High precision chuck with centering function

A vertical lathe comprising:

• a spindle;
• a chuck attached to said spindle and rotatable together with said spindle;
• a tool post configured to hold a tool;
• a moving device configured to move said tool post:
• and
• a control device configured to control said moving device, so as to control movement of the tool held by said tool post relative to an object chucked by said chuck during machining performed by said vertical lathe,
• wherein said chuck includes:
• (i) a main body having a central axis:
• (ii) three jaws each movably held med to said main body;
• (iii) a jaw driving device configured to cause each of said three jaws to be radially moved relative to said main body in synchronization with one another, said jaw driving device including (iii-1) a driving member which is slidably fitted with a central guide provided in a central portion of said main body, and which is movable in opposite directions parallel to an axial direction parallel to said central axis, and (iii-2) a movement converting mechanism provided between said driving member and said three jaws, and configured to convert axial movement of said driving member into radial movement of each of said three jaws,
• (iv) a biasing device biasing said driving member relative to said main body in a forward direction that is one of said opposite directions;
• and
• (v) a force receiving portion configured to receive, from a front side of a front surface of said main body, a backward force forcing said driving member to be moved, against a biasing force generated by said biasing device, in a backward direction that is the other of said opposite directions, and
• wherein said control device is configured to control said moving device so as to move said tool post relative to said chuck, such that said tool post applies the backward force to said force receiving portion of said chuck, thereby moving said driving member in the backward direction and causing said three jaws to be radially moved relative to said main body.