A crusher is a machine designed to reduce large solid chunks of raw material into smaller chunks. Crushers are commonly classified by the degree to which they fragment the starting material, with coarse crushers not reducing it by much, intermediate crushers fragmenting it much more significantly, and grinders reducing it to a fine powder.

Impact crushers involve the use of impact rather than pressure to crush material. The material is contained within a cage, with openings on the bottom, end, or side of the desired size to allow pulverized material to escape. This type of crusher is usually used with soft material such as coal, seeds, or soft metalic ores.