A main spindle device includes: a main spindle; a rod accommodated in the main spindle, the rod being capable of moving to an unclamp position in a direction toward the first end, and when the main spindle is holding a tool, being capable of moving to a clamp position in a direction toward a second end; a biasing unit that biases the rod in the direction toward the second end with respect to the main spindle and that biases the rod to the clamp position when a collet is holding the tool; and a biasing force detector that detects a biasing force of the biasing unit which biases the rod in the direction toward the second end after the rod is moved in the direction toward the first end with respect to the main spindle to the unclamp position by force larger than the biasing force of the biasing unit.

A hydraulic chuck device includes a cylinder portion operated by pressure oil, a chuck opened and closed by operation of the cylinder portion, a pressure oil supply controlling pressure of pressure oil supplied to the cylinder portion, and a chuck controller controlling the pressure oil supply. When controlling the pressure oil supply to cause a jaw portion to perform a clamping operation, during movement of the jaw portion from an unclamping position to a preliminary position situated before a clamping position, the chuck controller supplies pressure oil set at a first pressure into a cylinder chamber for clamping to move the jaw portion quickly, and during movement of the jaw portion from the preliminary position to the clamping positon, the chuck controller supplies pressure oil set at a second pressure lower than the first pressure into the cylinder chamber for clamping to move the jaw portion slowly.

A method for determining the clamping force of a force-actuated, rotationally drivable clamping device of a machine tool. An object is clamped with an actuation force F. Model-based calculation of the clamping force F.sub.calc to be expected is performed based on the actuation force F and the operating parameters of the machine tool in a control unit of the machine tool. Performing clocked measurement of the clamping force F.sub.real acting upon the object in the clamping device within the time span of a measurement interval I. Wireless transming the measured value F.sub.real to the control unit of the machine tool, and comparison of the measured value F.sub.real with the calculated clamping force F.sub.calc. The measurement interval is adapted if the comparison reveals a deviation which reaches a threshold value.

A workpiece holding device for holding a workpiece in a heat treatment system while the workpiece undergoes a thermal expansion and/or contraction includes at least two clamping units configured to apply a radial and/or an axial clamping force to the workpiece to hold the workpiece in the workpiece holding device in a predefined position, and at least three support units configured to support the workpiece. A first one of the at least three support units includes a first cylinder configured to support the workpiece, the first cylinder having a longitudinal axis and being configured to rotate around the longitudinal axis.

A workpiece holding device for holding a workpiece in a heat treatment system while the workpiece undergoes a thermal expansion and/or contraction includes at least two clamping units configured to apply a radial and/or an axial clamping force to the workpiece to hold the workpiece in the workpiece holding device in a predefined position and a drive unit configured to rotate the workpiece in the workpiece holding device. The at least two clamping units may be configured to adjust their position relative to the holding device to maintain the clamping force during the thermal expansion and/or contraction of the workpiece.

A workpiece holding device for holding a workpiece in a heat treatment system while the workpiece undergoes a thermal expansion and/or contraction includes at least two clamping units configured to apply a radial and/or an axial clamping force to the workpiece to hold the workpiece in the workpiece holding device in a predefined position, and at least three support units configured to support the workpiece. At least one of the support units includes a carrier and an exchangeable support element attached to the carrier, the exchangeable support element being configured to contact and rotatably support the workpiece in the predefined position.

A method of manufacturing a modular clamping device for clamping a rotationally symmetrical body on a spindle head of a motor spindle is disclosed. The modular clamping device includes a clamping element and a first intermediate piece. In the method, a first intermediate piece assembly (22) is provided having a plurality of prefabricated, standardized first standard intermediate pieces. The first intermediate piece (210) is selected from the first intermediate piece assortment (22). The clamping element is fabricated, and the first intermediate piece is positioned relative to the clamping element such that the first intermediate piece is positioned axially between the spindle head and the clamping element when the clamping device is mounted to the spindle head.

A wheel fixture is disclosed. A main shaft drives a first positioning pull rod on a chuck body to extend and contract in the radial direction via a tightening screw, a clamping jaw is at a position within the travel range of extension and contraction, a wheel is positioned and clamped by the fixture, airtight support blocks are pressed down by the wheel and flush with the support plane of the clamping jaw, at this time, airtight ejector rods press second O rings to prevent air from flowing out of the airtight detection position, a detection system of a machine tool detects a preset air pressure value which indicate that the wheel has been placed correctly, and if the wheel is not placed correctly on the fixture, the machine tool will alarm through the detected pressure feedback.

A machine tool includes: a hollow spindle including a hollow portion along an axial direction; a plurality of chuck claws openably mounted at a distal end portion of the hollow spindle, and configured to hold a workpiece; an operation rod inserted into the hollow portion of the hollow spindle in a movable manner, and configured to close the plurality of chuck claws with movement of the operation rod toward one side in the axial direction and open the plurality of chuck claws with movement of the operation rod toward the other side in the axial direction; and a measuring apparatus configured to measure an opening dimension of the plurality of chuck claws based on a movement amount of the operation rod.

A workpiece holding device includes: a chuck including a chuck body, and a plurality of chuck claws openably supported on the chuck body and configured to hold a workpiece; an operation rod configured to drive the plurality of chuck claws for opening and closing with movement of the operation rod; and a measuring apparatus configured to measure an opening dimension of the plurality of chuck claws based on a movement amount of the operation rod.