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DIY Rock Tumbler

Finding impressive rocks is just part of the draw of rock collecting. Most rock hounds own a rock tumbler of some kind, designed to wear down the rough edges of a rock so that it becomes smooth and polished, revealing its inner patterns. Rock-tumbling hobbyists add grit, or rough gravel, to the tumbler before adding their collected rocks. Then the tumbler is run for several hours and sometimes overnight. Rather than purchase an expensive rock tumbler, many handy rock hounds make one themselves.

Supplies
- A rock tumbler is a simple machine made from a few basic parts. The tumbler should be big enough to hold a pound or two of rocks. It must be either metal or heavy plastic to withstand hours of harsh motion--an empty coffee can is a perfect tumbler. You'll also need a small rotary motor--choose one with no more than 30 rpms--and a drive belt. Finally, pick up some furniture or skateboard wheels and a heavy base board to support it all.
Assembly
- Mount the wheels to the baseboard so that they can support the tumbler. It should rest an inch or two above the baseboard. The motor goes on the opposite end of the baseboard. Attach the drive belt from the motor to the tumbler, and ensure there is nothing to impede the belt from turning. When the motor turns on, the belt rotates the tumbler while the wheels keep it in place and allow it to spin for hours.
Modifications
- You can modify a do-it-yourself rock tumbler using the same principles. Try making a large tumbler that can handle up to 20 lbs. of rock by using a 5-gallon plastic paint can and larger motor. If you have electrical experience, you can convert the motor from a used appliance, such as a food processor or a hand-held drill--the motors are just the right for the job and you'll have the added bonus of controlling the speed.

Rocks & Minerals