Tumbling Rocks in A Vibratory Tumbler
Author: Brian Boyle Date Posted:27 April 2015
Vibratory tumbling is a great way to tumble stones, small slabs, cabochons, or preforms in a short amount of time.
Enclosed are a few basic procedures or how to use a vibratory tumbler.
The use of a notebook to keep track of the material you tumbled, the grit steps, days for grit completion, will be of help. Since vibratory tumbling gives such quick results,
CHECK YOUR STONES DAILY.
Use stones of the same hardness in your tumbler.
The tumbler bowl should be 50-75% full when loaded. Use a filler* (see note below) to keep your stones from chipping or spalling.
Vibratory tumbling does not round the stones as much as a barrel tumbler. Some like to use a barrel tumbler for the rough grit stage and this will also extend the life of the vibratory polyurethane liner.
ROUGH GRIND or #80 silicon carbide, abrasive grit stage is for smoothing the stones or smoothing edges from slabs, (wash slabs in soapy water to remove cutting oil before placing in bowl), and add grit at 1 tablespoon per pound of stone in the tumbler. Rule of thumb is an equal amount of water and grit. Slurry thickness is IMPORTANT.
As the stones wear away, the rock dust, moisture and abrasive mix form a slurry which coats the stones. If the slurry is too thick, grinding action will stop. It may be necessary to add more water or sometimes the slurry must be discarded. In that case, completely clean stones, and add grit and water and continue tumbling.
Estimated time for rough grind will be 1-5 days. When this stage is completed, thoroughly clean barrel and lid. Clean stones by rinsing them off on an elevated fiberglass window screen and rinse off with the garden hose and rinse several more times. (Do not clean stones in the kitchen sink or you will clog the pipes.) Grit left in vugs or crystal pockets will contaminate the next stage if not removed.
OTHER GRINDS: The harder the material, the more steps of grinding or grit should be used to get a smooth surface. Stones having a hardness of 6 or more should use the following grind or grit sequence: 80, 220, (400/optional,) 500, (aluminum oxide 800 pre-polish/optional) then polish. From 220 grit stage on, the usual average time for grinding is 24-48 hours. Continue all the grit stages with the same amount of grit and water as before and tumble, wash/rinse off grit, clean barrel and lid, etc. If you have cabochons hand prepared through the 220 grit stage, they may be added to the tumbler at the 400 grit tumbling stage.
FINAL STAGE IS POLISHING: UseTin oxide or cerium oxide in the ratio of one tablespoon of polishing powder for each pound of stones and add water in the ratio of 1/2-1 tablespoon per pound of stone. Add a filler for this stage which aids in thickening the solution surrounding the stones and in addition cushions the load. (FILLERS: hardwood sawdust, maple pegs, small masonite chips, rice hulls, rubber pieces, ceramic media or plastic pellets.) For most hard stones use about 1/4 cup of filler per pound of stone. Obsidians will need 50 to 75% filler.
IMPORTANT: Do not attempt to operate this cycle with mixture too thin. Load must be coated with a thickened "batter" like solution in order to obtain optimum results. Check stones at 8 hour intervals. Agate & quartz will normally polish more rapidly than softer stones. Should the mixture require the addition of solution or water, add sparingly and slowly to bring the mixture to a "thick batter" stage. Approximate time for polish stage is 2-3 days up to a week. When stones have reached the desired polish, (they look as good dry as wet), remove, wash load thoroughly, with a final wash in detergent, rinse and then dry stones with a terry cloth towel.