Abstract: Method and apparatus which combines centrifugal and rotary-abrasive forces for rupturing air-carried granular material, such as cereal grain, which is then reduced to a desired (variable) screen size or powder. Such product may be as finely pulverized as flour or may simply consist of mixed grains which are reduced to a uniform particle size suitable for pelletized animal feed. Inorganic material such as particles of talc, clay, kaolins, earth pigments, etc. can be similarly processed. Power driven, hollow, cylindrical rotor has circumferential series of axially directed, radial outlets which permit easy passage therethrough of the axial granular flowstream to a surrounding channel or raceway formed by a tubular screen spaced radially outward from the rotor outlets.