Tool steelsUNS T11302

M2 High-Speed Tool Steel

Also: AISI M2, UNS T11302, W.Nr. 1.3343, DIN 1.3343, HS6-5-2, HS6-5-2C, SKH51 (JIS), Böhler S600, M2 HSS, high-speed steel, HSS, M-2

M2 is the general-purpose high-speed steel: 60-65 HRC with red hardness, for drills, taps, end mills, broaches and wear-resistant punches.

ASTM A600 (high-speed tool steels)ISO 4957 / EN ISO 4957 (HS6-5-2C)

Sourcing M2 parts or stock?

Attach a drawing (PDF or STEP) or describe the part; a U.S. shop that fits quotes it.

At a glance

M2 High-Speed Tool Steel typical properties
Density	8.16 g/cm³ (0.295 lb/in³)
Tensile strength	About 760-880 MPa (110-128 ksi) annealed, estimated from hardness. Not a published property at 60-65 HRC, where M2 is rated by hardness, red hardness and compressive strength.
Yield strength	n/a: tensile yield is not commonly published for hardened M2, which fractures with almost no plastic strain in tension.
Hardness	About 220-255 HB annealed; 60-65 HRC working hardness (62-65 HRC typical for cutting tools)
Elongation	Not meaningful at working hardness (near zero in tension); tools are designed around hardness and edge toughness
Modulus of elasticity	215 GPa (31 Msi)
Thermal	Hardened from 1,175-1,230 °C (2,150-2,250 °F), close to its incipient melting point; red hardness: resists softening in service up to roughly its 540-595 °C (1,000-1,100 °F) tempering temperature
Composition	Fe, 0.78-0.88% C (0.95-1.05% in high-carbon M2), 5.50-6.75% W, 4.50-5.50% Mo, 3.75-4.50% Cr, 1.75-2.20% V

Typical values, Hardened from about 1,175-1,220 °C (2,150-2,225 °F) and triple tempered at 540-565 °C (1,000-1,050 °F) to 60-65 HRC. Annealed stock is about 220-255 HB.. Confirm against the mill certificate and the purchase spec.

MachinabilityFair: About 50% of the W1 (1% carbon tool steel) benchmark annealed: abrasive and slow. Rough machine annealed, harden, then grind; hardened M2 is ground or wire-cut, not machined.
WeldabilityPoor: Not a welding grade. Broken HSS tools are rarely worth repairing; if attempted, preheat to roughly 500-550 °C (930-1,020 °F) and temper after. Drills and reamers are often made by friction welding an HSS body to a carbon steel shank, a controlled production process.
FormabilityPoor: Machined and ground from bar, flat and blanks; not formed.
Corrosion resistancePoor: Rusts; tools are protected with steam oxide, black oxide, PVD coatings or oil.

M2 is a molybdenum-tungsten high-speed steel with about 0.85% carbon, 6% tungsten, 5% molybdenum, 4% chromium and 2% vanadium. Hardened from a very high temperature and tempered three times, it reaches 60-65 HRC through secondary hardening, and it keeps that hardness when the cutting edge runs hot. That property, red hardness, is what lets high-speed steel tools cut at speeds that would soften carbon or cold work tool steel. M2 is the most widely used high-speed steel.

Carbide has taken over most production turning and milling, but M2 still owns drills, taps, reamers, broaches, form tools, saw blades and cutters for interrupted cuts and less rigid machines, where its toughness and low cost matter more than speed. It is also a cold work die steel: punches and dies for thin, hard or abrasive stock use its high compressive strength and wear resistance.

Heat treatment is a specialist job. The hardening temperature sits close to the point where the steel starts to melt at its grain boundaries, the soak is short, and at least three tempers are needed. Annealed M2 machines slowly, and hardened M2 is ground. For more hot hardness, the cobalt grades (M35, M42) are the next step; for more wear resistance and toughness, powder-metal high-speed steels.

Heat treatment

Preheat in two or three steps (for example about 540-650 °C (1,000-1,200 °F), then 815-870 °C (1,500-1,600 °F)), austenitize at 1,175-1,230 °C (2,150-2,250 °F) for only a few minutes, and quench in salt, oil or high-pressure gas. Temper at least three times at 540-565 °C (1,000-1,050 °F), cooling to room temperature between tempers, to transform retained austenite and develop secondary hardening. Lower hardening temperatures give tougher punches and cold work tools; higher ones give the most red hardness for cutting tools. Anneal at 870-900 °C (1,600-1,650 °F) with a slow cool, and always anneal before re-hardening.

