A tool has a body with an axially extending cavity containing partly cylindrical receptacles. Each receptacle has an opening facing inward toward the axis. A partly cylindrical cam portion of a jaw fits within each of the receptacles. Each jaw has a workpiece engaging portion protruding from the body. Each of the cam portions has a pair of flat flanks that protrude inward from the opening of one of the receptacles. The flat flanks intersect each other at an inner corner. Each flank abuts one of the flanks of another of the cam members. Each of the engaging portions has an outer surface configured to engage a hole within the workpiece. An increment of rotation of the body relative to the jaws causes the inner corners of the flanks to move outward from the axis and the outer surfaces of the engaging portions to move from a contracted position to an expanded position.