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BELL SYSTEM TECHNICAL JOURNAL 



as shown in Fig. 20. By means of a screw press, the punch is then 

 forced into the die opening already completed, to a depth of approxi- 

 mately 1/64 in., and an accurate impression of the correct punch 

 section obtained, as shown in the figure. The punch is then milled to 

 form on the bench milling machine to within about .0005 in. to .001 in. 

 of the nominal, the outline of the impression being used as a guide in 

 this operation. The final shearing of the punch in the die, which 

 amounts to practically a shaving operation, is accomplished in several 

 steps, the excess metal being removed by filing after each operation, 

 and the punch worked down until it enters the die to the required 

 depth. The punch is then hardened, after which it is ground, and 

 lapped or stoned to the exact clearance required between the punch 

 and the die opening, which, in this case, is .0005 in. all around. 



Fig. 20 — Rough milled blanking 

 punch, solderless cord tip punch 

 and die 



Fig. 21 — Shedder, insert, and per- 

 forator punch for solderless cord tip 

 punch and die 



Fig. 21 shows "A " one set of the perforators for producing the two 

 sharp projections in the cord tip stem, "5" the insert, and " C" and 

 "D" the shedder before and after the insert is in place. The blanking 

 punch also has die holes for the perforators, as can be observed 

 from the general view of the tool in Fig. 12, and these are similarly 

 formed by means of an insert. The perforators, which are working 

 fits in the shedder, are .06 in. wide, Iye in- loi^g and of triangular 

 cross-section. It would, therefore, be very difficult to work out the 

 holes straight and accurate. To facilitate the tool making work, the 

 shedder and punch are made as shown and the insert added. This 

 is a good example of some of the means employed for overcoming 

 difficult tool making problems. 



