Structure and chuck

A chuck configured to grasp a work at front of a body, comprising:

• a guide groove provided along a radial direction at a front side of the body;
• a master jaw configured to open/close in the radial direction along the guide groove, the master jaw having a first space, and being movable in such a manner that translational movement of a plunger in direction of a rotation axis can be converted into translational movement of the master jaw in the radial direction;
• a top jaw having a second space,
• a T-nut configured to be accommodated in the first space;
• a bolt configured to be accommodated in the second space, wherein the first space is a T-groove having an inverted T-shape and accommodating the T-nut, the second space is a through hole allowing the bolt to penetrate, a bolt hole is provided on the T-nut, and the bolt is configured to be screwed into the bolt hole,
• the top jaw being configured to be attached to/detached from the master jaw by loosening the bolt;
• a grasping portion provided on at least one of the T-nut and the bolt, and configured to allow the top jaw, the T-nut and the bolt to be integrally moved radially outward and detached from the T-groove by grasping the grasping portion in a state where the bolt is loosened;
• and
• wherein:
• the top jaw further comprises a locking member, and
• when the bolt is loosened, one end of the bolt presses the top jaw through the locking member, thereby the top jaw is configured to be forcibly separated from the master jaw.