Steel M42
AISI/SAE M42 · UNS T11342 · EN 1.3247, S2-10-1-8 · GB W2Mo9Cr4VCo8
M42 is a molybdenum-series high-speed tool steel with about 8 % cobalt (AISI M42 / DIN 1.3247 / HS2-9-1-8, SKH59, W2Mo9Cr4VCo8) that reaches 67–70 HRC after hardening and tempering, with red hardness and wear resistance clearly above M2.
Values for the Annealed condition
M42 tempers and conditions
M42 is supplied in 3 conditions, soft to hard. Annealed is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AnnealedDefault soft annealed (spheroidized) supply condition | Standard mill supply condition for bar, plate and blanks — machine/grind to shape before hardening. | 620 | 900 | 12 | 25 HRC | 3.1 % IACS |
Maximum hardness | Pick for maximum wear resistance in small, rigidly supported tools (form tools, thread taps, razor/knife blades); very brittle. | 1,800 | 1,900 | 0 | 69 HRC | 2.6 % IACS |
Quenched and tempered | Toughness-biased working hardness for larger cutters, punches and interrupted cutting. | 2,400 | 0 | 65 HRC | — |
Supply forms, finishes and certifications
Ways M42 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
H&T + PVD TiN | H&T + PVD coated | Surface finish |
What is M42?
M42 is a molybdenum-series high-speed tool steel with about 8 % cobalt (AISI M42 / DIN 1.3247 / HS2-9-1-8, SKH59, W2Mo9Cr4VCo8) that reaches 67–70 HRC after hardening and tempering, with red hardness and wear resistance clearly above M2. It is chosen for drills, taps, milling cutters, inserts and cold-work punches that cut high-strength alloy steel, titanium and nickel-base superalloys, and is supplied mainly as annealed bar and tool blanks. The limits are lower toughness and edge-chipping resistance, a narrow grinding and heat-treatment window, higher cost from the cobalt content, and essentially no corrosion resistance. M2 is the tougher, lower-cost alternative. M42 has a density of 7.98 g/cm³ (0.288 lb/in³), heavier than 94% of steel grades. It melts at 1,290°C (2,354 °F). M42 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 78% of steel grades. Elongation at break is 12% and the elastic modulus is 222 GPa (32.2 Msi).
What is M42 used for?
- Twist drills for high-strength alloy steel
- End mills and milling cutters
- Taps and thread-cutting tools
- Form tools and cutting inserts
- Reamers and broaches
- Cold-work die punches
- Metal-cutting saw blades
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- High strength — 620 MPa (89.9 ksi), better than 78% of steel grades
Limitations
- Low fracture toughness — 33 MPa·√m (30 ksi·√in), worse than 95% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- High embodied carbon — 4.4 kg CO₂/kg, worse than 95% of steel grades
- Poor heat conductor — 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
M42 properties
Typical room-temperature values for M42-Annealed; bars are the position among steel grades.
Physical3
M42 has a density of 7.98 g/cm³ (0.288 lb/in³), heavier than 94% of steel grades. It melts at 1,290°C (2,354 °F).
Mechanical17
M42 has a yield strength of 620 MPa (89.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 78% of steel grades. Elongation at break is 12% and the elastic modulus is 222 GPa (32.2 Msi).
Thermal5
M42 is rated for continuous service to 400°C (752 °F). It conducts heat at 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades. Thermal expansion is 10.8 µm/m·K (6 µin/in·°F).
Electrical3
M42 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of M42 takes about 62 MJ of energy and emits 4.4 kg of CO₂ — more than 96% of steel grades. Typical recycled content is 30%.
Manufacturability8
M42's machinability is fair (38/100, worse than 80% of steel grades); weldability poor (20/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. M42 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with M42
Is M42 easy to machine?
Machine only in the annealed state with rigid setups, low speeds and generous coolant; hardened M42 must be ground or EDM'd (grind with SG/CBN wheels, avoid burn and grinding cracks).
Can M42 be welded?
Not a weldable structural steel — repair-weld only with matched HSS/Co filler, 500–550 °C preheat and immediate re-temper to avoid cracking.
Can M42 be formed, bent or molded?
Hot work 1100→900 °C with slow controlled cooling; cold forming is impractical. Harden 1170–1190 °C (salt/vacuum), oil or gas quench, then temper 3× at 540–560 °C, 1 h each.
Manufacturability
The process limits FabDigit applies to M42. Every M42 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair38 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
M42 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 1.05 – 1.15 | 1.1 |
| Si | 0.15 – 0.65 | 0.35 |
| Mn | 0.15 – 0.4 | 0.28 |
| Cr | 3.5 – 4.25 | 3.9 |
| Mo | 9 – 10 | 9.5 |
| W | 1.15 – 1.85 | 1.5 |
| V | 0.95 – 1.35 | 1.15 |
| Cogives red hardness | 7.75 – 8.75 | 8.25 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on M42?
Not anodizable; use black oxide, steam tempering, phosphate or PVD TiN/TiAlN for wear and corrosion protection; oil-film protect all bare stock.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel M42 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T11342
- EN / DIN / Werkstoff-Nr.
- 1.3247S2-10-1-8
- GB (China)
- W2Mo9Cr4VCo8
- Similar grades
- SKH59
How much does M42 cost?
M42 is a specialty-cost steel ($$$$$), pricier than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
M42 — frequently asked
What is M42 used for?
M42 is typically used for twist drills for high-strength alloy steel, end mills and milling cutters, taps and thread-cutting tools, form tools and cutting inserts, reamers and broaches and cold-work die punches. In short: ultimate cutting hardness.
What is the yield strength of M42?
M42 has a typical yield strength of 620 MPa (89.9 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 78% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is M42 easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Machine only in the annealed state with rigid setups, low speeds and generous coolant; hardened M42 must be ground or EDM'd (grind with SG/CBN wheels, avoid burn and grinding cracks).
Can M42 be welded?
Not readily — weldability is rated poor (20/100). Not a weldable structural steel — repair-weld only with matched HSS/Co filler, 500–550 °C preheat and immediate re-temper to avoid cracking.
What surface finishes work on M42?
Not anodizable; use black oxide, steam tempering, phosphate or PVD TiN/TiAlN for wear and corrosion protection; oil-film protect all bare stock.
Can M42 be formed, bent or molded?
Hot work 1100→900 °C with slow controlled cooling; cold forming is impractical. Harden 1170–1190 °C (salt/vacuum), oil or gas quench, then temper 3× at 540–560 °C, 1 h each.
What is the maximum service temperature of M42?
M42 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does M42 cost?
M42 is a specialty-cost steel ($$$$$), pricier than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in M42?
Yes — M42 is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A600 — Tool Steel High Speed Tool Steels — ASTM International (2021)
- EN ISO 4957 — Tool steels (1.3247 / HS2-9-1-8) — ISO/CEN (2018)
- GB/T 9943 — (W2Mo9Cr4VCo8) — SAC (2008)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Tool Materials — ASM International (1995)
- Böhler S500 (M42) high speed steel datasheet — voestalpine Böhler Edelstahl (2022)
- Erasteel ASP/HSS grade data (M42) — Erasteel (2021)
- M42/W2Mo9Cr4VCo8 (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.