Abstract: A work spindle device having a rotor which allows a workpiece to be fed and ejected quickly and permits the workpiece to be machined simultaneously at opposite ends thereof. A clamp member having collets on opposite ends and a central axial through hole for insertion of the workpiece therein is disposed in the rotor. Each of the collets is insertable in one of a pair of tapered holes defined in the rotor so as to be pitted therein. A spring means normally urges the collets and the corresponding tapered holes into interfitting engagement for clamping the workpiece in the rotor. The work spindle device also has a mechanism for releasing the collets and the tapered holes from their interfitting engagement to unclamp the workpiece from the rotor.