38 



ARMATURE CONSTRUCTION 



This would require a pressure of at least 

 45x0-5x10700 



1000 



= 240 tons. 



Of course the quality of the material, and the design and con- 

 dition of the disc 

 and the tool, greatly 

 affect the required 

 pressure. 



We may illus- 

 trate, by an ex- 

 ample, another 

 consideration con- 

 trolling the choice 

 of method to be em- 

 ployed. The com- 

 pound die for the 

 stator punchings of 

 a certain 600 h.p. 

 induction motor 

 cost some 200. 

 Three such motors 

 were to be built, 

 and it was esti- 

 mated that to 

 punch out the slots, 

 one at a time, by 

 index dies by means 

 of two automatic 

 presses, would have 

 taken about twelve 

 weeks for the 

 1,500,000 slots. 

 This would have 

 made it impractic- 

 able to deliver the 

 machinery within 

 the required time 

 without buying 

 additional presses. 

 In many instances, however, the use of automatic punching 

 machines with index dies is suitable, and will in this treatise first 

 be dealt with. The discs may be cut by some such type of circular 



