Abstract: A machine tool is provided with a spindle clamping device for clamping a spindle assembly supported by a spindle head and composed of an outer spindle rotatably supported by the spindle head and an inner spindle disposed inside the outer spindle to be reciprocal along an axial direction thereof. The inner spindle is inserted into an inner hollow portion of the outer spindle so that a space is formed between an inner peripheral surface of the outer spindle and an outer peripheral surface of the inner spindle. The spindle clamping device comprises a pressure applying member such as a pair of pistons or oil ring disposed in the space between the outer and inner spindles for applying a pressure in an axial direction of the outer and inner spindles. The pressure applying member is provided with an oil chamber, and a pair of clamp rings are disposed in the space axially outside the pressure applying member.

Abstract: A device for clamping coaxial, first and second spindles of a machine tool to each other. The first spindle is hollow and rotatably supported by a spindle head. The second spindle is rotatably supported in the first spindle and can be moved back and forth in the axial direction of the second spindle. The device includes a space formed between portions of both the spindles; disc springs are provided in the space to exert an axial force; and a pair of clamp rings are disposed on both sides of the springs, for clamping both the spindles to each other due to a wedge action through the force of the disc springs. An oil chamber is formed at one side of the pair of clamp rings in order to release the clamping of both the spindles when oil pressure is applied. A hydraulic pressure source is provided for supplying pressurized oil into the oil chamber through a static pressure pocket provided at the place where the first spindle is in sliding contact with a bush encircling the first spindle.

Abstract: In a spindle of a machine tool, a cylindrical member of the spindle adapted to accommodate the shank of a tool is prepared by winding carbon or glass fiber and the wound fiber is impregnated with a heat curable resin. After curing the resin a protective coating layer is applied to the other surface of the cylindrical member.