HSS M2, M35 and M42: what the grades mean

M2, M35 and M42 are three grades of high speed steel (HSS). M2 is the general-purpose grade with no cobalt. M35 is M2-type steel with about 5% cobalt, and M42 carries about 8% cobalt. Cobalt raises heat resistance, which is why the cobalt grades are used on harder or hotter cutting work.

Nominal composition

Composition is in percent by weight and is nominal. Sources list the grades with small differences, so treat the figures as typical, not exact. The hardness a tool reaches depends on its heat treatment.

What cobalt changes

Cobalt increases heat resistance. Tool makers call this red-hardness: the ability to keep the cutting edge hard when it gets hot. M35 has some of the red-hardness of M42 and is less susceptible to shock, while M42 has very good red-hardness for working difficult materials.

Where each grade is used

• M2: general work and production machining.
• M35: sits between the two. It is also sold as HSS-E or HSS-Co, labels used for cobalt-bearing steels.
• M42: the cobalt grade chosen for difficult materials.

Grades in the BVF range

We state a grade only where the product page states it.

• IT Brand HSS M2 Hathyar 600 Tool Bit: the page states Material HSS M2.
• IT Brand Hand/Machine HSS Tap Set M6 x 1.0: the page describes the material as 6542 high-speed steel (M2).
• Gemco HSS Tool Bits 3/8" x 8", Totem M6x1.0 HSS Tap Set and HSS Jobber Drill 3.00mm - 3.90mm: the pages say HSS and do not state a grade, so we do not give one.

What to check

• Read the grade on the product page, not only the word HSS.
• Match the grade to the work: cobalt grades for harder or hotter cutting, M2 for general work.
• A harder grade is not a tougher one: M35 handles shock better than M42.

Related collections

• HSS Tool Bits
• Taps & Tap Sets
• HSS Drills