Component Testing: Commutator

Inspect commutator for roughness. If surface is pitted, stepped or grooved, it should be lightly sanded with No. 400 sandpaper. Check commutator for out-of-round.
If out-of-round is more than .002" (.05 mm), turn the commutator on a lathe until out-of-round is within specification.
Wear or cutting limit of commutator is 1.08" (27.5 mm) on Mitsuba starters, or 1.14" (29 mm) for all others.
If worn less than .008" (.20 mm), insulating mica should be undercut to a depth of approximately .015-.031" (.40-.80 mm) on all models.