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BELL SYSTEM TECHNICAL JOURNAL 



with respect to each other that, when properly guided and forced 

 into engagement with sufficient pressure, they will produce a uni- 

 form permanent change on the material placed between them. 

 Punches and dies are made to perform a variety of operations, such 

 as cutting or shearing parts from strip stock, commonly termed 

 blanking, perforating or piercing holes, drawing, forming or bending, 

 stamping, embossing, etc. In many instances two or more operations 

 are combined in one tool, as, for example, a perforating and blanking 

 punch and die, which cuts the part to its required shape and also 

 perforates the required holes. Multiple operation tools may be con- 

 structed in many different ways, depending on the particular require- 

 ments of the part to be made. Typical illustrations of punches and 



Fig. 1 — Compound punch and die of the liner pin type assembled. 



dies for accurate work are shown in Figs. 1 and 2. The former shows 

 a compound punch and die of the liner or guide pin type assembled, 

 and the latter shows a partially disassembled tool of the sub-press 

 design, in which the moving member is completely enclosed and 

 guided by the housing. 



The compound type of construction mentioned in the preceding 

 paragraph, which perforates and blanks the part complete in one die 

 position and one stroke of the press, gets its name from this feature of 

 performing a compound operation in one die position, and is generally 

 used where very accurate parts, practically free from distortion and 



