Originally Posted by
chevynut
Yes I agree that if you take a patch piece from a car from the 50's it's going to be different composition than metal taken from a car built today. Today's cars are made with thinner, stronger steel. I wouldn't think of using metal from a modern car for a simple patch panel.
However, that doesn't mean you can't get metal of the same composition that they used in the 50's, which was probably a mild (low carbon) steel. Plain mild steel sheet you can get today is usually something like 1008 to 1020 steel (.08% to .20% carbon) and it's likely similar to what they used back then. I'm not sure but I doubt the thermal expansion of mild steels differs much.