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The electric motor is mounted vertically to the bottom of the
bowl mounting plate. An off-balance counterweight is mounted on the
motor shaft and as it spins, it causes the mounting plate and bowl to
rock back and forth very rapidly. This causes the stones to vibrate
against each other rapidly and the carefully rounded inner shape of the
bowl causes them to roll over top of each other. The abrasive grit is
carried up between the rocks, grinding off the rough edges. Once the
rough edges are ground down, the rocks can be polished to a glossy
finish, also using the vibratory tumbler.

The bowl mounting plate is mounted to carefully chosen flotation
springs, allowing it the right amount of movement for optimum
vibration and tumbling.

The bowl lid, mounting plate, tumbler base, and base cover plate are all
fiberglass reinforced for maximum strength. The bowl is made of
Durometer 90 Shore A urethane for maximum abrasive resistance. This
is a material similar to what is used in roller blade and skateboard
wheels. Bowls are a minimum of ½” thick in all high-wear areas.