Rotary tumbler polishing for aluminum?

I have tons of 1/4" and 3/16" aluminum round parts that I have to polish all the time. These range in length from 2" to 24". I've been thinking for months on how I can do this faster. I'm wondering what everybody thinks about using some sort of rotary media tumbler to do this? Would the parts get lodged up because they're long? I've searched for an affordable machine that could do this, but most affordable ones are the smaller pot shaped vibrating kind, or a rotary drum that's too short. Maybe I could build one myself? Also... If there's threaded holes in the parts, what media type would be good enough to polish the outside, but not ruin the threads in the holes? Or would it just be better to drill and tap after polishing? These don't have to be polished to a mirrored surface... Just an even brushed type look is fine.
Thanks for any advice,
Dave

On 20 Apr 2007 18:16:25 -0700, snipped-for-privacy@aol.com wrote:
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=========Given the high L:D ratio you have a good chance of bending the parts by tumbling. Aluminum only compounds the problem.
Good luck with a challenging problem and let us know how you make out.
Unka' George ===============When we are planning for posterity, we ought to remember that virtue is not hereditary. Thomas Paine (1737-1809), Anglo-American political theorist, writer. Common Sense, ch. 4 (1776).

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I've played around with tumbling various smaller aluminum parts and I've never really been satisfied with the result. Have you considered sand blasting or bead blasting?
Jerry

On 20 Apr 2007 18:16:25 -0700, snipped-for-privacy@aol.com wrote:
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There's considerably more to know about this than one might suspect. Sending them out may be the lowest-cost and best-result approach.
One outfit that does this sort of work is Deburring Inc in St. Paul MN. They have huge rotary tumblers and they have decades of experience on what media to use and how long to tumble to get the desired result and finish. They've done everything from snowmobile skids and cellphone antennae to heart valves and SS hip joints.
I know about them because the guy who started the company was a good friend and fishin' bud of mine. He retired and sold the company to an employee in the early '90s. Far as I know they're still doing well.

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What I use for deburring with ceramic media:
http://www.pyrotechniques.org/dwilliams/mill/mill.html
Which is a design popularized by the rigorous analysis of Lloyd Sponenburgh.
You can spin just the mill jar with a lathe, instead of building the whole mill, but lathe motors and bearings are expensive to wear out this way if you have a lot to do.

We use a couple of older vibratory tumbler machines from www.royson.com, like their 3C but about 1/2-2/3 the size, and angle cut cylinrical ceramic media in a couple of sizes (1/8" and 1/4" dia), on both 304 stainless steel and aluminum. We do a lot of 6061 1/4" diameter 6" long round rods (ends drilled and tapped and an e-clip groove near each end) and never have a problem with bending. As you tumble, the surface goes from a few random very shallow divots to lots of divots to uniformly smooth with slightly rounded edges and a somewhat mottled surface appearance, in a total of about 20-40 minutes for the aluminum rods. Naturally the stainless stuff needs more agressive media or more time. We get various 1-4" sized 16-20 ga 304SS parts cnc punched by a sheet metal shop so there are little tits every inch or so along the edges, and the tumbler smooths these right out. They are still there but you can slide your fingers along the edges with no danger. These are internal brackets hidden from sight in our finished products so we don't need to spend the time with a grinder or scotchbrite wheel to really smooth the edges and make them pretty, so tumbling is an efficient way to deburr them. With our media and times the surface is smooth to the touch but is not polished to any kind of really bright finish (although the stainless does come out brighter and shinier than the aluminum), but with finer media and more time you should be able to get much brighter finishes.

On 20 Apr 2007 18:16:25 -0700, snipped-for-privacy@aol.com wrote:
Hi Dave,
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Not sure about the long parts, but I have had good success with aluminum using 1/4" dia round ceramic media about 3/4" long with a non-foaming cutting fluid in a bullet case tumbler. I used 1 cup of fluid in the largest Midway tumbler.
After 2 hours, they come out nicely deburred and looking sort of randomly scuffed but about 5 minutes in a water and 10% Lye mix turns them into very clean matte finished parts. I had to make a about 200 spacers for a local company some time back and they were well pleased.

Thanks for the info everybody... I think for the heck of it, I might try making something similar to what Richard posted. I actually already pictured something kind of like that in my mind. Maybe have a few different sizes of tubes that you could lay on there, depending on the part sizes. Chuck some walnut chips in there and see what happens. If it doesn't work well, no biggie.
Dave