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 perforating apparatus for a cylindrical workpiece, including: a cradle having a groove extending in one direction horizontally from one end to another end; a stopper provided at the one end of the groove; a drill disposed vertically above the groove and movable at least in vertical direction, having a drill bit that extends vertically; and a chuck having a pair of opposing grippers movable toward each other in a horizontal direction perpendicular to the direction in which the groove extends, and symmetrically with respect to a rotation axis of the drill bit, each of the grippers further having a pair of vertically symmetric inclined surfaces expanding upwards and downwards.

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.

Provided is a method for manufacturing a gripping tool for gripping a workpiece with top jaws (30) attached to a plurality of master jaws (20) attached to a gripping tool body (10). A first positioner (21, 24) that determines the distance of the top jaw from the center axis of the top jaw when the top jaw is attached to the master jaw is formed in a direction perpendicular to a slide direction in a surface of the master jaw. The method includes a step of attaching the plurality of master jaws to the gripping tool body, a step of gripping a shaping plug (70) by sliding the plurality of master jaws toward the center axis, and a step of finishing, in the surface of the master jaw, the first positioner extending in the direction perpendicular to the slide direction.

A chuck (10) includes a jaw guide (64), interleaving jaws (66), and an inclined engagement surface (84). The jaw guide defines a longitudinal axis (24) and includes jaw channels (65) circumferentially distributed about the axis. The jaws are slidably disposed in the jaw channels Each jaw has a clamping surface (88) facing the axis and a driving surface (90) substantially opposite the clamping surface and a protrusion (92) on a first lateral side and a cavity (96) on a second lateral side. The protrusion of each jaw is disposed at least in part in the cavity of an adjacent jaw. The engagement surface is on one of an inner surface of the jaw guide and an engagement sleeve (80), and is substantially centered about the axis and substantially parallel to the driving surface. Displacement of the jaws relative to the engagement surface in a clamping direction displaces the clamping surfaces toward the axis.

A chuck for clamping a shaft. The chuck includes a jaw guide defining an axis and including jaw channels circumferentially distributed about the axis. Interleaving jaws are slidably disposed in the jaw channels and each jaw has a clamping surface facing the axis and a driving surface opposite the clamping surface and a protrusion on one side and a cavity on another side with the protrusion of each jaw disposed at least partially in the cavity of an adjacent jaw. A spring having a base and fingers extending from the base are engageable with the jaws to retain the jaws in the jaw channels. An inclined engagement surface is included on an inner surface of the jaw guide or an engagement sleeve. Displacement of the jaws relative to the inclined engagement surface in a clamping direction displaces the clamping surfaces toward the axis.