A Ball Mill
Whatever you use, it must be very sturdy!! These mills must endure heavy vibration and weight loads. The electric motor should be a 1/3 to 1/2 horsepower, capacitorstart, 1725 rpm, 115v motor. You can get one from Grainger using part # 6K758. In my case, I am using a motor salvaged from a washing machine for which I paid 10.