Abstract: Grooves in an article such as a commutator are filled with a soft brittle material before a grooved surface of the article is cut. With the grooves thus filled, the cutting is performed continuously and smoothly without involving formation of burrs projecting into the groove. The soft brittle material includes a water soluble material which can easily be removed from the grooves by merely immersing the article in water. Preferably, the soft brittle material comprises a sublimable material which is self-vanishing or disappearing as it undergoes sublimation to the vapor state when it is left to stand in the atmosphere.

Abstract: An apparatus for the in situ chamfering of DC motor commutator segments 1 separated by insulating spacers 2 is directly mountable on the motor yoke 62, and includes a frame 32 mounting a reversible drive motor 30 and slidably carrying a reciprocating work table 42. A cutter head 44 mounting a chamfering bit 45 is rotatably mounted to the work table by a pin 43 and is swung out of engagement with the commutator segment assembly 11 during each return pass of the work table, during which time the motor rotor is advanced one pitch by a worm driven roller 53.