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BELL SYSTEM TECHNICAL JOURNAL 



One of the best examples of a high grade tool needed to make parts 

 within close limits is the compound punch and die shown partially 

 completed and disassembled in Fig. 7, for perforating and blanking 

 complete in one operation the multiple bank terminal strip shown in 

 front of the tool in the illustration. This terminal strip is 36f in. 

 long and has 30 common terminals on each side spaced on 1 j in. centers 

 and 129 perforated holes. The design of the part requires that all 

 terminals and some of the holes be held to within limits of =b .004 in. 



Fig. 7 — Compound punch and die for blanking and perforating multiple 

 bank terminal strip. 



of their correct location with respect to a designated hole at one end 

 of the strip. A limit of ± .004 in. for a single dimension is ordinarily 

 not a difficult one to work to, but in this case the fact that any 

 inaccuracies are accumulative makes it a very difficult limit to 

 meet. 



To make this tool with the required limits of accuracy, it is necessary 

 to make the punch, die, shedder and punch plate sections, as shown 

 in the illustration, so nearly to their exact dimensions that they are 

 practically interchangeable. In fact, the variations are so small that 

 if all the sections were removed from the tool and reassembled in 

 different positions and combinations, the changed tool would not 

 vary more than ± .0002 in. from the previous dimension over the 

 entire length of the sections. In assembling the sections, it is necessary 

 that they be carefully cleaned, as a slight amount of oil or dirt between 

 them would throw the tool outside the desired limits. When it is 

 considered that the tool must be made to much closer limits than the 

 piece part, that all of the 103 sections, as well as the perforators, must 



