1 i I 1 



1 111 working vri \ of figure 3, showing the tool and signature. 



(Smithsonian photo |t>",-'y\. 1 



made for doing this so easil) that there is ever) reason 

 to believe that, originally, there wen- various differ- 

 ent spindle and nut units which could be interch 

 aliK used in the machine. Additional evidence 

 tending to support this concept exists in the cutting 

 tool (fig. 1), which must have been intended for 

 serious work as it has been carefully fitted in its 

 uns\ m metrical socket. The cutting blade of this tool, 

 which works with a scraping rathei than a true 

 Cutting action, is too wide to form a properly pro- 

 poi tinned thread when used with the existing lead 

 screw. This may well indicate that the tool was made 

 for use with a lead oi coarsei pitch, now lost. 



Perhaps the most startling feature oi this machine 

 when compared with the machine of the // 

 is the absence oi a cross-slide for adjusting the tool. 

 Possibly this can he explained by the blunt scraping 

 edge on the tool. In actual use. recently, to cut a 

 sample sc iew. using a tool similar to the one found in 

 the machine (fig. 7), it was found advantageous to be 



free of a cross-slide and thus lie able to feed the tool 

 into the work by feel rather than by rule, as would 

 be done with a slide rest. In this way, it was possible 

 to thread steel without tearing, as the cutting pr 

 could readily be felt and the tool could release 

 itself from too heavy a cut. Size on several screws 

 could be repeated b) setting the tool to produce the 

 desired diameter when its supporting arm came to 

 test against the frame of the machine. The screws 

 used in the machine itself were apparently made in 

 just such a way. They were not cut with a die as the 

 thread blends \er\ gradually into the body of the 

 screw without the characteristic marks left l>\ the 

 cutting edges of a die. Threads cut with a single- 

 point tool controlled by a cross-slide usually end 

 even more abruptU than those cut In a die. while it 

 would 1»- quite simple with a machine of the nature 

 we are considering to bring the thread to a gentle 

 tapering end as seen in figure ■'! . mother view of the 

 screw \ in fig. 3) l>\ gradually releasing the pri 



PAPER 37: SCRIW-IHKI \I> 1 1 MIM, l\\ nil MASTER-SCREW Ml fHOD 



[09 



