PURPOSE: To prevent the burr generation of a mold by arranging a vent stock having an elasticity on the back face of the porous metal on the side face of which an engraving is executed and forming a mold by fitting it to a substrate.

CONSTITUTION: A grating body for a lead battery is engraved on one face of the vent porous metal 3 of a cast iron, etc., and on its back face the elastic body 2 of a polytetrafluoroethylene plate, etc., having elasticity and permeability is stuck. A mold is formed by the metal plate which becomes a substrate 1 as well. The elastic body 2 is completely fitted to a vent porous metal 3 due to the elasticity of the material and in case of casting a molten lead alloy the invasion of the molten metal into the gap between the elastic body 2 and porous metal body 3 is prevented. The burr generation on the mold is surely prevented even if the pouring cycle of the molten lead alloy is repeated may times continuously.