I was taught that on motors as a young boy. One thing to clean out
if still undercut are shavings of metal. All of that cleaned out.
Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
"Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer
TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Originator & Charter Founder
IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com/

On 9/25/2010 3:42 AM, RS at work wrote:


J. D. Slocomb wrote:


Interesting. I was taught to always undercut the generator armature
and never undercut the starter.


Seems to me that any motor or generator should have the mica
undercut. As I understand, the reasons are that the undercuts catch
bits of stuff and keep it from piling up behind the brushes, and if
the mica is not undercut, as the copper wears the mica woulld then
stand proud and cause the brushes to jump.

I have heard some folks say they never do more than a quick polish
with sand paper, but if you look at a new armature the mica is always
undercut, also on the repair manuals that publish specs on the
commutator they have minimum diameter and undercut depths (Toyota as
an example I recall.) Also see:

http://www.tpub.com/content/misc_man...242-350037.htm

Roger Shoaf