Rock mill or rock grinder.
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Previously:
https://www.homemadetools.net/forum/...3602#post99570
https://www.homemadetools.net/forum/...718#post147960
https://www.homemadetools.net/forum/...830#post129255
https://www.homemadetools.net/forum/...2360#post76209
https://www.homemadetools.net/forum/...1250#post74040
