Hydraulic expanding chuck

A hydraulic expansion chuck comprising a base body, which extends along a rotational axis and which has a clamping part for receiving and clamping a shaft tool, and a shaft part comprising a hollow shaft for directly or indirectly coupling the hydraulic expansion chuck to a module of a modular tool system or to a machine spindle, wherein the clamping part has a central receiving opening and, around the receiving opening, at least one pressure chamber, to which fluid pressure can be applied and which is separated from the receiving opening via an elastically resilient expansion wall and which is connected via a pressure duct to a pressure generating means arranged in the base body,

• axially in the region between the receiving opening and the hollow shaft, the pressure generating means is arranged in a central recess, which is coaxial to the receiving opening and which leads into the hollow shaft, and can be actuated through the hollow shaft.