"Jon Elson" wrote in message
...
wrote:
Hello Jon;

Yes, I'm familiar with that technique; I use the paper on a glass plate
to lap the surfaces of woodworking plane irons and chisels, etc.

In the case of these aluminum parts, I'm trying to find some way to
power the process and speed it up significantly. These are custom
hardware parts for guitars and basses, so it's not a high tolerance
flatness issue, they just need to look good under plating. Right now,
almost 2/3 of the labor of making the part is in polishing the flat
surfaces. There's got to be a better way tucked away in pro polishing
shops!

I'm wondering whether it's better to do the sanding in a linear form,
as in a belt sander, or in a random-orbit disk form? Maybe either would
work as long as the paper is kept cool and lubricated enough to keep
from loading up. I've thought of, for example, building a small
tabletop version of a woodworking stroke sander, using some standard 2"
wide belts and a coolant flood system. Maybe the finer grits would be a
leather belt and buffing compound?

First, using a lot of coolant (water) with a water-tolerant abrasive will
help a lot. Second, you might want to see how lapping machines
work. A lot like a miniature potter's wheel. I set up one from a
piece of gear I had laying around. I stuck self-adhesive diamond
lapping film to the wheel, because I was doing precision optical
lapping, but the basic idea should work for your use. You'd attach
a sheet of the appropriate sandpaper to the top of the wheel and turn
it on. A water dripper could keep the paper wet. You would hold the
part onto the sheet with the desired force, and turn it so it doesn't
get all the lines in one direction. If you had one wheel for each grit
size, you could just move each part from wheel to wheel as it progresses.
Or, you could do all the pieces on one size before changing
paper to the next grade.

I think you just aren't looking in the right place. These machines
are generically called lapping machines.

Jon

if you're into making machines, i made one of these
http://mrcol.freeyellow.com/grinder/...ap_grinder.htm in a 24" size, but
it can be scaled up or down pretty easily. i got a piece of magnetic sign
material, glued a piece of 1/4" thick felt (both from mcmaster-carr) to it,
then use it as a polisher for glass objects using cerium as the polish.

regards,
charlie
http://glassartists.org/chaniarts