Fixture and clamping housing

A fixture to hold a workpiece (2) to be machined on a tool table of a machine tool, the fixture comprising:

• a clamping housing (10) having a passage opening (11) into which a clamping pin (12) is inserted for supporting the workpiece (2) on the clamping housing (10);
• a driving ring (15) mounted in the clamping housing (10) in such a way as to be able to rotate, which is in a driving active connection with a driving spindle (20) inserted in the clamping housing (10), by means of which the driving ring (15) can be adjusted about a longitudinal axis (11′) of the passage opening (11) within a specified angle range (α);
• and
• at least two locking pins (18) facing the longitudinal axis (11′) of the passage opening (11), mounted radially in the clamping housing (10) so as to be able to move, and each of which is connected to the driving ring (15) in a driving arrangement, by means of which the clamping pin (12) is locked in the passage opening (11) of the clamping housing (10) when the at least two locking pins (18) are moved radially inboard toward the longitudinal axis (11′), and released from the passage opening (11) of the clamping housing (10) when the at least two locking pins (18) are moved radially outboard away from the longitudinal axis (11′);
• characterised in that,
• a control surface (21) or control cam with at least two different pitches (22, 23) is worked onto an inside (16) of the driving ring (15) in each area of the at least two locking pins (18), that an accommodating pocket (19) with a U-shaped cross section is worked into corresponding locking pins of the at least two locking pins (18) into which the driving ring (15) is inserted, and that a contact surface (25) is worked onto or provided on a wall of the corresponding locking pins of the at least two locking pins (18) facing an inner wall (16) of the driving ring (15) and the contact surface (25) is in contact with the control surface (21) or control cam of the driving ring (15) and is configured to move the corresponding locking pins of the at least two locking pins (18) radially inwards or outwards depending on a direction of rotation of the driving ring (15).