One importanl advance shown here is driving the 

 machine b) humus of a cord or band so that any 

 means of rotar) power could be applied, not just 

 hand 01 loot power. ( )| greater interest and tech- 

 nical importance to this stud) is the provision, seen 

 in bettei advantage in figure 11. foi readil) changing 

 from one master lead screw to another. ["hi 



i. been achieved in the Manuel Wetschgi ma- 

 chine, as fai as versatility is concerned, although not 



in quite such a convenient was . 



Figure 12, the headstock of another and more 

 advanced lathe than shown in figures 9 and 11 but 

 of the same t\ pe, shows "keys" (d), each ol which is a 

 p irti il nui of different pitch to engage with a thread 

 ol mating pitch. The dotted lines in figure 13 show 

 the engaged and disengaged positions of one ol these 

 ke\s, .nui I'm i ii e 11 shows the spindle with the variou 

 leads, c. At D is a grooved collar to he engaged h\ 



the narrow key shown in operating position at the 



left in figure 12 lor the purpose of controlling the 

 endwise movement of the spindle when used for 

 ordinary turning instead ol' thread-cutting. In return 

 lor greater convenience and freedom from the expense 

 of the many separate spindles, as typified by the 

 Wetschgi machine, a sacrifice has been made in the 

 length of the thread which can he cm withoul 

 interruption, 



1 Ins reduction in the length thai could conveniently 



lie threaded was no '.Meat draw hack on main elasses 



'igure 7 Inn u 01 M' 'in RN I ' >u\\ I i 

 cut. using the old screw anil mil hul with a 



m-w tool. I he material threaded i~ carl - 



steel drill rod Smithsonian photo m. 1 r6 \ 



Figure 8. Binding si rj w seen at \ in figure 3, showing the long smooth fadeout of the thread 

 below the shoulder. (Smithsonian photo (9276.) 



PAPER 37: SCREW-THREAD it [TING BY THE MASTKR-SCRKW Ml 



Ill 



