On Sun, 23 Sep 2007 15:12:19 -0700, wrote:

A while back I posted about the possibility of tumbling long parts in
a mill to give them a finish. I've been experimenting with this
recently, and so far it's worked pretty well.

I went and got one of those cheap rock tumblers from the dreaded HF...
I always feel guilty after I walk out of there, thinking: 'There goes
a few more dollars to China'... But what can you do? Everybody buys
from China in my product field too, which is why I can't afford to buy
American myself.

I went to the pet store next door and picked out a few bags of
different media... Small river pebbles, walnut shells, and corn cob.
So far I've only tried the pebbles, which are basically the small
polished kind, about 1/8" to 3/16" in size. I filled the canister
about 1/3-1/2 full with the pebbles and water, and also added a couple
squirts of orange oil soap. It took a while to get the time down, but
on 6061, it looks like about 2 to 2 1/2 hours is just about right. The
parts come out looking great with a finish that is about equal to your
average fastener. Using the walnut or corn cob would I'm sure improve
that to a high shine. But for mechanical parts, just the pebbles alone
are great. I'm actually surprised how short a time I have to leave it
in there. Harder metals would obviously take longer, but this is fine
for aluminum. Mostly I've been doing 1/4" round pieces of various
lengths, but I also did some 1 1/2" angle brackets. The only real
limiting factor is the size of the container.

So next up is to build a long one so I can do parts about 2' long. I
think a 1/4 to 1/3 HP motor should do. I'll need to work out the ratio
to get the tube spinning at about one rotation per second or a little
faster. I should be able to put about 20-30 pieces in there at a time,
which sure beats polishing one at a time.

Dave

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