A material chopper may include a counter shear bar, a plurality of stationary knives associated with the counter shear bar, a shaft, at least one rotor section operatively connected to the shaft, each of the at least one rotor section configured to rotate with the shaft, at least one knife holder in each of the at least one rotor section, at least one knife operatively connected to each of the at least one knife holder, and slots in each of the at least one knife holder, wherein edges of the slot provide counter shear surfaces for the plurality of stationary knives. The material chopper may be added to or incorporated into a harvesting machine such as a combine.