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 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 chuck with automatic positioning collet is provided. The chuck includes a rotation member, over which a stationary member is sleeved. A piston is arranged inside the rotation member by means of a slidable sleeve that includes an internal thread screwed to an external thread of a collet. The rotation member includes an elastic piston pin assembly selectively alignable with a positioning groove of the collet. The stationary member is provided with two gas passages through which gas introduced may drive the piston to move in opposite directions so as to move the slidable sleeve and the collet in opposite directions to cause a tapering hole of the rotation member to loop tightly up or release the collet and an object received in the collet and the gas simultaneously drives the elastic piston pin assembly to position the positioning groove of the collet.

A chuck with automatic positioning collet is provided. The chuck includes a rotation member, over which a stationary member is sleeved. A piston is arranged inside the rotation member by means of a slidable sleeve that includes an internal thread screwed to an external thread of a collet. The rotation member includes an elastic piston pin assembly selectively alignable with a positioning groove of the collet. The stationary member is provided with two gas passages through which gas introduced may drive the piston to move in opposite directions so as to move the slidable sleeve and the collet in opposite directions to cause a tapering hole of the rotation member to loop tightly up or release the collet and an object received in the collet and the gas simultaneously drives the elastic piston pin assembly to position the positioning groove of the collet.