a vehicle tire carcass or refuse shredder including a downwardly tapered feed hopper widening at the base directly overlying a stationary toothed rack and a rotary cutter assembly , the latter comprising a plurality of disk - like cutters interdigitated with the rack teeth . the cutter disks each carry cutter bits at 180 ° spacing , each with obliquely angled leading cutting edges and sloping rearwardly and radially inward from each of said leading cutting edges . the side edges of the cutter bits cooperate with the adjacent rack teeth to shear off the flaps or chunks of rubber or other material being gouged from the tire carcasses or other refuse items by the pointed tips of the cutter bits .