Michael A. Terrell Inscribed thus:


Baron wrote:

I've done that with a lolly stick and fine glass paper, then I
discovered the abrasive sticks made just for this purpose.


This was 30 years ago. No internet, and no industrial suppliers in
town.


Similar time frame. Maybe 40... :-)
It was "Hoover" that provided the abrasive stick. The idea was to use
them to quieten down particularly sparky motors. Even though they had
noise suppression capacitors and chokes on the motors they could cause
TV picture break up. People did complain about it as well. I'd being
using the lolly stick for some time before then to smooth the comm.
I'm of the opinion that poor manufacture of some armature left the comm
slightly off centre causing the brushes to bounce and thus arc more
than they normally would.

--
Best Regards:
Baron.