For nearly all electrical points/contacts, I try to avoid any
abrading/cutting actions that will create clearly visible scratches. Files
and sandpaper-type abrasives tend to leave fairly rough surfaces.
I'm aware that there are numerous makers of tools called "points files", but
they're kind of counterprodutive.
Very fine emery likely exists, but I haven't encountered any that I would
consider to be of powder consistency.

To me, using something that results in a rough surface on switch contacts,
evokes an image of two combs as the contact surfaces with high peaks between
valleys.
Getting something to run briefly, or for evaluation purposes is one thing..
but using abrasives on contact points shouldn't be a regular service
practice, IMO.

FWIW, when contacts have become pitted, they should be replaced, as the
gradual crown shape which helps suppress arcing has been compromised.
Generally, they will continue to erode at an advanced rate, as the surface
plating/coating has likely been burned away.
For a motor that only sees infrequent use, the erosion is likely to go
unnoticed until it eventually fails to start properly.

If I can burnish the surface with a hardwood stick dipped in deoxider,
that's about as cautious/safe as one can be with the precious metal surface
coating.

I can hardly resist buying a decent looking used motor, but my habit has
always been to disassemble used equipment before using it. A little cleaning
and oil can go a long way toward having a reliable motor when a future need
arises.

Lately, I've been trying an ultra-fine crocus cloth for various cleaning or
polishing tasks with good results. The coating on the cloth is a very fine,
powdered material. In contrast to common emery grades and other abrasives
which use granulated materials, noticable scratches aren't created by the
very fine coating.

I've read comments regarding replacement of start switch contacts over the
years, with high silver content pieces, and I think there may have been a
mention of a source of appropriately-sized new contacts not long ago, but I
don't remember if it was in RCM or the SER sci.electronics.repair group.
There are lots of sources for heavy duty, high current relay contacts as
commonly available repair parts, but I suppose that motor switch contact
replacement has often involved a bit of improvising.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Gerald Miller" wrote in message
news On Tue, 7 Jul 2009 23:13:01 -0400, "Wild_Bill"
wrote:

Although I haven't needed to try it, there have numerous reports of new
contacts being installed on the switch leaves of older motors.


I have, on numerous occasions, touched them up with emery cloth.
Gerry :-)}
London, Canada