a machine for chopping polymers , and in particularly elastomeric materials such as tires , into uniform small size particles through the use of a rotating cutting head having teeth that have side cutting edges generally perpendicular to their outer end edges , which are parallel to the axis of rotation , and interfit with stationary teeth formed in complimentary shape . the cutting head is used in combination with a material infeed mechanism that maintains a steady , positive feed of material to reduce the elastomeric material into uniform small chunks that can be used for fuel , or otherwise more readily disposed than the present large size tires or similar articles .