A ball mill, a type of grinder, is a cylindrical device used in grinding materials like ores, chemicals, ceramic raw materials and paints. Ball mills rotate around a horizontal axis, partially filled with the material to be ground plus the grinding medium.
A ball mill consists of a hollow cylindrical shell rotating about its axis. The axis of the shell may be either horizontal or at a small angle to the horizontal. It is partially filled with balls. The grinding media are the balls, which may be made of steel , stainless steel, ceramic, or rubber.
Here you can see an overview of the ball mill with the drum removed. Construction is super simple. Just three pieces of wood plank banged together to make a platform for mounting all the parts. The platform is made from a 1X10 wooden plank 14 inches long.