In a process for casting a plate grid for a lead-acid storage battery comprising the steps of preparing a casting die assembly including two interengagable die halves between which is formed a casting cavity to cast a plate grid therein and pouring a molten metal of lead or lead alloy into said casting cavity to form said plate grid therein, an air in said casting cavity is vented through gaps between said die halves and then through a narrow air passage in at least one venting member received in either of said die halves so that said venting member is flush with the casting surface of the corresponding die half, said venting member at the top surface having cavity forming portions operatively associated with said die halves.