You can get many different finishes with tumbling.
For smoothing, use abrasive media in a vibratory tumbler. To burnish, run steel in a rotary tumbler.
Either tumbler needs to be large enough for your pieces to move freely.
The action of either a rotary or a vibratory tumbler is inhibited with too much liquid. If you can, a flow-through process keeps the liquid to a minimum. For a vibratory tumbler, use a compounded deburring liquid. For burnishing with steel, use a burnishing compound. Both are easier to mix from concentrated liquid.
For a poor man’s flow-through, set up a gravity system to supply your tumbler. I used a 2-gallon pail, put a plastic fitting in the lower side, fitted a needle valve in-line, and hooked it onto my tumbler. Drains into a 5-gallon pail. Tumbler sits on a homemade box that straddles the 5-gallon pail. Fair warning, this is not a recycle system, so be sure that you don’t run out of liquid. The amount of liquid should be very low, never like an open hose.
When burnishing very detailed pieces, use stainless pins in your mixed shot. Don’t use them any other time because the pins will often strike the work pieces with the pointed ends, creating a very undesirable pitting or orange peel appearance. If you must try mixing pins with your other stainless steel media, the pins can be removed with a medium strength magnet. I use the kind of magnet sold in fabric stores for picking up pins. If you put a plastic baggie on the magnet prior to picking up the pins, it is easy to get the pins off the magnet by removing the baggie. Yes, I know stainless steel isn’t magnetic — but it is, a little bit. And the pins are very light. There is also a special magnet gun that will pick up the pins.
When filling your rotary tumbler, add liquid to just where you can see it peeking through the steel, never above it.
Highly Textured Surfaces
These are extremely well-suited to processing in a tumbler. If the texture is from etching, it is the only way to get a bright finish without distorting the etch pattern.
File and sand as usual, antique if desired, then run a single vibratory cycle with aqua Clean Cut for 4 hours, then 45 minutes with stainless steel in a rotary.
The whole reason I got in this business of mass finishing is chains. And a tumbler is great to finish them, to say nothing of saving your fingers. I tell students — yes, you can finish chains on a buff, but it’s like working under your car with just a jack. Not a good idea, and you can really get hurt. If you have extra fingers, go ahead. Otherwise — tumble.
Since chains are annealed, first run in steel for 45 minutes, then aqua cones 4 hours, then steel 45 minutes. Then, for planished and forged chains, 24 to 48 hours in buff. The buff removes the haze from the burnishing. I do run gold chains in the combination of gray and green hone, 6 hours each, then the steel and red buff. Nobody can tell they are not hand-finished — except I still have all my fingers.
If you are making loop-in-loop roman chain, tumble all the links prior to assembly. You will have a much brighter result.
Small Work Pieces
String them on plastic electrical ties or non-ferrous wire and fasten the ends securely. Finish as per description for desired finish.
Apply the oxidizing agent about 30 minutes from final abrasive finishing.
Things that are hard to buff like anticlastic bracelets are perfect in the tumbler. Do make sure that your tumbler is large enough to have them move freely in the media.
Pre-Finish Odd-Shaped Pieces
Works especially well for gold. If you have exotic shapes that are very difficult to finish inside bits, run the parts in a fine abrasive prior to final assembly.
Precious Metal Clay
Silver or gold, PMC, PMC+, and PMC3 are easily finished with a tumbler. To brighten and work harden, process in a rotary tumbler with stainless steel for 30 minutes to 1 hour. If you wish to smooth your piece, carefully run for 1 or 2 hours in a lightweight plastic abrasive in a vibratory tumbler prior to final burnishing in the steel. PMC is softer than most jewelry metals, and time to finish is much shorter than conventional manufacturing methods. And yes — really run steel, then abrasive, then steel for a bright finish.