This is just a curiority question since I don't think it is a mechanical issue. Does anyone know why or what the purpose is for the lead "rivit" that is in the hole opposite the inspection hole on the Z car brake drums? Mine is a '72 and I just had the drums turned and one of the lead fittings broke. I plan on just putting a rubber filler plug in there (same as the inspection hole) but what is the purpose of the lead fitting? Harry