Cleveland M42 cobalt heavy duty jobber length drill bit set. Cobalt steel tools are similar to high-speed steel, but with more cobalt for improved performance when cutting harder metals such as stainless steel or nickel alloys. Gold oxide is a thinner oxide surface treatment than black oxide typically used to identify cobalt steel tools; performance is similar to uncoated tools. High red hardness for extended wear life in high heat conditions. Applicable for aluminum, copper alloys, inconel, titanium alloys, tool steel, die steel, structural steel and precip-hard stainless.