Material is fed through the hopper in front of a hydraulically operated pusher which pushes the material under load-dependant control onto the revolving rotor. The material is shredded between the rotor knives and a fixed counterknife. The pusher is fitted with wiper strips which prevent material from entering between the drawer and machine housing. The perforated sieve with varying hole diameters determines the size of the chippings or shavings. The shavings produced can be removed from the machine by means of a suction device or a screw conveyor. As soon as the material in the hopper has been completely shredded, the machine switches off automatically.