A power driven abrading or polishing tool is provided that includes a motor having a rotor; a carrier part having a shaft and a key extending from the shaft; and an abrading or polishing head attached to the carrier part. The rotor includes an outer body of a first material and a core of a second material having a resistance to wear greater than the first material. The core includes an inner passage with a keyway which receives the key on the shaft of the carrier part such that a rotation of the rotor is transmitted to the carrier part and the head.