O1 Steel Hardness: Annealed, Quenched and Tempered HRC Range O1 tool steel is usually supplied in the annealed condition, with a hardness typically not exceeding about 217 HBW. After oil quenching, O1 can reach about 64–65 HRC in the as-quenched condition. For practical use, O1 steel is hardened and tempered. Its typical hardness is about 58–60 … Continue reading O1 Steel Hardness: Annealed, Quenched & Tempered HRC Guide