44 



ARMATURE CONSTRUCTION 



is illustrated in Fig. 35. The principle of the " German " type is 

 shown in Fig. 36. The punch is mounted firmly in a solid piece, 

 and can thus only penetrate to a short distance below the upper 

 surface of the die. 



FIG. 34." Bliss " Double Die. 



When slots are to be provided on the inner periphery of a disc, 

 as in the case shown in Fig. 37, it is sometimes the practice (when 

 an index die is employed) to first punch the slots, and afterwards 

 cut out the centre on circular shears. Fig. 38 illustrates how, 

 without making another punch, a deeper slot may be obtained than 



FIG. 35. Compound Die for Armature Disc. 



that for which the punch has been proportioned. Such make- 

 shifts are, of course, only economical in special contingencies, and 

 involve two operations with consequent loss of time. 



Fig. 39, reproduced from Frucht's article, illustrates a punch 

 which cuts both slot and a corresponding portion of rhe periphery 

 at each stroke. Frucht recommends this as far preferable, 

 largely on account of greater exactness in the cutting of the 

 periphery than is obtainable by circular shears, arid states that 



