,transcriber's ,notes3  ,this is ,paper 
#cg from the ,smithsonian ,institution  
,united ,states ,national ,museum       
,bulletin #bdj1 comprising ,papers      
#cd-dd1 which will also be available as 
a complete e-book4  ,the front material1
 introduction and relevant index entries
 from the ,bulletin are included in each
 single-paper e-book4  ,typographical   
errors have been corrected as follows3  
,page #aaj3 444 the spindle1 to prevent 
444 7had pindle7   ,page #abj3 444      
servants  l'intelligence de plusieurs   
choses difficiles1                      
ncessaires 444 7had a1 plusiers1        
necessaires7     ,,smithsonian          
,,institution  ,,united ,,states        
,,national ,,museum  ,,bulletin #bdj    
,illustration  ,,smithsonian ,,press    
,,museum ,,of ,,history ,,and           
,,technology    ,,contributions   ,,from
 ,,the   ,,museum   ,,of ,,history ,,and
   ,,technology    ,papers #cd-dd   ,on 
,science and ,technology  ,,smithsonian 
,,institution  ,,washington1 ,d4,c4     

#aiff     ,publications of the ,united  
,states ,national ,museum   ,the        
scholarly and scientific publications of
 the ,united ,states ,national ,museum  
include two series1 ,proceedings of the 
,united ,states ,national ,museum and   
,united ,states ,national ,museum       
,bulletin4  ,in these series1 the       
,museum publishes original articles and 
monographs dealing with the collections 
and work of its constituent             
museums--,the ,museum of ,natural       
,history and the ,museum of ,history and
 ,technology--setting forth newly       
acquired facts in the fields of         
anthropology1 biology1 history1 geology1
 and technology4 ,copies of each        
publication are distributed to          
libraries1 to cultural and scientific   
organizations1 and to specialists and   
others interested in the different      
subjects4  ,the ,proceedings1 begun in  
#ahgh1 are intended for the publication1
 in separate form1 of shorter papers    
from the ,museum of ,natural ,history4  

,these are gathered in volumes1 octavo  
in size1 with the publication date of   
each paper recorded in the table of     
contents of the volume4  ,in the        
,bulletin series1 the first of which was
 issued in #ahge1 appear longer1        
separate publications consisting of     
monographs 7occasionally in several     
parts7 and volumes in which are         
collected works on related subjects4    
,bulletins are either octavo or quarto  
in size1 depending on the needs of the  
presentation4 ,since #aijb papers       
relating to the botanical collections of
 the ,museum of ,natural ,history have  
been published in the ,bulletin series  
under the heading ,contributions from   
the ,united ,states ,national           
,herbarium1 and since #aiei1 in         
,bulletins titled ,contributions from   
the ,museum of ,history and ,technology1
 have been gathered shorter papers      
relating to the collections and research
 of that ,museum4  ,the present         
collection of ,contributions1 ,papers   

#cd-dd1 comprises ,bulletin #bdj4 ,each 
of these papers has been previously     
published in separate form4 ,the year of
 publication is shown on the last page  
of each paper4    ,,frank ,a4 ,,taylor  
,director1 ,united ,states ,national    
,museum     ,,contributions ,,from ,,the
 ,,museum ,,of ,,history ,,and          
,,technology3 ,,paper #cg               
,,screw-,,thread ,,cutting ,,by ,,the   
,,master-,,screw ,,method ,,since #adhj 
,edwin ,a4 ,battison     ,edwin ,a4     
,battison  ,,screw-,,thread ,,cutting   
,,by ,,the ,,master-,,screw ,,method    
,,since #adhj      ,among the earliest  
known examples of screw-thread cutting  
machines     are the screw-cutting lathe
 of #adhc1 known only in pictures and   
drawings1 and an instrument of the      
traverse-spindle variety for            
threading metal1 now in the ,smithsonian
 ,institution1 dating from the     late 
#agth or early #ahth century4 ,the      
author shows clearly their     evolution
 from something quite specialized to the

 present-day tool4     ,he has traced   
the patents for these instruments       
through the early     #aicj's and from  
this research we see the part played by 
such devices     in the development of  
the machine-tool industry4      ,,the   
,,author3 ,edwin ,a4 ,battison is       
associate curator of mechanical     and 
civil engineering in the ,smithsonian   
,institution's ,museum of     ,history  
and ,technology4   ,directness and      
simplicity characterize pioneer machine 
tools because they were intended to     
accomplish some quite specialized task  
and the need for versatility was not    
apparent4 ,history does not reveal the  
earliest forms of any primitive machines
 nor does it reveal much about the      
various early stages in evolution toward
 more complex types4 ,at best we have   
discovered and dated certain            
developments as existing in particular  
areas4 ,whether these forms were new at 
the time they were first found or how   
widely dispersed such forms may have    

