Bench Testing: Armature

Using a digital ohmmeter, determine if armature is grounded by checking for continuity between commutator and core. If ohmmeter shows continuity, replace armature.
Determine if armature is insulated by checking for continuity between commutator and shaft. If ohmmeter shows continuity, replace armature.
Place armature on "V"-blocks. Using a dial indicator, check commutator runout. If runout is more than .002" (.05 mm), use a lathe to repair commutator. If diameter of commutator is 1.13" (28.8 mm) or less, replace armature.
Check commutator to ensure it is free of burnt spots and scoring. If commutator surface is dirty, wipe with cloth. Remove burnt spots with fine emery cloth. If commutator is excessively scored, use lathe to refinish commutator face.
NOTE: Do not use emery cloth on commutator face.
If depth of groove between commutator segments is .008" (.02 mm) or less, undercut insulating material using appropriate tool with sharp point. Undercut until groove depth of .020-.031" (.5-.8 mm) is reached.
If armature laminations show signs of having contacted field coil pole-pieces, check that pole-pieces are tight in field frame housing. Check armature for excessive runout (bent shaft). If armature shaft is bent, replace armature.