Tool Steel - O1 Tool Steel is a type of carbon alloy steel that is suitable for tool manufacturing, such as hand tools or machine dies. Its hardness, resistance to abrasion and ability to retain shape at increased temperatures are key properties of this material. Tool Steel is typically used in a heat-treated condition which provides increased hardness. O1 is a general-purpose oil hardening tool steel. It has good abrasion resistance and toughness for a wide range of applications. Typical applications of O1 Tool Steel include Arbors, Bushing, Chasers (Thread Cutting), Collets, Die Blanking, Cold Forming, Cold Trimming, Drill Bushing, Gages, Knurling Tools.