been is unknown4 ,surviving evidence is 
in the form of pictures or drawings1    
such as the little-known screw-cutting  
lathe of #adhc 7fig4 #a7 shown in ,das  
mittelalterliche ,hausbuch4  ,this lathe
 shows that its builder had a keen      
perception of the necessary elements1   
reduced to bare essentials1 required to 
accomplish the object4 ,present are the 
coordinate slides often credited to     
,henry ,maudslay4 ,his slides are not1  
of course1 associated with the spindle2 
neither is there any natural law which  
compels them to guide the tool exactly  
parallel with the axis of revolution4   
,in this sense the screw-cutting lathe  
in the ,hausbuch is superior because it 
is in harmony with natural law and can  
generate a true cylinder1 whereas       
,maudslay's lathe can only transfer to  
the work whatever accuracy is built into
 it4  ,in principle this machine shown  
in the ,hausbuch is very advanced as we 
see when we follow the design through to
 the present time4 ,the artist1 whose   

drawings give us our only knowledge of  
the machine1 himself was obviously not  
very familiar with the details of its   
function4 ,reference to figure #a shows 
that the threads on the lead screw and  
on the work1 wind in opposite           
directions4 ,this must be an error in   
delineation since the two are closely   
coupled together without any intervening
 mechanism so that the only possible    
result on the work must be a thread     
winding in the same direction as on the 
original screw4 ,the work also is shown 
threaded for its entire length2 this    
cannot be accomplished with any one     
location of the cross-slide4 ,we are    
left with the question of whether this  
slide was used in two locations or      
whether the artist1 possibly working    
from notes or an earlier rough sketch1  
failed to show an unthreaded portion on 
one end or the other of the work4       
,illustration3 ,figure #a4--;,,earliest 
,,representation ,,found ,,of ,a        
,,master-,,screw ,,type of              

thread-cutting machine4 ,from the       
inconsistencies1 such as right- and     
left-hand threads on master and work1 it
 appears that the artist had scant      
insight into actual function4 ,from     
plate #fb of ,das mittelalterliche      
,hausbuch1 nach dem ,originale im       
,besitze des ,frsten von                
,waldburg-,wolfegg-,waldsee1 im         
,auftrage des ,deutschen ,vereins fr    
,kunstwissenschaft1 herausgegeben von   
,helmuth ,th4 ,bossert und ,willy ,f4   
,storck 7,leipzig3 ,e4 ,a4 ,seemann1    
#aiab74  ,of at least equal importance  
with the lead screw and work and their  
relationship to each other is the       
tool-support with its screw-adjusted    
cross-slide 7fig4 #b74 ,just how this   
was attached to the frame of the machine
 so that it placed the tool at a        
suitable radius is again a questionable 
point4 ,the very well-developed cutting 
tool is sharpened to a thin1 keen edge  
totally unsuited for cutting metal but  
ideal for use on a softer1 fibrous      

substance3 undoubtedly wood1 in this    
instance4 ,unfortunately1 the angle at  
which the artist chose to show us this  
cutter is not a view from which it is   
possible to judge whether or not the    
tool has been made to conform to the    
helix angle of the thread to be cut4    
,this cross-slide1 in conjunction with  
the traversing work spindle1 gives us a 
machine having two coordinate slides    
yielding the same effect as the slide   
rest usually attributed to ,henry       
,maudslay at the end of the #ahth       
century4 ,actually1 an illustration of  
coordinate slides independent of the    
spindle had been published as early as  
#aefi by ,besson#a and knowledge of them
 widely disseminated by his popular work
 on mechanics4 ,these slides are shown  
as part of a screw-cutting machine with 
a questionably adequate connection1 by  
means of cords1 between the master screw
 and the work4  ,it was the author's    
pleasure recently to obtain for the     
,smithsonian ,institution and identify a

 small1 nicely made1 brass instrument   
which had been in two collections in    
this country and one collection in      
,germany as an unidentified locksmith's 
tool 7fig4 #c74 ,this proved to be an   
instrument of the traverse-spindle      
variety for threading metal4            
,fortunately1 all essential details were
 present including a cutter 7,a in      
figure #d72 this instrument was         
identified by the signature ,manuel     
,wetschgi1 ,augspurg4 ,the ,wetschgis   
were a well-known family of gunsmiths   
and mechanics in ,augsburg through      
several generations4 ,two bore the given
 name ,emanuel3 the earlier was born in 
#afgh and died in #agbh4 ,he was quite  
celebrated in his field of rifle making 
and became chief of artillery to the    
,landgrave of ,hesse-,kassel shortly    
before his death in his #east year4     
,little is known of the later ,emanuel  
,wetschgi except that he was at         
,augsburg in #agdj4 ,tentative          
attribution of the instrument has been  

