CompuServe Thread

Hi, Alex– Welcome to the forum! >> I would like to know if anyone can tell me what abrasives are used in those small rock tumblers (polishers). I have a small one and want to make a larger one, but the composition of the various abrasives is not written on the small packages. Any other suggestions on rpm, cooling etc. would be appreciated. Keep watching this space; while I have not used a tumbler, there are others here who have. They may all be away from their computers during this holiday period. I am repeating your message to make sure they see it when they get back. –Doug

Alex… Silicon carbide in screened grits is the most common "grinding" compound…I most often used three: a combination 60/90 for initial grinding; 220 for a secondary grinding; and 500/600 for "prepolish". There are a great many polishing approaches depending on what you're tumbling. I've tumbled agate and jasper for the most part. Cerium oxide together with some liwuid dish soap is a typical polishing substance, most often used in conjunction with plastic spheres or other types of "buffering" objects (walnut shells). All these compounds are available at lapidary supply stores. There are a number of books about tumbling which go into some detail about tumbling speeds and types of rock which can be mixed in the tumbler (they must all be of nearly the same hardness). One that I particularly liked is buried in the garage at the moment and the title escapes me; I just saw it listed in LJ or Rock & Gem but for the life of me I can't find the listing right now. If you ask at a lapidary supply store I think it has a white cover with a variety of tumbled stones depicted. Typically, cooling isn't an issue with tumbling because the movement inside isn't fast enough to generate much frictional heat. There are nearly as many tumblers as there are backyard engineers. Everything from old automobile tires set on turning rollers to cement mixers have been successfully used. Be aware that the tumbling process does produce gases that can build up pressure and in large (commercial) operations have been know to burst the tumbling barrel. -Russ PS What I ended up with was a "system" of three tumblers. A 10# unit for rough grind. A 6# unit for medium; and a 3# unit for polish…I found that I was sorting a 10# batch and getting about a full 6# "load" that I wanted to advance for the next phase. Then I'd refill the 10# barrel with the remaining stones from the old batch plus new rocks to fill it back up…When the 6# batch was done it usually yielded about one 3# load for polish. Eventually, I had all three going most all the time.