Ball mills are commonly used in the manufacturing of cement and finer grinding stages of mineral processing. Typical type of fine grinder is the ball mill. 'Rod mill' is also used as a synonym for a slitting mill, which makes rods of iron or other metal. Rod mills are less common than ball mills for grinding minerals. The rods used in the mill, usually a high-carbon steel, can vary in both the length and the diameter. However, the smaller the rods, the larger is the total surface area and hence, the greater the grinding efficiency.
Rod mills are very similar to ball mills, except they use long rods for grinding media. The rods grind the ore by tumbling within the the mill, similar to the grinding balls in a ball mill.