The present invention relates to a single shaft rotary grinder with an improved cutter and combination "comb" rotor and counter knife configuration for reducing film, fibrous material and other material which has a tendency to wrap around the rotor, rubber, solid plastics and wood. Reducing this type of material, such as plastic film, into small pieces has been problematic. This invention provides one or more comb shaped counter knives and a rotor having a plurality of geometrically shaped cutters mounted in a plurality of partial or full rows longitudinally along the rotor. The comb shaped counter knives and the rows of cutters work in cooperation to reduce film and other material into small pieces.