Abstract: An apparatus for fine grinding material, such as waste automotive tires. The apparatus includes first and second plates mounted within a housing. The first and second plates include respective, opposed inclined surfaces and respective pluralities of generally radially extending cutting elements. Each of the generally radially extending cutting elements define a serrated edge extending above the corresponding inclined surface. The serrated edges on the first and second plates intermesh with one another while the opposed inclined surfaces define a grinding space therebetween that gradually becomes more narrow in a radially outward direction. One of the plates is mounted for rotation and a drive is operatively coupled with the one plate for rotating that plate during a grinding operation.