A hollow workpiece having a tubular end portion is deformed by first fitting the workpiece into a die formed with a cavity adapted to receive the workpiece with the end portion of the workpiece projecting along an axis out of the die and then engaging over the projecting end portion of the workpiece a feed sleeve in a pressure-tight fit. The sleeve and workpiece are supported relative to each other such that the holding portion can slide in the sleeve and that the sleeve exerts substantially no axial force on the workpiece. Then an interior of the workpiece is pressurized through the sleeve and to deform the workpiece outward against an inner surface of the die.