A chuck-claw coupling mechanism includes a coupling member provided in a master jaw, a first resilient member, and an operation unit. The coupling member is movable between a coupling position at which the coupling member is coupled to the claw, and a separation position at which the coupling member is separated from the claw. The first resilient member urges the coupling member toward the coupling position. The operation unit moves the coupling member to the separation position.

A chuck-claw coupling mechanism includes a coupling member provided in a master jaw, a first resilient member, and an operation unit. The coupling member is movable between a coupling position at which the coupling member is coupled to the claw, and a separation position at which the coupling member is separated from the claw. The first resilient member urges the coupling member toward the coupling position. The operation unit moves the coupling member to the separation position.

A chuck includes a plurality of master jaws 20 that slide in the radial direction in the front surface of a body 10 in conjunction with slide of a plunger 40. The body 10 has a housing chamber 11 communicating with a plurality of keyways 13. The plunger 40 is fitted in the housing chamber 11. Each of the master jaws 20 includes a narrower part 21 and a wider part 22 fitted into an associated one of the keyways 13, and a wedge 23 connected to the plunger 40. The wider part 22 has a flat wider sliding surface 22b radially outside the wedge 23. Each of the keyways 13 has a wider slid surface 14.

A chuck includes a plurality of master jaws 20 that slide in the radial direction in the front surface of a body 10 in conjunction with slide of a plunger 40. The body 10 has a housing chamber 11 communicating with a plurality of keyways 13. The plunger 40 is fitted in the housing chamber 11. Each of the master jaws 20 includes a narrower part 21 and a wider part 22 fitted into an associated one of the keyways 13, and a wedge 23 connected to the plunger 40. The wider part 22 has a flat wider sliding surface 22b radially outside the wedge 23. Each of the keyways 13 has a wider slid surface 14.

A chuck mechanism of the present invention includes multiple master jaws placed movably in a radial direction on a front surface of a chuck body, and top jaws each detachably attached to front surfaces of the top jaws. Each master jaw and each top jaw have a raised portion and a recessed portion engageable with each other. Each of the raised and recessed portions has conical surfaces formed by part of a conical body. Each top jaw has a gripping surface formed by part of a circular columnar body. Upon work gripping, the center axes of the conical surfaces on a gripping side among the conical surfaces of each master jaw and each top jaw and the center axis of the gripping surface are all coincident with a rotation axis of the chuck body.

A chuck mechanism of the present invention includes multiple master jaws placed movably in a radial direction on a front surface of a chuck body, and top jaws each detachably attached to front surfaces of the top jaws. Each master jaw and each top jaw have a raised portion and a recessed portion engageable with each other. Each of the raised and recessed portions has conical surfaces formed by part of a conical body. Each top jaw has a gripping surface formed by part of a circular columnar body. Upon work gripping, the center axes of the conical surfaces on a gripping side among the conical surfaces of each master jaw and each top jaw and the center axis of the gripping surface are all coincident with a rotation axis of the chuck body.