Abstract: A radially adjustable rotary cutting tool such as a rotary reamer or the like. The tool head has a generally cylindrical body with a shank at one end and a radially slotted cutting head at the other end. The cutting head has a central axially extending threaded bore adapted to receive a threaded expansion element that may be used to radially expand or enlarge the cutting head when turned into the bore. The cutting head has an inner core portion formed of a low to medium alloy carbon steel and an annular outer portion formed of a tool steel metallurgically bonded to the core portion to provide a unitary composite structure. The annular outer portion has a plurality of circumferentially spaced longitudinal flutes formed therein to define integral longitudinally extending radially adjustable cutting surfaces.