made to the earlier ,emanuel1 chiefly on
 the basis of his recognized position as
 an outstanding craftsman4              
,illustration3 ,figure                  
#b4--;,,cross-,,slide for the           
thread-cutting lathe of ,das            
mittelalterliche ,hausbuch1 shown in    
figure #a4 ,it is remarkable not only   
for its early date1 but also for its    
high state of development with a        
crossfeed screw which had not become    
universally accepted #cjj years later4  
,the cutter1 shown out of its socket1 is
 obviously sharpened for use on wood4   
,in several respects this little machine
 differs from its predecessor of the    
,hausbuch1 as might be expected when    
allowance is made for the generations of
 craftsmen who undoubtedly worked with  
such tools over the roughly #bjj years  
of time separating them4 ,another factor
 to consider when comparing these two   
machines is that one was used on metal1 
the other probably only on wood4        
,therefore1 it is not surprising to find

 on the later machine an outboard or    
tailstock support for the work4 ,the    
spindle of this support has to travel in
 unison with the work-driving spindle so
 that it is not an unexpected discovery 
to find that it is spring-loaded4       
,figure #e shows how this spring may be 
adjusted to accommodate various lengths 
of work by moving the attachment screw  
to various holes in both the spring and 
in the frame4 ,also visible in the same 
illustration is a rectangular projection
 at the other end of the spring which   
engages a mating hole in the tailstock  
spindle to prevent its rotation4        
,illustration3 ,figure #c4--,,small     
,,thread-,,cutting ,,lathe which was    
made to be held in a vise during use4   
,it was found as shown here1 with only  
the operating crank missing4 ,the       
overall length is approximately #ab     
inches1 depending on the adjustment of  
parts4 7,smithsonian photo #dfebe;,b47  
,figure #f shows the traversing spindle 
and nut removed from the machine4       

,provision has been made for doing this 
so easily that there is every reason to 
believe that1 originally1 there were    
various different spindle and nut units 
which could be interchangeably used in  
the machine4 ,additional evidence       
tending to support this concept exists  
in the cutting tool 7fig4 #d71 which    
must have been intended for serious work
 as it has been carefully fitted in its 
unsymmetrical socket4 ,the cutting blade
 of this tool1 which works with a       
scraping rather than a true cutting     
action1 is too wide to form a properly  
proportioned thread when used with the  
existing lead screw4 ,this may well     
indicate that the tool was made for use 
with a lead of coarser pitch1 now lost4 
,illustration3 ,figure #d4--,,the       
,,working ,,area of figure #c1 showing  
the tool and signature4 7,smithsonian   
photo #dfebe;,a47  ,perhaps the most    
startling feature of this machine when  
compared with the machine of the        
,hausbuch1 is the absence of a          

cross-slide for adjusting the tool4     
,possibly this can be explained by the  
blunt scraping edge on the tool4 ,in    
actual use1 recently1 to cut a sample   
screw1 using a tool similar to the one  
found in the machine 7fig4 #g71 it was  
found advantageous to be free of a      
cross-slide and thus be able to feed the
 tool into the work by feel rather than 
by rule1 as would be done with a slide  
rest4 ,in this way1 it was possible to  
thread steel without tearing1 as the    
cutting pressure could readily be felt  
and the tool could release itself from  
too heavy a cut4 ,size on several screws
 could be repeated by setting the tool  
to produce the desired diameter when its
 supporting arm came to rest against the
 frame of the machine4 ,the screws used 
in the machine itself were apparently   
made in just such a way4 ,they were not 
cut with a die as the thread blends very
 gradually into the body of the screw   
without the characteristic marks left by
 the cutting edges of a die4 ,threads   

