring mill #bfd ,type of turning machine1 factors which govern selection #bdj ,u4 ,s4 standard thread #aei method of cutting #adf ,universal chuck for lathe #cf ,v-thread and tool for cutting #aei ,vertical boring mill1 ,bullard turret lathe type #bfd convex turning attachment #bei general description #bdb holding and setting work #bdg taper turning in #bfa taper turning with horizontal and vertical feeds #bfb tools for boring and reaming #bea turning flywheel in #bee turning tools for #bec ,vertical turret lathe1 ,bullard1 examples of work #bfh ,whitworth standard thread and tool for cutting #aeh1 #aei ,wire system for measuring threads #afc ,worm thread and tool for cutting #aei1 #afj ,transcriber's notes on changes made to text3 ,left as in original3 use of degree1 deg4 and deg42 use of minute1 min4 and '4 ,standardised to the most commonly used in the book3 backgear to back-gear2 camshaft to cam-shaft2 crankpin to crank-pin2 face-plate to faceplate2 out-board to outboard2 over-hang to overhang2 setscrew to set-screw2 steady-rest to steadyrest2 subdivision7s7 to sub-division7s72 tail-stock to tailstock2 thumbscrew to thumb-screw2 tool-post to toolpost2 tool-slide to toolslide2 hand-wheel to handwheel2 ,u4,s4 to ,u4 ,s4 ,page #fd had a blotched 7illegible7 word1 this has been replaced by 7large and rigid7 work4 ,table of ,contents3 largely re-compiled to create one-to-one links with named paragraphs and sections in text4