Abstract: The invention relates to a winding shaft for winding a continuous flexible material web into a roll. The winding shaft has means in order to adjust the diameter of the winding shaft surface to be wound between a reduced-diameter unused position and an expanded operating position, and the winding surface in the expanded position is formed jointlessly with a uniform curvature and is supported inward against the operational pressure around said winding surface in a dimensionally stable manner that is substantially uniform. A roll can thereby be wound without disruptions and then stored without a casing until the roll “dies”, said roll remaining stable during storage and not forming any disrupted zones on the inner face of the roll.