I have a little experience with hand polishing, but none with tumblers. Is there any way to get a mirror, or close to mirror finish with just a tumbler? I know IF it is possible, it would probably take 3 or 4 steps (media), and probably several hours(over 24?). But I haven't found any info stating exactly what kind of finish tumbling can actually achieve.
Or could tumbling just be used as a prep for hand polishing? Can it remove cutter 'swirls'? Or maybe even small scallops/cusps?
Getting a mirror finish on aluminum in a vibratory machine requires a couple different media......first use fine grit plastic triangles for 24 to 36 hours. Then use rouge treated walnut shells for another 36 hours. The part has to have smooth surfaces when it goes it the machine. You could use a more agressive media initially, but as it cuts away mill marks, etc it will also be eating away at the other features of the part. Vibratory polishing isnt selective. On turned parts where the proper aluminum-specific inserts have been used for machining, the surface will be sufficiently smooth with no hand prep. Most milled parts require some sanding, and a small vibratory sander works well....better IMO than hand sanding and not nearly so tiring. I've got a couple vibratory finishing machines in my shop, but after fooling around with polishing aluminum parts in them I decided it was too much of a hassle. Here's a part I make. Once the sanding is finished, the whole thing can be buffed out in ten minutes. It's a nasty job, but it makes stuff purty
Any idea as to how much material a more aggresive media will cut from everything? If the parts are thrown in with sharp edges, when a slightly (.01-.03) radiused edge is perferred, would it achieve that? And does it remove material uniformally? If it's only .003-.005 overall surfaces and rounding sharp external corners, I think that would be acceptable.
Would you be able to go straight from tumbler to buffing wheel?
It will attack all edges much more quickly than flat surfaces, much like a sander will when you run it across an edge. How much material gets removed is a function of time and the agressiveness of the particular media, and has to be determined via trial and eror for a particular part. Left long enough, the part will disappear. The learning curve on polishing isnt too steep, but you just have to do it to learn what works and what doesn't.