Component Testing: Commutator

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 1.22" (31.0 mm) for Cressida and 1.14" (29.0 mm) for all others.
If worn to less than .008" (.20 mm), undercut insulating mica to a depth of approximately .008-.024" (.20-.60 mm).