A closed steel cylinder one-third filled with rods of about the same length as the cylinder and 1–2 inches in diameter. As the cylinder rotates, the rods roll over one another, exerting a combination of impact and grinding action on the charge. It gives a product of 50–60 mesh with a minimum of fines. Rod mills are used for pulp grinding in the paper industry and for size reduction of ores, minerals, metal powders, etc.