Why is it so difficult to cut through cast iron?
Cast iron in it pure state is called grey cast or pig iron and in bygon times was used to tip cutting tool because it is one of the hardest metals they had .Normaly cast Iron is very easy to cut and drill as the carbon acts like wax,but if the iron as been chilled when made or quenched in water it reverts back to gray cast this also happens when casting thin pipes like drain pipes.