Making your own homemade rock tumbler lets you turn seemingly ordinary stones you pick up at the beach or along a hiking trail into beautiful works of art. The tumbled stones can be displayed, given as gifts, etched with messages or used as craft supplies. You may find that the stones you pick up outside look a lot like the expensive, commercially available rocks, crystals and stones you find in gift shops once they've been through your homemade rock tumbler. A little tumble makes a big difference.
Drill two holes through the coffee can on opposite sides, about 1/2 inch down from the can's top lip. The holes should be just large enough to thread the ends of the turnbuckle through.
Thread the turnbuckle through both holes.
Replace your drill bit with the spade bit and place the wide part of the spade bit through the middle opening of the turnbuckle.
Mount the furniture wheels on the plywood in two parallel lines of two, all oriented to roll in the same direction and about 2/3 the coffee can's diameter apart.
Place the coffee can on its side, resting on the wheels, oriented so that as the wheels spin the coffee can will rotate in place.
Fill the coffee can with coarse sand and any rocks you want to tumble.
Hold the power drill steady and turn it on. This will turn the spade bit, which in turn rotates the turnbuckle and the coffee can.
Empty the coarse sand out of the tumbler once the rocks are tumbled smooth. Replace the coarse sand with fine grit, insert the now smooth rocks and run your tumbler again to polish the stones.