Now you know why professional quality polishing is so expensive.

You need a fairly hard backed abrasive to avoid dishing holes and making
ripples. Try a pneumatic orbital sander, hard rubber pad, waterproof
abrasive paper, soapy water as a cutting fluid and lubricant. This should
allow you to use up the paper without loading it up and making scratches.

Randy



wrote in message
oups.com...
Hi guys;

I'm looking for some ideas from any of you with experience in metal
polishing. I often make up aluminum parts which need to buffed out to a
level of perfection that will look good under show chrome plating. A
typical part, like a couple I made up this afternoon, is made from
0.090 6061 plate, about 3" x 4" with a milled opening and a dozen
various sized holes.

The problem is, what's an efficient way to get the scratches out of the
flat surface and bring it up to a mirror shine? The last part is easy.
Once the surface is up to about 1500 grit level, it's no problem to
buff it out with a sewn cotton wheel and tripoli compound. How do you
get from scratches to 1500 grit while keeping the surface flat and
even, without excessively distorting the holes and openings?

Right now, I'm hand rubbing the surface with a hard rubber block and
various grits of emory paper. I start with 320 and go through 500, 800,
and 1500, using drops of WD-40 as a lubricant. This works pretty well,
but it's very tiring and takes way too much time. I need a power method
of doing this.

I've tried many types power wheels, such as hard felt buffing wheels,
Norton "finishing" wheels, Scotchbrite flap wheels, etc., and haven't
found anything that works for this. It seems that any wheel that's firm
enough to cut will tend to leave waves and ripples. Softer wheels with
coarser compound would distort all the edges of the openings and holes.
I've tried using emory paper on an electric "detail" sander (with the
recipricating triangular pad), but that just loaded up the paper
instantly and added more scratches.

Any ideas? I'm thinking of a miniature version of a random -orbit
sander, with a 1" dia rubber pad, turning about 60 rpm, using various
grits of lapping paste. Maybe I could rig up a small random orbit head
on a drill press?

Thanks!
Bruce Johnson
Johnson's Extremely Strange Musical Instrument Co.
Burbank, CA