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