starter service

[larry harding]

i grew up around electric motors so starter/generator diagnosis is not too much of a problem, i even have a growler for checking armatures. i remember the motor shops having a ,motorized saw like device that was used to undercut the mica on the commutator after cleaning it up. that i don't have. does any body have suggestions on an easy way to do this short of using a hacksaw blade and doing a not too good of a job by hand?