WINDING OF CONTINUOUS-CURRENT ARMATURES 287 



several armatures at different stages during the assembling of 

 the finished coils on the armature, and we shall take the different 

 types of winding separately and deal briefly with each. 



Preparation of the armature body for receiving the coils .- The 

 armature core should be prepared so that the coils can be readily 

 assembled on it with a minimum of damage to the insulation. It 

 is usual to run a file over the sharp corners of the teeth at the 

 surface of the armature to take off all rough edges wherever the 

 coils are likely to touch. Instead of using a file, the corners may 

 be ground off with the aid of a small emery wheel. A convenient 



FJG. 342. Metal Form for Standard Coils (American General Engineering Co.). 



grinder made for this purpose by the Cleveland Armature Works 

 is shown in Fig. 343. It consists of a portable emery wheel 

 driven by a small electric motor and suspended from the ceiling 

 for convenience in handling. Of course such work on the core 

 increases the core loss, and is undesirable from that standpoint. 



It is stated that this tool will work about ten times as quickly 

 as the time taken by hand or with an ordinary file. 



The next step is insulating the armature body. Fig. 344 shows 

 a typical moderate-sized armature insulated and practically ready 

 for winding. The insulation for the slots is cut up from the sheet 

 into strips to the required width in a guillotine or hand shear, of 

 the type shown in Fig. 345. The width of the strips must be 



