wood in a rock tumbler ? - The SawdustZone
How about a rock tumbler that's mostly full of sand, and then add a few of your parts. The parts themselves knocking against each other aren't going to give you the action you need, but maybe larger media will.
tumbling machine to round sand granules edges
tumbling machine to round sand granules edges. How to Make Tumbled Stained Glass | eHow . Pour a cup of sand inside an ice cream making machine tumbler. If using a Cool Whip size plastic container, ...