Parts Replacement & Testing: Armature

Check commutator to shaft (or core) for short circuit with 1 10 volt AC test lamp. Test lamp should not light, however slight glow may occur due to dampness. Check armature coils for short circuit between windings using an armature growler.
Check commutator for pits, burns or rough surface. If out of round exceeds 0.002" (0.05 mm), or grooves or burned spots cannot be removed with fine crocus cloth, commutator must be turned. Undercut insulation between commutator bars to a maximum depth of 0.024" (0.6 mm).
NOTE: Never use emery cloth or a file on commutator; turn on a lathe only.