I’ve done several videos where I cut out test parts or widgets out of aluminum.  I wanted a good way to knock the edges off the parts and get a good surface finish.  I came up with this very easy to put together DIY homemade parts tumble for my smaller DIY CNC created parts.

A windshield wiper motor form an auto would also work great for this device. You could also connect it to the drum via pulleys or chains to minimize the wear on the motor.  I did this quick and dirty just to test the idea and I think I got pretty good results.  Here I used BB’s (zinc plated) but you could use stones, wood, coins, ball bearings etc.