Abstract: A machine for use in forming ductile metal sheets into shaped bodies having first and second open-ended, annular chambers which are relatively movable, while maintaining their open ends in register with one another, between a position in which the open ends meet and a position in which the open ends are spaced apart, a plate in at least one of the chambers which is movable independently of both chambers in directions parallel with the directions of relative movement between the chambers between a first position in which it constitutes a gas tight sealed base for said one chamber and a second position in which it is adjacent the open end of that chamber.