"Fred Abse" wrote in message
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On Fri, 02 Mar 2012 21:48:04 -0500, Oppie wrote:

Be careful not to cut too much at a time as the torque drag might twist
the commutator on the shaft. Also watch that you don't get too close to
where the wires are attached to the commutator.

You need high speed (~200 ft/min) and a *very* sharp tool. Commutators
are a bitch to machine to a decent finish without ripping the segments
off..

Cheap commutators sometimes have very thin segments, maybe .025" thick.

When in doubt I use as close to a zero rake as possible to avoid pulling out
the copper bars. Most of the motors I've worked on are pretty old and they
didn't skimp on the thickness of the copper. I would use a pointed cutting
tool and a really slow feed rate to get minimum cutting forces. Last pass
would be with a more rounded tool just to smooth it out and finally the fine
grit to polish it out.