Abstract: A method is described for assuring concentricity of a gear's pitch circle with its axis, the pitch circle having a non-constant radius about the axis. The method comprises the steps of: determining the gear's pitch circle and its position of maximum radial offset from the gears axis; positioning the gear in a chuck having a plurality of simultaneously movable jaws, the chuck having an axis which is continually concentric with respect to its jaws as they move, the position of maximum radial offset being positioned adjacent a chuck jaw so that when the jaws are moved to grip the gear, the axis of the gear is offset from the chuck axis by action of the jaws on the gear; placing the chuck and gripped gear in a machine tool adapted to machine the gear concentrically with the chuck's axis; and operating the machine tool to remove sufficient material from the gripped gear to bring the gear's axis into concentricity with the gear's pitch circle.