Parts Replacement & Testing: Commutator

If condition warrants, carefully polish commutator with a strip of fine glass paper. If surface is scored, rough or burnt, dress with lathe just enough to remove defective area. If out-of-round exceeds 0.012", commutator must be turned. After turning, out-of-round must not exceed 0.004". Check mica depth and file off mica if depth is less than 0.008". Correct depth is 0.020 - 0.032".