Abstract: An upper die is movable by a ram downwardly against a lower die with the dies enclosing a hollow article such as a knobshell in die cavities thereof. RAM continued downward movement of the closed dies forces a piston connected to the lower die downwardly against hydraulic fluid of a containing cylinder forcing the hydraulic fluid internally of the knobshell through the neck thereof forming the knobshell outwardly against the die cavity surfaces. The piston size compared to the knobshell size automatically creates a reactive force reversely tending to maintain the dies closed greater than the internal knobshell forming force tending to separate the dies. After knobshell forming, reverse ram movement first relieves piston pressure against the hydraulic fluid and ultimately separates the dies with a knockout member being actuated to eject the formed knobshell.