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4. Check the commutator (A) surface. If the surface is dirty or burnt, resurface with emery cloth or a lathe within the
following specifications, or recondition with #500 or #600 sandpaper (B).
5. Measure the commutator (A) runout.
A. If the commutator runout is within the service limit, check the commutator for carbon dust or brass chips
between the segments.
B. If the commutator run out is not within the service limit, replace the armature.
Commutator runout
Standard (New): 0.02mm (0.0008in.) max
Service limit: 0.05mm (0.0020in.)
6. Check the mica depth (A). If the mica is too high (B), undercut the mica with a hacksaw blade to the proper depth.
Cut away all the mica (C) between the commutator segments. The undercut should not be too shallow, too narrow,
or v-shaped (D).
Commutator mica depth
Standard (New) : 0.5 mm (0.0197 in.)
Limit : 0.2mm (0.0079 in.)
7. Check for continuity between the segments of the commutator. If an open circuit exists between any segments,
replace the armature.
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