Abstract: A clamping shaft (12) for a rotationally driven part (14) is described. It comprises at least one fluid chamber (28a, 28b) being located inside a shaft body (16) and being delimited by a piston (30a, 30b) and a cylinder part (32a. 32b). Additionally, the fluid chamber (28a, 28b) is delimited by an elastic clamping region (24a, 24b) having a first diameter if the piston (30a, 30b) and the cylinder part (32a, 32b) are in a first relative position, and a second diameter if the piston (30a, 30b) and the cylinder part (32a, 32b) are in a second relative position. Furthermore, a preloading unit (38) is provided, biasing the piston (30a, 30b) and the cylinder part (32a, 32b) towards the second relative position. Moreover, a printing cylinder unit (10) of a printing machine is presented comprising such a clamping shaft (12). Also, a method for operating a clamping shaft (12) is explained.