Collet chuck for tapered workpieces

A collet chuck for gripping an externally tapered workpiece comprising a body adapted to be mounted concentrically on the front end portion of the spindle of a machine tool, a collet sleeve axially shiftable on said body, said collet sleeve having a plurality of circumferentially spaced, radially resilient fingers thereon, means for shifting the collet axially, a collet expander mounted on the body and cooperating with the collet fingers to grip a workpiece when the collet sleeve is shifted axially in one direction, a front slide and a rear slide mounted on said body for independent axial movement thereon concentric with said collet sleeve, means biasing each slide in axially forward direction, the front slide having an inner peripheral surface adjacent the front end portion thereof which inclines radially inwardly and axially rearwardly, the rear slide having an inner peripheral surface adjacent the rear end portion thereof which inclines radially inwardly and axially rearwardly, said inclined surface of the front slide being of larger diameter than said inclined surface of the rear slide to enable an externally tapered workpiece to be inserted axially into said slides and thereby successively engage said inclined surfaces of the two slides to position the workpiece concentrically on the chuck and a stop mounted on said body in a position to be abutted by the workpiece after the workpiece has been shifted axially rearwardly on the chuck into engagement with said inclined surface of both slides.