cut with a single-point tool controlled 
by a cross-slide usually end even more  
abruptly than those cut by a die1 while 
it would be quite simple with a machine 
of the nature we are considering to     
bring the thread to a gentle tapering   
end as seen in figure #h 7another view  
of the screw ,a in fig4 #c7 by gradually
 releasing the pressure necessary to    
keep the tool cutting as the end of the 
thread was approached4  ,illustration3  
,figure #e4--,,spring ,,for ,,keeping   
,,the ,,follower ,,spindle against the  
work1 showing the method and range of   
adjustment4 ,note the rectangular       
projection to engage a mating socket in 
the spindle1 to prevent spindle         
rotation4 7,smithsonian photo #dfebe47  
,illustration3 ,figure #f4--,,work      
,,spindle ,,and ,,its ,,nut removed from
 the machine to illustrate how easily   
another spindle and nut of different    
pitch could be substituted4             
7,smithsonian photo #dfebe;,c47  ,that  
machines of this general type having the

 lead screw on the axis of the work were
 competitive with other methods and     
other types of machines over a long     
period of time may be seen from figures 
#i and #aj4 ,the machine1 left front in 
figure #i and in more intimate detail in
 figure #aj1 can be seen to differ      
little from that shown in ,das          
mittelalterliche ,hausbuch of #adhc4    
,the double work-support is1 of course1 
a great improvement1 while the          
tool-support is regressive since it     
lacks a feed screw4  ,the development of
 engineering theory1 coupled with the   
rising needs of industry1 particularly  
with the advent of the ,industrial      
,revolution1 brought about accelerated  
development of screw-cutting lathes     
through the combination of screw-cutting
 machines with simple lathes as seen in 
figure #i and in detail in figure #aa4  
,one important advance shown here is    
driving the machine by means of a cord  
or band so that any means of rotary     
power could be applied1 not just hand or

 foot power4 ,of greater interest and   
technical importance to this study is   
the provision1 seen to better advantage 
in figure #aa1 for readily changing from
 one master lead screw to another4 ,this
 had already been achieved in the       
,manuel ,wetschgi machine1 as far as    
versatility is concerned1 although not  
in quite such a convenient way4         
,illustration3 ,figure #g4--,,thread    
,,of ,,modern ,,form recently cut1 using
 the old screw and nut but with a new   
tool4 ,the material threaded is         
carbon-steel drill rod4 7,smithsonian   
photo #dibgf;,a47  ,figure #ab1 the     
headstock of another and more advanced  
lathe than shown in figures #i and #aa  
but of the same type1 shows keys 7,d71  
each of which is a partial nut of       
different pitch to engage with a thread 
of mating pitch4 ,the dotted lines in   
figure #ac show the engaged and         
disengaged positions of one of these    
keys1 and figure #ad shows the spindle  
with the various leads1 ,c4 ,at ,d is a 

grooved collar to be engaged by the     
narrow key shown in operating position  
at the left in figure #ab for the       
purpose of controlling the endwise      
movement of the spindle when used for   
ordinary turning instead of             
thread-cutting4 ,in return for greater  
convenience and freedom from the expense
 of the many separate spindles1 as      
typified by the ,wetschgi machine1 a    
sacrifice has been made in the length of
 the thread which can be cut without    
interruption4  ,illustration3 ,figure   
#h4--;,,binding ,,screw seen at ,a in   
figure #c1 showing the long smooth      
fadeout of the thread below the         
shoulder4 7,smithsonian photo #dibgf47  
,illustration3 ,figure #i4--,,making    
,,screws ,,in ,,france in the third     
quarter of the #ahth century4 ,from     
,l',encyclopdie1 ou dictionnaire raisonn
 des sciences1 des arts et des mtiers   
444 receuil de planches sur les         
sciences1 les arts libraux1 et les arts 
mchaniques1 avec leur explication       

7,paris3 #agfb-aggb71 vol4 #i1 plate #a4
  ,illustration3 ,figure                
#aj4--;,,details ,,of ,,the ,,machine in
 the left foreground of figure #i1      
showing the crude tool-support without  
screw adjustment4 ,from ,l',encyclopdie1
 vol4 #i1 plate #b4  ,this reduction in 
the length that could conveniently be   
threaded was no great drawback on many  
classes of work4 ,this can be realized  
from figure #af which shows a           
traverse-spindle lathe headstock typical
 of the mid-#aith century4 ,during the  
years intervening between the machines  
of figures #ab and #af1 the general     
design was greatly improved by removing 
the lead screws from the center of the  
spindle4 ,this made possible a shorter1 
much stiffer spindle and supported both 
ends of the spindle in one frame or     
headstock rather than in separate pieces
 attached to the bed4 ,the screws were  
now mounted outside of the              
spindle-bearings1 one at a time1 while  
the mating nuts were cut partially into 

