A tumbler, often referred to as a rotary tumbler, and a vibratory polisher are both types of machines used to polish rocks, but they operate in different ways and can produce different results:
Rotary Tumblers (Tumblers): These machines polish rocks by turning them in a cylindrical barrel. The items to be tumbled are put in the barrel along with the polishing media. Over time, the tumbling action of the barrel rounds off sharp edges and smooths the surface of the rocks. Rotary tumblers tend to produce more rounded finished rocks. The reshaping happens almost entirely in the first step of the tumbling process with the coarsest grit.
Vibratory Polishers: These machines polish rocks by shaking them in a bowl. They work much faster than rotary tumblers, completing a batch of rocks in about half the time. Vibratory tumblers tend to retain the overall shape of the original rock, just smoothing the contours to a fine polish. This is due to the nature of the movement, where all sides and surfaces of the rock are worked almost equally.
Both types of machines use varying sizes of grit to polish the rocks. The choice between a rotary tumbler and a vibratory polisher often depends on the desired shape of the rocks and the time available for the polishing process. Some people even use them in conjunction with one another.