(1) After commutator surface has been renewed, measure depth of
If this depth is less than 0.25 inch, undercut
mica below surface,
mica with power-driven, mica undercutting tool, using cutter that
Cut to a depth of 0.032 inch
will produce groove 0.052 inch wide.
(2) After undercutting, remove carbon and mica particles with
Remove burrs left by undercutting:
hold strip of
5/0 sandpaper against commutator while armature rotates in lathe at
approximately 2,000 rpm (fig. 5-15).
(3) Set up dial indicator gage, and measure accuracy of finished
The total indicated runout shall not exceed 0.001 inch,
and variations between any two adjacent commutator bars shall not
exceed 0.0002 inch.
Repairing Varnished Surfaces of Housing Assembly and Armature
Polishing commutator surface.