Chuck, particularly for machine tools

Chuck, particularly for machine tools, for centering and locking a workpiece to be machined, comprising a structure supporting a table provided with first sliding seats extending radially from the center of said table and accommodating workpiece centering means controllably movable towards and away from the center of the table and intended to contact portions of the workpiece arranged above said table and with second sliding seats extending radially from the center of said table and accommodating workpiece locking means controllably movable towards or away from the center of the table from a first position spaced from the portions of the workpiece to be contacted to a second position proximate to said portions of the workpiece to be contacted and controllably movable in a direction substantially perpendicular to the face of the table directed towards the workpiece from a release position, in which said locking means are disengaged from the workpiece, to an engagement position in which said locking means are engaged with the workpiece, said chuck further comprising control means acting on said centering means for their movement towards or away from the center of the table and on said locking means for their passage from said first to said second position and vice versa, there being provided means for connecting said control means to said locking means in said second position for the passage of said locking means from said release position to said engagement position or vice versa.