The invention relates to a chuck with chuck jaws (2) which are guided in the chuck housing (1). Inner jaws (4) which can be coupled or uncoupled are assigned directly or indirectly to said chuck jaws via rack gears (3), whereby the inner jaws (4) are connected to a central pulling head (12) via a wedging mechanism. The pulling head is connected via a rod or hollow shaft (13), said rod or hollow shaft being guided in a central bore of the main spindle (25), to the piston of a hydraulic cylinder arranged on the rear part of the main spindle (25).