The Hammer Mill is used either as a one-step primary crusher for reducing run-of-quarry material to as small as <1-in. size, or as a secondary crusher taking 4~8-in. primary-crusher product down to <¾-in. or finer. Its use as a rock crusher is almost wholly confined to the softer, easily crushable materials such as phosphates, gypsum, barite, asbestos rock, …