Tempers and conditions

Annealed (about 220-255 HB), as stocked
Hardened and triple tempered, 62-65 HRC (cutting tools)
Hardened and tempered, 60-62 HRC (punches and cold work tools)
Hardened and ground tool bits and blanks

Stock forms

Round bar and drill rod
Flat bar
Square and rectangular tool bits (hardened and ground)
Tool blanks, discs and rings
Powder-metal (PM) M2 bar

Relative cost

Tier 4 of 5. Roughly 2-3x D2 per pound because of the tungsten, molybdenum and vanadium; cobalt (M35, M42) and powder-metal grades cost more again. Heat treatment and grinding often cost more than the steel.

Typical applications

Twist drills, taps and reamers
End mills, form cutters and gear cutters
Broaches
Lathe tool bits and form tools
Circular saw and hacksaw blades
Punches and dies for thin, hard or abrasive stock
Cold heading and cold forming punches

Process compatibility

How M2 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

M2 High-Speed Tool Steel process compatibility
Process	Rating	Notes
CNC Grinding	ExcellentExcellent	The main process for M2: tools and punches are ground to finish after hardening. Use aluminum oxide or CBN wheels with flood coolant; grinding burn softens and cracks the edge.
Centerless Grinding	GoodGood	Drill blanks, pins, punches and drill rod are centerless ground.
CNC Machining	FairFair	Annealed only, and slow; rough machine, harden, then grind.
Wire EDM	GoodGood	Cuts hardened punches and form tools; remove the recast layer from cutting edges.
Sinker EDM	GoodGood	Forms cavities and shapes in hardened punches and dies; skim off the white layer.
Vacuum Heat Treating	ExcellentExcellent	Vacuum furnaces with a high-pressure gas quench handle the 1,200 °C cycle cleanly with no decarburization; salt baths are the older route.
Heat Treating	GoodGood	Only at a shop set up for high-speed steel: the hardening window is narrow and it needs three tempers.
Nitriding	GoodGood	A shallow nitrided or nitrocarburized case on taps, drills and punches adds wear resistance; keep it thin so edges do not chip.
Black Oxide	GoodGood	Steam oxide or black oxide on drills and taps holds cutting fluid and reduces built-up edge and galling.
Annealing	GoodGood	Required before any re-hardening: re-hardening hardened HSS without a full anneal gives a coarse, brittle grain (a fish-scale fracture).
Welding	PoorPoor	Repair is rarely worth it; in production, HSS bodies are friction welded to carbon steel shanks before heat treatment.
Carburizing	Not recommendedNot recommended	Already carbon-rich with hard alloy carbides; extra surface carbon makes edges brittle and can melt the surface at the hardening temperature. Use nitriding or a PVD coating for more wear.

Design and sourcing tips

Specify grade, hardness and tempering ("M2, 62-64 HRC, triple tempered") and send it to a heat treater that runs high-speed steel; the hardening window is only a few tens of degrees wide.
For punches and cold work tools, ask for a lower hardening temperature and 60-62 HRC: toughness goes up and chipping goes down.
Rough machine annealed and leave about 0.2-0.4 mm (0.008-0.015") per side for grinding after hardening.
Add a PVD coating (TiN, TiAlN) or a steam oxide to cutting tools; either adds life for little cost.
If carbide is chipping in an interrupted cut or on a light, less rigid machine, M2 or cobalt M42 is the tougher fallback.

