Abstract: A printing cylinder for printing machines comprising a shaft, a sleeve adapted to support a printing block and mounted on the shaft with radial clearance, and an adjusting mechanism provided at each end of the sleeve. Each adjusting mechanism comprises a guide ring and a clamping ring having cooperating conical guide surfaces. A fit between the shaft and the guide ring is so easy that the guide ring may be somewhat tilted relative to a plane at right angles to the longitudinal axis of the shaft, and the clamping ring comprises radial, adjustable securing means and axial adjusting means, whereby it is possible to center the sleeve very precisely relative to the shaft.