Abstract: A machine tool having a work spindle with an electrically actuated clamping unit including a three-phase motor with a stationary stator. The motor is supplied with electricity from a control unit operating with frequency conversion, and the control unit is alternatingly also used for triggering a spindle drive motor. A sensor detects clamping force applied to a workpiece, and produces a signal used to reduce motor speed of the three-phase motor until a predetermined clamping force is achieved.

Abstract: In the clamping device a clamping head rigidly attached to the rotating spindle is provided between the rotating spindle and the tool holder which has a plurality of adjustable clamping pieces for holding the tool holder on the clamping head. A clamping rod penetrating the clamping head is provided for the tool holder in the hollow rotating spindle. This clamping rod is slidable axially under power operation, is coupled with a central clamping member of the tool holder and is rotatable relative to the rotating spindle. This clamping rod is couplable and uncouplable with the clamping member by rotation. A clamping pipe which is guided axially slidably and nonrotatably relative to the rotating spindle moves and adjusts the clamping pieces. The clamping rod is engaged in the rotation direction with the clamping pipe by the gear unit which converts the axial motion of the clamping pipe to a rotation of the clamping rod.

Abstract: A rotatable chuck workpiece for a power driven threading machine is disclosed comprising a tubular spindle having front and rear ends and front and rear workpiece engaging jaws respectively at the front and rear ends. Each front jaw is connected to a corresponding rear jaw by a rod to which the jaws are rigidly attached, and the rods are mounted on the exterior of the spindle for rotation therewith and for pivotal movement relative thereto. A drive plate at the front end of the spindle is mounted coaxially thereon for pivotal movement relative to the spindle and is provided with drive pins interengaging with slots in the front jaws, whereby pivotal movement of the drive plate in opposite directions imparts pivotal movement of the front jaws radially inwardly and outwardly of the spindle axis.