Frequently asked questions

What is M2 high-speed steel?: The most common grade of high-speed steel (HSS): a tool steel alloyed with about 6% tungsten, 5% molybdenum, 4% chromium and 2% vanadium. Hardened and triple tempered to 60-65 HRC, it keeps its hardness when the cutting edge runs hot, which is why drills, taps, end mills, reamers and broaches are made from it. "HSS" on a drill or tap usually means M2 or a close relative unless it says cobalt.
What is red hardness?: The ability of a steel to keep its hardness while hot, up to a dull red heat. Plain carbon and low-alloy tool steels start softening above about 200 °C (400 °F). M2 keeps its hardness until roughly its tempering temperature, around 540-595 °C (1,000-1,100 °F), because its tungsten, molybdenum and vanadium carbides resist softening. That is what lets HSS cut faster than carbon steel tools; carbide goes further still.
M2 vs M42: what is the difference?: M42 adds about 8% cobalt and more carbon. It hardens a few points higher and holds its hardness at higher cutting temperatures, so it lasts longer in stainless steel, titanium, nickel alloys and hard steels. It is more brittle and costs more. M2 is the general-purpose choice; M42, or M35 with about 5% cobalt, is for hard-to-machine materials.
M2 vs D2 for punches?: M2 has higher compressive strength and better wear resistance at the same or higher hardness, so it holds an edge longer on thin, hard or abrasive stock and at high press speeds. D2 is cheaper, easier to heat treat and easier to wire-cut in large die sections. Many shops make the die in D2 and the small punches, the ones that wear or mushroom in D2, in M2.
Can M2 be welded?: Not practically as a repair. The high alloy and carbon content make the weld and heat-affected zone crack unless the tool is preheated to roughly 500-550 °C (930-1,020 °F) and re-tempered, and a broken HSS tool is usually cheaper to replace. In production, drills and reamers are often made by friction or butt welding an M2 body to a carbon steel shank before heat treatment.

Processes that commonly use it

Wire EDM Sinker EDM CNC Grinding Centerless Grinding Vacuum Heat Treating

Related materials

D2 Tool Steel A2 Tool Steel H13 Tool Steel S7 Tool Steel 52100 Steel

Where to verify these values

ASTM A600 (high-speed tool steels)
Producer data sheets: Crucible M2, Böhler S600 (1.3343)
ASM Handbook Vol. 4, Heat Treating (high-speed steel hardening and tempering)
Roberts, Krauss and Kennedy, Tool Steels, 5th ed. (ASM International)

M2 High-Speed Tool Steel

Also: AISI M2, UNS T11302, W.Nr. 1.3343, DIN 1.3343, HS6-5-2, HS6-5-2C, SKH51 (JIS), Böhler S600, M2 HSS, high-speed steel, HSS, M-2

M2 is the general-purpose high-speed steel: 60-65 HRC with red hardness, for drills, taps, end mills, broaches and wear-resistant punches.

ASTM A600 (high-speed tool steels)ISO 4957 / EN ISO 4957 (HS6-5-2C)

At a glance

M2 High-Speed Tool Steel typical properties
Density	8.16 g/cm³ (0.295 lb/in³)
Tensile strength	About 760-880 MPa (110-128 ksi) annealed, estimated from hardness. Not a published property at 60-65 HRC, where M2 is rated by hardness, red hardness and compressive strength.
Yield strength	n/a: tensile yield is not commonly published for hardened M2, which fractures with almost no plastic strain in tension.
Hardness	About 220-255 HB annealed; 60-65 HRC working hardness (62-65 HRC typical for cutting tools)
Elongation	Not meaningful at working hardness (near zero in tension); tools are designed around hardness and edge toughness
Modulus of elasticity	215 GPa (31 Msi)
Thermal	Hardened from 1,175-1,230 °C (2,150-2,250 °F), close to its incipient melting point; red hardness: resists softening in service up to roughly its 540-595 °C (1,000-1,100 °F) tempering temperature
Composition	Fe, 0.78-0.88% C (0.95-1.05% in high-carbon M2), 5.50-6.75% W, 4.50-5.50% Mo, 3.75-4.50% Cr, 1.75-2.20% V

MachinabilityFair

About 50% of the W1 (1% carbon tool steel) benchmark annealed: abrasive and slow. Rough machine annealed, harden, then grind; hardened M2 is ground or wire-cut, not machined.

WeldabilityPoor

Not a welding grade. Broken HSS tools are rarely worth repairing; if attempted, preheat to roughly 500-550 °C (930-1,020 °F) and temper after. Drills and reamers are often made by friction welding an HSS body to a carbon steel shank, a controlled production process.

FormabilityPoor

Machined and ground from bar, flat and blanks; not formed.

Corrosion resistancePoor

Rusts; tools are protected with steam oxide, black oxide, PVD coatings or oil.

Heat treatment

Process compatibility

How M2 takes each process, and what to specify. Each process links to its own guide and to the shops that do it.

