If you’re reading Hackaday, there’s a good chance you had a rock tumbler in your younger days. Hell, we’d put odds on a few of you having one rumbling away in the background as you read this.

If you’re reading Hackaday, there’s a good chance you had a rock ... rotary tumblers which take a brute force approach that tends to round off the rocks. Anyway, while you could use a motor ...