Abstract: The invention is a pressure rig for repetitive casting of metal. The pressure rig performs like a piston for feeding molten metal into a mold. Pressure is applied to an expandable rubber diaphragm 22 which expands like a balloon to force the metal into the mold. A ceramic cavity 26 which holds molten metal is lined with blanket-type insulating material 11, 15, necessitating only a relining for subsequent use and eliminating the lengthy cavity preparation inherent in previous rigs. In addition, the expandable rubber diaphragm 22 is protected by the insulating material 14 thereby decreasing its vulnerability to heat damage. As a result of the improved design the like expectancy of the pressure rig contemplated by the present invention if more than doubled. Moreover, the improved heat protection has allowed the casting of brass and other alloys with higher melting temperatures than possible in conventional pressure rigs.