A horizontal grinder is disclosed herein. The grinder includes a grinding structure and upper and lower feed conveyors for feeding material toward the grinding structure. The upper feed conveyor is positioned above the lower feed conveyor such that the material fed toward the grinding structure travels between the upper and lower feed conveyors. The grinder also includes a power source for rotating the grinding structure. A controller is provided for controlling the speed of at least one of the lower and upper feed conveyors in proportion to an operating characteristic of the power source.