PURPOSE: To permit the captioned chuck to be adapted for a full automatic unmanned machine by allowing all catching hooks and engagement members to be simultaneously engaged and released by retreating the engagement member in the axial direction by an engaging and releasing mechanism, correlated to the operation of the catching and releasing member of a chuck.

CONSTITUTION: An engaging and releasing mechanism 25 consists of a draw plate 26, draw arm 27, and a set pin 29. In the inoperative position of the engaging and releasing mechanism 25, an engagement member 18 is locked by the set pin 29, and a set bar 28 is locked by a set ball 35, so the whole mechanism is formed into an integrated rigid body, and protrusion of the whole body outside a chuck body can be prevented. Further, even in any operation such as high-speed revolution and/or high load cutting, generation of such a trouble that the engagement between the engagement member 18 and a catching hook 39 is released can be prevented.