the circumference of a disk which could 
be turned to bring any particular nut   
into working position as required4 ,with
 this arrangement1 a wide variety of    
leads either right or left hand could be
 provided and additional leads could be 
fitted at any future time4              
,screw-cutting lathes of this design    
were popular for a very long time with  
instrument makers and opticians who had 
little need to cut screws of great      
length4  ,illustration3 ,figure         
#aa4--;,,details ,,of ,,the ,,threading 
,,lathe seen in the right foreground of 
figure #i showing the method of drive   
and support for the work4 ,from         
,l',encyclopdie1 vol4 #i1 plate #a4     
,the demands of expanding industry for  
greater versatility in the production of
 engineering elements late in the #ahth 
century set the stage for the evolution 
of more complex machines tending to     
place the threaded spindle lathes in    
eclipse4 ,maudslay's lathe of #agig-ahjj
 7fig4 #ae7 appeared at this time when  

industry was receptive to rapid         
innovation4 ,unfortunately1 the gearing 
which once existed to connect the       
headstock spindle with the lead screw   
has long been lost4 ,at this time it is 
quite difficult to say with certainty   
whether the original gear set offered a 
variety of ratios1 as was true of       
slightly later ,maudslay lathes1 or a   
fixed ratio4 ,the plausibility of the   
fixed ratio theory is supported by the  
very convenient means1 seen in figure   
#ae1 for removing the lead screw in     
preparation for substitution of one of  
another pitch4 ,all that is required is 
to back off its supporting center at the
 tailstock end and withdraw the screw   
from its split nut#b and from the       
driving clutch near the headstock4 ,this
 split nut also would have to be changed
 to one of a pitch corresponding to that
 of the screw4 ,while more expensive    
than a solid nut1 it neatly circumvents 
the need 7and saves the time involved7  
to reverse the screw in order to get the

 tool back to the point of beginning    
preliminary to taking another cut4      
,david ,wilkinson's lathe of #agih 7fig4
 #ag7 which was developed in ,rhode     
,island at the same time shows the same 
method of mounting and driving the      
master screw4 ,at least in the ,united  
,states1 this method of changing the    
lead screw instead of using change gears
 remained popular for many years4       
,examples of this changeable screw      
feature are to be found in the lathes   
constructed for the pump factory of ,w4 
,b4 ,douglas ,company1 ,middletown1     
,connecticut1#c in the #ahcj's4         
,middletown1 at that time one of the    
leading metal-working centers in one of 
the chief industrial ,states1 had been  
for many years the site of the ,simeon  
,north arms factory which rivaled       
,whitney's4 ,in this atmosphere1 it is  
reasonable to expect that machinery     
constructed by local mechanics1 as was  
the custom in those days1 would reflect 
the most accepted refinements in machine

 design4  ,illustration3 ,figure        
#ab4--,,well-,,developed ,,example of   
lathe headstock having several leads on 
the spindle and provision for mounting  
the work or a work-holding chuck on the 
spindle4 ,adapted from ,l',encyclopdie1 
vol4 #aj1 plate #ac4  ,illustration3    
,figure #ac4--;,,end ,,view ,,of ,,the  
,,headstock seen in figure #ab1 showing 
the keys or half nuts which engage the  
threaded spindle1 in engaged and        
disengaged positions4 ,from             
,l',encyclopdie1 vol4 #aj1 plate #ac4   
,illustration3 ,figure #ad4--,,spindle  
,,of ,,figures #ab ,,and #ac1 showing   
the several leads and the many-sided    
seat for the driving pulley4 ,note the  
scale of feet4 ,from ,l',encyclopdie1   
vol4 #aj1 plate #af4  ,roughly twenty   
years later1 ,joseph ,nason of ,new     
,york patented#d the commercially very  
important ,fox brassworker's lathe 7fig4
 #ah74 ,while this does have a ratio in 
the pair of gears connecting the work   
spindle and master screw1 it is clear   

from the patent that various pitches are
 to be obtained by changing screws1 not 
by changing gears4 ,the patent sums it  
up as follows3       ,a nut upon the end
 of the stud 444 is unscrewed when the  
guide      screw is to be removed or    
changed4 ,the two wheels 444 should have
      in their number of teeth a common 
multiple4 ,they are seldom or      never
 removed and their diameters are made   
dissimilar only for the      purpose of 
giving to the guide screw a slower rate 
of motion than      that of the mandrel 
whereby it may be made of coarser pitch 
than      that of the screw to be cut   
and its wear materially lessened4  ,the 
introduction of gearing between the     
spindle and the lead screw1 for whatever
 purpose1 could not help but introduce  
variable factors caused by inaccuracies 
in the gears themselves and in their    
mounting4 ,these were of little         
consequence for common work1            
particularly when coupled to a screw    
which1 itself1 was of questionable      