M2 High-Speed Tool Steel process compatibility
Process	Rating	Notes
CNC Grinding	ExcellentExcellent	The main process for M2: tools and punches are ground to finish after hardening. Use aluminum oxide or CBN wheels with flood coolant; grinding burn softens and cracks the edge.
Centerless Grinding	GoodGood	Drill blanks, pins, punches and drill rod are centerless ground.
CNC Machining	FairFair	Annealed only, and slow; rough machine, harden, then grind.
Wire EDM	GoodGood	Cuts hardened punches and form tools; remove the recast layer from cutting edges.
Sinker EDM	GoodGood	Forms cavities and shapes in hardened punches and dies; skim off the white layer.
Vacuum Heat Treating	ExcellentExcellent	Vacuum furnaces with a high-pressure gas quench handle the 1,200 °C cycle cleanly with no decarburization; salt baths are the older route.
Heat Treating	GoodGood	Only at a shop set up for high-speed steel: the hardening window is narrow and it needs three tempers.
Nitriding	GoodGood	A shallow nitrided or nitrocarburized case on taps, drills and punches adds wear resistance; keep it thin so edges do not chip.
Black Oxide	GoodGood	Steam oxide or black oxide on drills and taps holds cutting fluid and reduces built-up edge and galling.
Annealing	GoodGood	Required before any re-hardening: re-hardening hardened HSS without a full anneal gives a coarse, brittle grain (a fish-scale fracture).
Welding	PoorPoor	Repair is rarely worth it; in production, HSS bodies are friction welded to carbon steel shanks before heat treatment.
Carburizing	Not recommendedNot recommended	Already carbon-rich with hard alloy carbides; extra surface carbon makes edges brittle and can melt the surface at the hardening temperature. Use nitriding or a PVD coating for more wear.

Design and sourcing tips

Specify grade, hardness and tempering ("M2, 62-64 HRC, triple tempered") and send it to a heat treater that runs high-speed steel; the hardening window is only a few tens of degrees wide.

For punches and cold work tools, ask for a lower hardening temperature and 60-62 HRC: toughness goes up and chipping goes down.

Rough machine annealed and leave about 0.2-0.4 mm (0.008-0.015") per side for grinding after hardening.

Add a PVD coating (TiN, TiAlN) or a steam oxide to cutting tools; either adds life for little cost.

If carbide is chipping in an interrupted cut or on a light, less rigid machine, M2 or cobalt M42 is the tougher fallback.

Frequently asked questions

What is M2 high-speed steel?

The most common grade of high-speed steel (HSS): a tool steel alloyed with about 6% tungsten, 5% molybdenum, 4% chromium and 2% vanadium. Hardened and triple tempered to 60-65 HRC, it keeps its hardness when the cutting edge runs hot, which is why drills, taps, end mills, reamers and broaches are made from it. "HSS" on a drill or tap usually means M2 or a close relative unless it says cobalt.

What is red hardness?

The ability of a steel to keep its hardness while hot, up to a dull red heat. Plain carbon and low-alloy tool steels start softening above about 200 °C (400 °F). M2 keeps its hardness until roughly its tempering temperature, around 540-595 °C (1,000-1,100 °F), because its tungsten, molybdenum and vanadium carbides resist softening. That is what lets HSS cut faster than carbon steel tools; carbide goes further still.

M2 vs M42: what is the difference?

M42 adds about 8% cobalt and more carbon. It hardens a few points higher and holds its hardness at higher cutting temperatures, so it lasts longer in stainless steel, titanium, nickel alloys and hard steels. It is more brittle and costs more. M2 is the general-purpose choice; M42, or M35 with about 5% cobalt, is for hard-to-machine materials.

M2 vs D2 for punches?

M2 has higher compressive strength and better wear resistance at the same or higher hardness, so it holds an edge longer on thin, hard or abrasive stock and at high press speeds. D2 is cheaper, easier to heat treat and easier to wire-cut in large die sections. Many shops make the die in D2 and the small punches, the ones that wear or mushroom in D2, in M2.

Can M2 be welded?

Not practically as a repair. The high alloy and carbon content make the weld and heat-affected zone crack unless the tool is preheated to roughly 500-550 °C (930-1,020 °F) and re-tempered, and a broken HSS tool is usually cheaper to replace. In production, drills and reamers are often made by friction or butt welding an M2 body to a carbon steel shank before heat treatment.