Cast iron
Mild steel
Zinc
i think that it is quite difficult to cut mild steel because of its stiffness/strength
Equivalent material of mild steel ;is:206
Mild steel
mild steel.
mild steel .... and "Al"
Because hard steel would be brittle and break.
Per the attached related link, the density (hence weight) of stainless is slightly more than the mild carbon steel. Using about 8.03/7.84 ratio of density, for the same volume of material the stainless will weigh 2.4 % more.
Galvinised mild steel,
cheapest material is Mild steel having very good properties of shaft.
Cast iron, SS, Mild Steel