accuracy4 ,the increasing refinements   
demanded in scientific instruments and  
in machine tools themselves after they  
had reached a relatively stable form    
dictated that attention be dedicated to 
improved accuracy of the threaded       
components4  ,illustration3 ,figure     
#ae4--,,maudslay',s ,,well-,,known      
screw-cutting lathe of #agig-ahjj1      
showing the method of mounting and      
driving changeable master screws4       
7,photo courtesy of ,the ,science       
,museum1 ,london47  ,illustration3      
,figure #af4--;,,headstock ,,of ,a      
,,german ,,instrument-,,maker',s        
,,lathe1 typical of the mid-#aith       
century1 showing the traverse spindle1  
interchangeable lead screws1 and        
semicircumferential nut containing      
several leads4 ,the nut may be brought  
into engagement by the lever at top rear
 of the headstock4 ,this releases the   
end thrust control on the spindle       
simultaneously with engagement of the   
nut4 7,smithsonian photo #dihci47       

,illustration3 ,figure #ag4--;,,david   
,,wilkinson',s ,,screw-,,cutting        
,,lathe1 patented in the ,united ,states
 in #agih4 ,note the ready facility with
 which the lead screw may be exchanged  
for another and the same means of       
supporting and driving as in figure #ae4
 7,u4,s4 ,national ,archives photo47    
,an attack on this problem1 which       
interestingly reverts to the fundamental
 principle of motion derived from a     
master screw without the intervention of
 other mechanism 7fig4 #ai71 is covered 
by a patent#e issued to ,charles ,vander
 ,woerd1 one-time superintendent of the 
,waltham ,watch ,company4 ,the problem  
is well stated in the patent3           
,this invention relates to the          
manufacture of leading screws to be     
used for purposes requiring the highest 
attainable degree of      correctness in
 the cutting of the screw-threads of    
said screw 444      as1 for example1 in 
machines for ruling lines in glass      
plates to      produce refraction sic   

gratings for the resolution of the lines
      of the solar spectrum1 such       
machines being required to rule many    
thousands of lines on an inch of space  
by a marking device which is            
reciprocated over the glass plate and is
 fed by the action of a      leading    
screw after the formation of each line4 
,great difficulty      has been         
experienced in constructing a leading   
screw for this and      other purposes1 
in which the thread is so nearly correct
 as to      produce no perceptible      
variation in the microscopic spaces     
between      the ruled lines or         
gratings4444 ,various causes prevent the
      formation of a thread on the rod  
or blank1 which is absolutely           
uniform and accurate from end to end of 
the rod4 ,among other causes      are   
the variations of temperature from time 
to time1 the      imperfections of the  
operating leading screw1 the springing  
of the      leading screw and of the rod
 that is being threaded1 and other      

unavoidable causes1 all of which1       
although apparently trivial and         
producing only slight variations in the 
thread at different parts      of the   
rod or blank1 are of sufficient moment  
to be seriously      considered when a  
screw of absolute accuracy is desired4  
,illustration3 ,figure #ah4--,,nason',s 
,,lathe1 patented in #ahed1 showing a   
master lead screw driven at less than   
work speed so that the master could be  
of a coarser and more durable pitch than
 the work4 ,u4,s4 patent #ajchc4  ,it is
 interesting to note in figure #ai that 
,vander ,woerd's machine1 to avoid the  
problems outlined in his patent1 has    
returned to a starkly simple design4 ,we
 are not told1 however1 how he          
originated this master screw which is   
used to produce the accurately threaded 
work pieces4 ,later generations1 in the 
search for ever-greater accuracy1 also  
returned to the fundamental simplicity  
of a master screw as we shall see when  
we consider the refinements in mechanism

 necessary to the extended development  
of the automobile and the airplane4     
,illustration3 ,figure #ai4--,,vander   
,,woerd',s ,,patent1 seen here1 covered 
the combination of a master screw1      
toolslide and work in a rigid frame to  
be supported and driven by outside means
 of no required precision4 ,u4,s4 patent
 #bicicj dated ,february #ahhd4  ,as the
 power and speed of automobiles and     
aircraft increased1 critical parts      
became more highly stressed4 ,gears and 
threaded parts were particularly        
troublesome details of the mechanism    
because of the stresses concentrated in 
them1 and1 in the case of gears1 because
 of the internal and external stresses  
originating in minute deviations from   
the ideal of tooth form and spacing4    
,the problems were not entirely new but 
had hitherto been solved by increasing  
the size of the parts1 an avenue of     
limited utility to designers in these   
fields where total weight as well as the
 effects of mass and inertia are so     

