Abstract: Milling apparatus for reducing the size of grain kernels or particles by impact with a solid surface as the grain is moved through the apparatus by an air stream created by rotation of a rotor within a stationary casing having an inlet opening at or near the center and an outlet opening at the outer periphery. The rotor comprises a circular disk having a series of elements affixed to a surface thereof in a circular configuration spaced outwardly from the center of the rotor. The elements comprise sections of hollow steel tubing of rectangular cross section or toothed blades so arranged that grain traveling radially outwardly from the inlet to the outlet opening of the casing impact with the elements with a force sufficient to break the grain. The particles may be passed through additional rotor stages, and the particle size or texture of the final product may be controlled by the speed of rotor rotation and the number of rotor stages through which the grain is passed.