A machine for the wet or dry fine crushing of ore or other material. The three main types are the ball, rod, and tube mills. The mill consists of a rotating cylindrical drum; the ore enters one hollow trunnion and the finished product leaves the other. Modern practice indicates ball mill feeds of 1/2 in, 3/4 in, and 1 in (1.27 cm, 1.91 cm, and 2.54 cm) for hard, medium, and soft ores respectively and the products range from 35 to 200 mesh and finer.