1/3/2024 0 Comments Rock tumbler grit![]() Hobbyist tumblers typically sell for between $70 and $300, depending mainly upon their size. Model B tumblers have been manufactured by the Tru-Square Metal Products Company since the 1960s and many of those early tumblers are still in reliable use today. It has a metal barrel with a rubber liner that is large enough to process about ten pounds of rock. It is one of the larger and best hobbyist-grade tumblers. ![]() Hobbyist Rock Tumbler: The tumbler shown above is a Thumler's Model B rock tumbler. After following this procedure, the rocks are usually transformed into brightly polished stones. Then the rocks are tumbled for one final week with water and a rock polish. The rocks are typically tumbled for one or two weeks in coarse grit, one week in medium grit, and one week in fine grit, with a thorough cleaning of the rocks and the barrel between each grit size. Tumblers that operate this way are known as "rotary tumblers." This action wears sharp edges off of the rocks and smoothes their surfaces. As the rocks tumble, they grind against one another with particles of the abrasive grit caught between them. The barrel containing rocks, grit, and water is placed on a motorized machine that rotates the barrel to tumble the rocks that are inside. The grit is often labeled "coarse," "medium," and "fine," similar to the different grades of sandpaper. The abrasive grit is a granular material similar to the grains glued onto sandpaper. The most popular tumblers have a barrel that is loaded with rocks, water, and abrasive grit. Visible in this image are fancy jasper, tiger's-eye, carnelian agate, sodalite, banded agate, tree agate, banded amethyst, eye agate, zebra jasper, blue lace agate, blue chalcedony and more. I guess it works like a tumbler but in two dimensions only.Tumble-Polished Stones: Some examples of nice tumbled stones. This is a small vibrating table with a lip which holds a thin layer of water and grit. The rough shaped piece of slab was attached to a dop stick with some sealing wax so you can present it to the grinding wheel without losing your fingertips! There is also a flat lap machine to polish one face of a large stone. These were used to make cabachons for use in jewellery findings. ![]() Other gear I inherited was a diamond saw to cut slabs and a bench grinder with different grades of wheel including a buffing wheel for polishing. ![]() Now I’m retired I intend to drag the old tumbler out of the shed and get it going again again with some of my choice finds. Sixty years later I still go to that same beach at low tide and often find several agates if big seas have moved the sand cover and the stone beds are exposed. She used tin oxide as the final polish after the last (carborundum?) grit stage. The finished results were beautiful, especially the hardest stones like the agates. I don’t know how essential this was, I just wanted to put it out there. Occasionally she “burped” the containers by stopping the tumbler, removing the container, briefly unscrewing the lid to release any pressure buildup, retightening the lid and starting the tumbler up again. This also helped in reducing the amount of material lost. The coarsest grit stage could be reduced or omitted. Also, as beach stones can be quite smooth from the natural tumbling effect that has occurred from wave action, selecting the smoothest ones for a particular batch shortened the time required to tumble them. She found that a having variety of sizes of stones in each batch worked better. Collider? Did you mean colander? My mother became interested in lapidary back in the 60s and tumbled beach stones (mainly agates) she collected at low tide near her home (Mid North Coast of NSW, Australia).
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