Abstract: Apparatus for bending valve stems of inner tubes used primarily in truck tires which facilitates locating the area of bending contemporeous with readily controlling the bend angle of the stems. An apertured clevis is pivotally mounted on a housing that is grooved to receive a valve stem, with a cylinder and piston connected to the clevis for actuating same with respect to the housing to effect a bending of the valve stem. The housing contains a cylinder and piston for actuating rack and pinion members with suitable indicia provided on the pinion for imprinting upon the valve stem. The cylinder and piston members for the bender and the marker are controlled by an air lock safety system.