important4 ,by making these parts of    
heat-treated steel1 the strength could  
be made suitable while the size and mass
 of the parts were kept within bounds4  
,the necessary processes of             
heat-treating were not always applicable
 to finished parts as they sometimes    
destroyed both finish and accuracy4     
,grinding1 which was well developed for 
the simple plane1 cylindrical1 and      
conical surfaces so widely used in      
mechanisms1 had to be extended to       
threads and gears so that they could be 
finished after heat-treating4 ,sometimes
 the gear teeth themselves were ground2 
for other applications it was sufficient
 to improve the accuracy of the gear    
cutters4  ,illustration3 ,figure        
#bj4--;,a ,,hob-,,grinding ,,machine    
patented in #aicb and incorporating the 
master-screw principle4 ,carl ,g4       
,olson's ,u4,s4 patent #ahgdeib4        
,attempts to produce gear hobs free of  
the imperfections and distortions       
introduced by heat treatment led to     

another return to the use of the master 
lead screw4 ,figure #bj illustrates a   
machine having this feature which was   
patented in #aicb by ,carl ,g4 ,olson4#f
 ,in speaking of the spindle-driving    
mechanism disclosed in earlier patents1 
the patent goes on to say3       ,this  
driving mechanism includes an integral  
spindle #bj1 one      extremity thereof 
being designed for supporting a hob #bb 
and the      other extremity thereof    
being formed so as to present a lead    
screw      #bd4 ,the spindle #bj is     
mounted between a bearing #bf and a     
bearing      #bh1 the latter bearing    
providing a nut in which the lead screw 
#bd      rotates4444 ,from the          
description thus far given it will be   
apparent      that the rotation of the  
lead screw #bd within the bearing or nut
 #bh      will cause the hob to be moved
 axially1 the lead of the screw #bd     
being equal to the lead of the thread in
 the hob4  ,claim #h which concludes the
 descriptive portion of the patent      

states in part3       ,in a hob grinding
 machine of the class described1 a      
rotary work      supporting spindle1    
means for effecting longitudinal        
movement of      the spindle1 a tool    
holder for supporting a grinding wheel  
in      operative position with respect 
to the work supported by the            
spindle during the rotary and           
longitudinal movement thereof1 444      
,even before this patent was applied    
for1 another patent was pending for the 
purpose of modifying the pitch of the   
lead screw without the use of change    
gears in spite of the wide acceptance of
 such gear mechanisms for over a hundred
 years4  ,illustration3 ,figure         
#ba4--;,a ,,hob-,,grinding ,,machine    
,,of #aicc1 showing use of the master   
screw with a modifier but without change
 gears4 ,carl ,g4 ,olson's ,u4,s4 patent
 #aijaibf4  ,illustration3 ,figure      
#bb4--;,a ,,sine-,,bar ,,device to      
modify the effective lead of a master   
lead screw without introducing a complex

 mechanism which would be both difficult
 to make and to operate within the      
required close limits4 ,carl ,g4        
,olson's 7#aicc7 ,u4,s4 patent #aijaibf4
  ,figure #ba shows a plan view#g of the
 machine1 and figure #bb a detailed view
 of the sine-bar mechanism actuated by  
the master screw1 #f1 to modify the     
effective pitch of the lead screw in    
accordance with the realities of        
practice as stated in the preamble of   
the patent3       ,this invention       
relates to material working machines1   
and      particularly to machines such  
as hob grinders and the like1 wherein   
the work is reciprocated through the    
agency of a lead screw4       ,in the   
manufacture of hobs it is common        
practice to employ the same      machine
 for grinding hobs of varied diameters1 
and in order to      employ such a      
machine in this manner the pitch of the 
lead screw1      thereof1 which actuates
 the work carrier1 must conform to the  
axial      pitch of the hob to be       

ground4 ,this will be readily apparent  
when      it is understood that the     
helix angles of hobs vary in accordance 
with their diameters and1 consequently1 
the difference between the      normal  
pitch and the axial pitch               
correspondingly varies4 ,while the      
requirement for the normal pitch may be 
the same for hobs of      different     
diameters1 it is necessary to change the
 axial pitch in      accordance with a  
change in the hob diameter1 and this    
axial pitch      of the hob is equal to 
the pitch of the lead screw which       
actuates      the work carrier in       
grinding machines heretofore used4      
,hence1 in      order to adapt such     
machines to cover a wide range of leads1
 it is      necessary to provide a large
 number of interchangeable lead screws  
and obviously this represents a large   
investment1 and the      interchanging  
of these screws requires the expenditure
 of      considerable time in setting up
 the machine for each job4              

