That being said, here are a few links I found for building your own ball mill, a rod mills would be build much the same but using heavy rods instead, old truck axles would be a great source for a small rod mill, with a ball mill or a rod mills having different sizes of grinding medium would work better than having all of the same size balls/rods.
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The small and average capacity Ball mills are used for the final grinding of drugs or for grinding suspensions. The maximum capacity Ball mills are used for milling ores prior to manufacture of pharmaceutical chemicals. Advantages of Ball Mills It produces very fine powder .
The ball mill is powered by a fairly robust 12V DC motor salvaged from a junked printer. It had a pulley for a fine toothed belt on it. It was left in place and it seems to drive the heavy round rubber belt well without slipping. The motor was mounted using screws on only one side, which were deliberately left loose.
Large to medium sized ball mills are mechanically rotated on their axis, but small ones normally consist of a cylindrical capped container that sits on two drive shafts . A rock tumbler functions on the same principle.