Abstract: The preferred embodiment of the invention disclosed herein includes a housing having an inlet opening and an outlet opening, the latter being in communication with a discharge chute. Inside the housing a cutter bar is rigidly mounted adjacent a rotor assembly including a plurality of cutting blades which cooperate with the cutter bar for cutting brush, that is, tree limbs and similar debris, into small chips. The brush is fed to the cutter bar through the inlet opening and the chips are discharged through the outlet opening into the discharge chute where they are carried away in a high velocity air stream provided by a blower unit. Further included is inertia means mounted for rotation with the rotor assembly whereby the rotor assembly can be rotated at lower speeds while assuring that the cutting blades exert sufficient force to adequately cut the brush.