PRECISION TOOL MAKING 



387 



blanking openings on account of the elongation or "creep" of the 

 material. An error in a tool of this type is detected very easily in the 

 product, and it requires only a very small amount to make the hexagon 

 nut irregular in shape or "lop-sided" with respect to the center hole. 

 It is therefore necessary that the tool maker work to close limits in 

 maintaining the relationship between the perforator and the blanking 

 openings and clipping edge, and the total variation between any of 

 these is not more than .0008 in. to .001 in. It is not only necessary 

 that this accuracy be held on the die section, but also on the punch 

 plate and stripper, in order to insure the proper clearance between the 

 punch members and die openings, which is .0015 in. 



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Fig. 13 — No. 92 solderless cord tip. 



Another example is the shearing, blanking, and forming punch and 

 die shown partially dismantled in Fig. 12, which is used for making the 

 solderless cord tip, Fig. 13. The parts of the tool, as shown in the 

 figure, are A die, B stock guides, C die holder, D liner pins, R finger 

 stop, /^shedders, G stripper plate, i/ punch holder, / blanking punches, 

 J forming punches, K dowel liner pins, L shearing or perforating 

 punches. The blanked strip in the illustration shows the sequence of 

 operations, the parts being first blanked and sheared two at a time with 

 the blanks remaining in the scrap skeleton. The stock then advances 

 until the blanks register with the forming die where the saw tooth 



