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ELECTRICAL MACHINERY 



oil; this will produce a high polish. The commutator is 

 then cleaned with a piece of rag and all copper dust is 

 blown from the brushes and brush holders by a bellows. 

 The windings and commutator connections must also be 

 thoroughly cleaned out as the copper dust is likely to 

 produce short circuits. 



FIG. 285. Showing a Commutator-turning Tool in Position for 

 Turning a Commutator True. The device is mounted on one 

 of the brush-holder studs. Crocker- Wheeler Co. 



If the commutator is too rough to be smoothed by 

 sandpaper, a special turning tool is generally used. The 

 tool holder fits on one of the brush holder studs and the 

 commutator is turned down just as though it were in a 

 lathe. (See Fig. 285.) Small armatures are generally 