,thread-grinding machines were being    
designed concurrent with the development
 of hob-grinding machines4 ,many were   
entirely concerned with features        
peculiar to the problems of             
wheel-dressing and to automatic         
characteristics4 ,an invention to embody
 the use of a master screw and concerned
 with the precision grinding of worm    
threads1 for use in gearing1 was        
patented by ,frederick ,a4 ,ward in this
 era4#h ,that part of the invention     
pertaining to the use of a master screw1
 a rotary work holder mounted on said   
carriage and provided with a driving    
spindle1 an exchangeable master screw   
and stationary nut detachably secured to
 said spindle and head1444 is shown in  
figure #bc4  ,illustration3 ,figure     
#bc4--;,,details ,,of ,a ,,work         
,,spindle ,,with ,,work1 showing the use
 of a master lead screw to control the  
pitch of a precision worm thread being  
ground4 ,from the #aicc ,u4,s4 patent   
#ahiifed1 of ,f4 ,a4 ,ward's            

worm-grinding machine4  ,machines       
embodying the principle of the master   
lead screw are found in constant use by 
industry at the present time for        
specialized application4 ,whenever      
technological changes again reopen the  
topic of thread-cutting to a new degree 
of accuracy or call for a reevaluation  
of popular methods for any other reason1
 we may expect to see another resurgence
 of the master-screw method1 for no     
other design eliminates so many         
variables or rests on such firm and     
fundamental natural principles as the   
machine of ,das mittelalterliche        
,hausbuch of #adhc1 the earliest such   
machine now known4   ,,footnotes3  #a   
,,jacques ,,besson1 ,des instruments    
mathmatiques1 et mchaniques1 servants   
l'intelligence de plusiers choses       
difficiles1  necessaires  toutes        
rpubliques1 #ast ed4 7,orleans1 #aefi74 
,also available in later editions in    
,french1 ,german1 and ,spanish4  #b ,j4 
,,foster ,,petree1 introduction1 ,henry 

,maudslay1 #agga-ahca1 and ,maudslay    
,sons and ,field1 ,ltd4 7,london3 ,the  
,maudslay ,society1 #aidi74  #c         
,american ,machinist 7,september #bh1   
#aiaf71 vol4 #de1 no4 #ac1 pp4 #ebi-eca4
  #d ,u4,s4 patent #ajchc issued to     
,joseph ,nason of ,new ,york1 ,january  
#c1 #ahed4  #e ,u4,s4 patent #bicicj    
issued to ,charles ,vander ,woerd of    
,waltham1 ,massachusetts1 ,february #ai1
 #ahhd4  #f ,u4,s4 patent #ahgdeib1     
filed ,june #h1 #aibi1 issued to ,c4 ,g4
 ,olson of ,chicago1 ,illinois1 ,august 
#cj1 #aicb1 and assigned to the         
,illinois ,tool ,works1 also of         
,chicago4  #g ,u4,s4 patent #aijaibf1   
filed ,february #af1 #aibh1 issued to   
,c4 ,g4 ,olson of ,chicago1 ,illinois1  
,march #ba1 #aicc1 and assigned to the  
,illinois ,tool ,works1 also of         
,chicago4  #h ,u4,s4 patent #ahiifed1   
filed ,august #ca1 #aica1 issued to ,f4 
,a4 ,ward of ,detroit1 ,michigan1       
,february #bh1 #aicc1 and assigned to   
the ,gear ,grinding ,company of         

,detroit1 ,michigan4         99       99
       99       99       99  ,u4,s4     
,,government ,,printing ,,office3 #aifd 
,for sale by the ,superintendent of     
,documents1 ,u4,s4 ,government ,printing
 ,office ,washington1 ,d4,c4            
#bjdjb--,price #bj cents   ,,index      
,besson1 ,jacques1 #ajg     ,douglas1   
,w4  ,b41 ,company1 #aac     ,maudslay1 
,henry1 #ajf1 #aac     ,nason1 ,joseph1 
#aad    ,north1 ,simeon1 arms factory1  
#aad     ,olson1 ,carl ,g41 #aah        
,vander ,woerd1 ,charles1 #aaf1 #aag    
,ward1 ,frederick ,a41 #abj             
,wetschgi1 ,emanuel1 #ajh    ,wetschgi1 
,manuel1 #ajh1 #aaa    ,whitney arms    
factory1 #aad    ,wilkinson1 ,david1    
#aac