Selecting a Rock Tumbler
Almost everyone begins with a small rotary tumbler--that’s because (1) they are so inexpensive to buy, (2) they are so inexpensive to operate, and (3) they conserve your expensive grit & polish. A Lortone 33B twin 3-Lb barrel rotary tumbler would be a great choice for most beginners.
Other Things to Consider
If you would like to analyze further, I recommend you first consider just what kind of rock tumbling you intend to do. If you answer that you want to tumble various small rocks (say ½-inch by 1-inch), either a rotary tumbler or vibratory tumbler will do that very well. If you want to tumble glass (very soft) and rounded stones from a stream, the edge would go to a vibratory tumbler. If you’re new to tumbling and cost is an issue, the nod goes to a simple rotary tumbler with twin barrels. If you want to tumble large stones, say 5-inches in diameter, multiply the rock size by 3.5 to get the rotary barrel size you will need. If you want really rounded rocks, rotary tumblers are the way to go.
Rotary tumblers are very durable (and quiet) and their rubber barrels almost never wear out. The rubber will NOT embed with coarse Silicone Carbide, so you do NOT need to have separate grit-only barrels and polish-only barrels. Plan on a normal batch of agate to take 2 to 3 months to grind and polish. Rotary units begin with 80-grit SiC, then move to 220-grit, then to 600-grit (then, if rocks are soft, to 1000-grit), then to polish.
If angular (not sharp) rocks are okay, vibratory is the way to go. If noise will be an issue, rotary tumblers are very quiet. The quietest vibratory units are made by Tagit, but the cost of “quiet” is that you will likely have to replace bowls more often than a Thumler vibrating tumbler. If speed is an issue, vibratory tumblers will tumble and polish a batch many times faster than a rotary tumbler.
Vibratory tumblers need more tender loving care. The Thumler models are quite noisy, but their bowls last a long time. Tagit models are quieter, but the bowls wear out more often. Vibratory bowls DO embed with Silicon Carbide, so you must always purchase a separate bowl just for polishing. Plan on a normal batch of agate to take 2 to 3 weeks to grind and polish. Vibratory units begin with 220-grit SiC, then move to 600-grit (then, if rocks are soft, to 1000-grit), then to polish.
Higher volume tumbler operators will use 2 or 3 rotary tumblers to complete the rough grinding of Stage 1 and then put the rocks in a vibratory tumbler to finish them off quickly. This practice has two added advantages: first, the rocks will be rounder, and second, it will really increase your vibratory bowl life.
The Bare Minimum Stuff
For a beginner who has no equipment or powders, I would recommend that you purchase the following:
The book (Modern Rock Tumbling), the rotary tumbler of your choice, a quart of Ceramic Shapes, a half-gallon of 80-grit SiC, a Quart of 220-grit SiC, and a pint each of 600-grit SiC, 1000-grit SiC, Cerium Oxide rock polish, and Tin Oxide rock polish. Then add a zoom-spout oiler, a Polish Stick, a Stir Stick, a plastic colander, three pairs of tablespoon measures and an Accufill Ring. These items are discounted in our "Package Deals" section.
If you choose a vibratory tumbler, get rid of the 80-grit SiC, the AccuFill Ring & the Zoom Spout oiler in the list above, and increase the 220-grit to a half-gallon. Then add a pint of Fused Aluminum Oxide Polish. The rest of the items will remain the same. Again, see our "Package Deals" for vibratory tumblers.
Final Note: There are some very cheap rock tumblers on the market which don't work very well and won't last. You can purchase gun cartridge tumblers or the Harbor Freight jewelry tumblers which wear out quickly, due to the fact that their motors are under-sized for rocks. I know many who have purchased old, tired tumblers from garage sales. Our experience has been that most people who do this end up being unhappy about rock tumbling, because they spend all their time working on problems with their equipment, rather than dealing with pretty rocks. In my humble opinion, it is always wise to purchase a quality product from a knowledgeable dealer. Enough said...