A ball mill is a device used to crush metals and chemicals into a fine powder
I have a rather large collection of junk in my basement, and decided to assemble it into something useful.
(I love to juxtapose various chemicals into my images.)
The small 12v motor is slow enough to directly drive the shaft, avoiding the complications of aligning belts and pullies.
The two large wheels are actually casters, which swivel to keep the jug nicely centered.
The jug is a huge 5 gallon container with cenetemeter thick walls designed for storing water.
My first medium consisted of a 1cm diameter steel rod cut into 2cm pellets. It's decent at grinding charcoal and other brittle materials, but it leaves thousands of tiny steel filings coating the inside of the jug.
My current medium is a few dozen steel ball bearings. They work well for grinding metals, but I don't really have enough of them. I'll have to try nickles next.