PRECISION TOOL MAKING 



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with clean-cut edges, are to be produced, and particularly where thin 

 stock is used. It is also preferable to other types of tool construction 

 when the part is irregular in shape or is to be produced in large 

 quantities, because of the uniformity of product, high speed at which 

 it can be operated and because of its long life. Where small holes are 

 to be perforated, the compound type is often advisable due to the 

 fact that the perforators can be supported more substantially, with 

 reduced breakage. 



Fig. 3 is a cross-sectional view of one of the standard designs of sub- 

 press compound tools illustrating this type of construction. As its 

 name implies, the sub-press type is a practically self-contained press 

 which is placed, assembled, in the power press. As will be noted 

 from this figure, the compound type of tool has the perforating punches 



Fig. 2 — Sub-press compound punch and die partially disassembled 

 to show construction. 



L located inside the blanking die N, and supported by the shedder Af . 

 and the die openings for the perforators inside punch P, which is 

 fastened to the base H of the tool. In operation, the base H is 

 mounted on the bed of the press and the cap adapter A, which is 

 attached to the plunger D, is fastened to the slide or ram of the press. 

 The stock is fed over the stripper and the die N descends, thus 

 depressing the stripper and causing the shedder M to recede into 

 the die N. As the shedder is backed up by a heavy spring C, the 

 metal being blanked is held under pressure between the shedder and 

 the punch P so that this type of construction fabricates thin sheet 

 metal under conditions which insure the best results. As the down- 

 ward movement progresses, the blank is cut from the stock and the 

 holes perforated. The slugs forced out by perforators L drop through 



