The shredder has an intermediate gear system which enables the output of the drive motor to match the type of refuse being cut up by increasing the torque at lower speed when thick material is processed. Material to be shredded is entered through a feed hopper (25) and delivered to a helical cutter (15) and a stripping blade (22), the chopped material being discharged through the outlet (26). The cutter is driven by an electric motor (21) and gearbox (32) which contains at least two selectable gear ratios providing different torque values. These gear ratios may selected manually or automatically when heavier material is fed to the cutter.
