Abstract: On a chuck, the clamping jaws can be adjusted axially by means of an internally threaded sleeve of a jackscrew actuator in one direction for clamping and in the other direction for release. When the jaws are adjusted in the clamping direction, the clamping jaws are moved radially inward by interaction with a jaw convergence sleeve; for an axial movement in the release direction, the clamping jaws are moved radially outward by interaction with jaw expansion means attached inside the jaw convergence sleeve. The internally threaded sleeve is designed on its one end as an expansion cage for the clamping jaws lying inside the convergence sleeve, and is centered by an adjacent sleeve extension in the base unit. The internally threaded sleeve is guided both inside the expansion cage and inside the sleeve extension centering on the guide sleeve.