A workpiece gripper head comprises a body including side plates interiorly slotted on a longitudinal axis adapted to slidably support a selectively reciprocal rod end. A pair of opposed jaw assemblies are guidably mounted within the body and connected thereto for alternate inward and outward movements in a path at right angles to the axis. Each jaw assembly includes a pair of jaw plates having an angular cam slot and a pair of aligned guide slots at right angles to the longitudinal axis. A series of cam rollers upon the rod end are nested within the cam slots and additional rollers are mounted upon the side walls and nested within the guide slots whereby movement in the rod end in one direction moves the jaws towards each other and movement in the opposite direction moves the jaws away from each other.