Abstract: A thin-walled hollow metal cylinder is rotatably held at its ends between holding flanges which are mounted with a pressure-tight seal on an opposing aligned pair of rotatable hubs. The spacing between the hubs can be adjusted. In one embodiment, the hubs are supported on a hollow pipe arbor and make a pressure-tight seal against it. In another embodiment, one hub is mounted on a stub shaft which is held in bearings and another is held in the head stock of a lathe in proper alignment. In both cases, a pressure medium, air, is supplied to the inner space of the cylinder through the arbor at a pressure of about 0.5 to about 1.0 atmospheres to increase the inherent rigidity of the cylinder. This improves the stability of the cylinder for various processes, such as for photoengraving of the surface of the cylinder to prepare it as a screen-printing stencil.