a drum chipper and method providing for air cooling . a drum member , a knife , and a carrier for mounting the knife to the drum member are provided . the carrier comprises an upper clamping member and a lower clamping member for clamping the knife therebetween . the carrier is adapted to mount to the drum member at axially spaced apart mounting positions thereon . the apparatus is advantageously used to chip heat sensitive materials , such as plastic , particularly where the carrier is spaced above and unsupported by the drum member over a span defined between the mounting positions to provide for airflow between the drum member and the carrier .