ARMATURE LAMINATIONS 37 



of the plate in mm., and if p = perimeter of the cut, also 

 in mm., then 45 x t x p = required pressure (minimum) in kgs. 

 Thus, to cut from a sheet of 0'5 mm. thickness one of the plain 

 discs of 990 mm. diameter (Fig. 17), there would be required 

 a pressure of at least 



45 x 0'5 x 990 x TT = 70,000 kgs. (70 tons). 

 If, instead of a plain disc, it were required, by means of a com- 



FIG. 23. 150-Slot Armature Stamping from Compound Die. 



pound die, to punch from 0'5 mm. thick sheets, the discs shown 

 in Fig. 23, which have an external diameter of 990 mm., an 

 internal diameter of 500 mm., and 150 slots, each 20 mm. deep, 

 then the perimeter amounts to approximately 

 990 x 7T + 500 x 7T + 300 x 20 



500 XTT = 1570 

 300x20 = 6000 

 Total perimeter =10680 mm. 



