PRECISION TOOL MAKING 



381 



shows the shaving and perforating punch and die for the impulse 

 wheel, together with an illustration of the part and the stock removed 

 from the outer edge in the shaving operation which amounts to 

 about .008 in. This tool is built to have a clearance between the 

 shaving punch A and the die opening B of only two to four ten-thou- 



Fig. 6 — Cross-section of second operation shaving punch and die for 

 message register pinion. 



sandths of an inch all around, and the punch must be located very ac- 

 curately so that it will center in the die within this amount of clearance. 

 The shaving perforator C for the center hole also has practically the same 

 limit as has also the shedder D. Holes or openings in the die are held 

 to as close as .0005 in. of their nominal dimensions and also with 

 respect to each other. Fig. 6 is a partial cross-section of the second 

 operation shaving punch and die for the message register pinion, 

 which is made to similarly accurate limits. However, the close 

 workmanship on parts of this tool is also necessary in order to insure 

 interchangeability of tool parts, which will be referred to later. 



