Chuck mechanism

A chuck mechanism comprising:

• a chuck main body;
• a plurality of master jaws installed on a front surface of the chuck main body so as to be movable in a radial direction;
• and
• top jaws each removably attached to a front surface of each of the master jaws,
• wherein, at portions facing to each other in an axial direction, each of the master jaws and each of the top jaws respectively comprise a side surface shaped to be conical and are respectively provided with a projecting part and a recessed part which engage with each other;
• a movable pin movable in the axial direction and a shaft movable in the radial direction are disposed in each of the master jaws;
• the movable pin is engaged with the shaft so as to be movable in the axial direction by rotating the shaft;
• each of the top jaws is provided with a pin hole into which the movable pin can be inserted;
• the chuck mechanism further comprises a lock mechanism by which the movable pin is locked at a first position in which the movable pin is inserted into the pin hole or at a second position in which the movable pin is extracted from the pin hole respectively by rotating the shaft by a predetermined amount;
• the lock mechanism comprising a shaft cover provided in each of the master jaws so as to surround an outer periphery of the shaft;
• and a lock pin protruding outward on the outer periphery of the shaft;
• a first groove and a second groove are formed with a fixed distance therebetween on an outer periphery of the shaft cover along a circumferential direction so as not to be on a same circumference;
• and
• the lock pin is configured to be engaged with the first groove or the second groove by rotating the shaft by the predetermined amount to lock the movable pin at the first position or the second position.