Chuck device and method for attaching child jaws

A method for attaching a sub jaw in a chuck device including

• a chuck main body configured to rotate about an axis of a spindle,
• a locator configured to be detachably attached to the chuck main body,
• a master jaw configured to be attached to the chuck main body, and
• a sub jaw configured to be detachably attached to the master jaw and to clamp a workpiece brought into contact with the locator from an outside in a direction orthogonal to the axis, in which
• the master jaw includes,
• a recessed portion recessed in a direction parallel to the axis, and
• a locking portion provided outside the recessed portion in a direction orthogonal to the axis, and
• the sub jaw includes,
• a biasing member having an elastic member and an insertion member to which an elastic force of the elastic member is applied,
• a plate, and
• a locked portion,
• the method comprising:
• a step of disposing the master jaw between the plate and the biasing member in a direction parallel to the axis;
• and
• a step of sliding the sub jaw outward in a direction orthogonal to the axis with respect to the master jaw in a state in which the master jaw is disposed between the plate and the biasing member, inserting the insertion member into the recessed portion from a direction parallel to the axis by an elastic force of the elastic member, clamping the master jaw between the insertion member inserted into the recessed portion and the plate, and bringing the locked portion into contact with the locking portion from an inside in a direction orthogonal to the axis to lock the locked portion.