What is the difference between M35, M42 and M48 cobalt?

High-speed steel (HSS) Cobalt is a type of steel alloy that contains cobalt as an alloying element, enhancing the steel's hardness, heat resistance, and wear resistance.

M35 Cobalt (UNS T11335): 

M35 is a high-speed steel with 5% cobalt content, providing excellent wear resistance, red hardness, and toughness. It is commonly used for cutting tools and drill bits.

M42 Cobalt (UNS T11342):

M42 is another high-speed steel with 8% cobalt content, offering superior heat resistance and hardness. It is often used for high-speed cutting tools and for machining tough and abrasive materials.

M35 Cobalt Drill Bit (bottom left) vs M42 Cobalt Drill Bit (top right) - note the slightly darker colour in the M42 bit due to higher cobalt content.

M48 Cobalt (UNS T11348):

M48 is a high-speed steel with even higher cobalt content, typically around 10%. It offers excellent wear resistance and is suitable for demanding cutting applications.

These are some of the popular grades of HSS cobalt, but there are other variations and proprietary grades developed by different manufacturers. It's important to check with the specific supplier or manufacturer for the most up-to-date and precise information on HSS cobalt grades.

See our full range of cobalt drill bits here