Abstract: Polyvalent clamp chuck for machine-tools comprising a cylindrical chuck body in the front face of which are radially guided at least two gripping jaws that can be brought together or separated by drive means by the axial withdrawal or advance of an internal control cylinder concentric with the chuck. The control cylinder is provided at its front end with a connector member, for instance in the form of an inwardly directed gripping flange for additional fitted support means. The coaxial front opening of the chuck has a conical part whose summit is oriented rearwards. The chuck further comprises means for selecting the maximum amplitude of displacement of the control cylinder.