Steel M7
AISI/SAE M7 · UNS T11307 · JIS SKH58
M7 is a molybdenum-type high-speed steel (T11307, SKH58) that deep-hardens to 62–66 HRC and keeps working hardness to about 500 °C.
Reference datasheet — M7 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
M7 tempers and conditions
M7 is supplied in 5 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefault Annealed | Standard supply condition for machining tool blanks before hardening; max 255 HB. | 520 | 830 | 18 | 235 HB | — |
Cold drawn / centreless ground, annealed | Precision-ground annealed rod for drills and taps where a size-to-tolerance blank is needed. | 600 | 880 | 14 | 23 HRC | 3.1 % IACS |
Hardened & tempered, 62–64 HRC | Toughness-biased working hardness for taps, reamers and larger drills; austenitize ~1190 °C, triple temper 540–560 °C. | 1,950 | 2,200 | 1 | 63 HRC | 23 W/m·K |
Hardened + steam/nitride/PVD surface treated | Hardened tool with a surface layer (steam oxide, nitride or TiN/TiAlN) for higher tool life on abrasive or gummy work. | 2,100 | 2,400 | 1 | 64 HRC | 2.8 % IACS |
Hardened & tempered, 64–66 HRC | Peak-hardness condition for small drills, saw segments and punches cutting abrasive materials; lowest toughness. | 2,400 | 0.5 | 65 HRC | — |
What is M7?
M7 is a molybdenum-type high-speed steel (T11307, SKH58) that deep-hardens to 62–66 HRC and keeps working hardness to about 500 °C. It is used for drills, taps, reamers and punches, and is stocked as annealed or cold-drawn annealed bar at roughly 520 MPa yield, 830 MPa tensile, 18% elongation, 235 HB and 207 GPa modulus before heat treatment. Corrosion resistance is low (score 18) and the steel is effectively non-weldable, so hardened parts are finished by grinding or EDM only. M2 is the closest general-purpose alternative in the same family. M7 has a density of 7.95 g/cm³ (0.287 lb/in³), heavier than 94% of steel grades. It melts at 1,250°C (2,282 °F). M7 has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 67% of steel grades. Elongation at break is 18% and the elastic modulus is 207 GPa (30 Msi).
What is M7 used for?
- Twist drills
- Taps and reamers
- General machine-shop cutting tools
- Punches
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
- High embodied carbon — 3.3 kg CO₂/kg, worse than 92% of steel grades
- Poor heat conductor — 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
M7 properties
Typical room-temperature values for M7-ANN; bars are the position among steel grades.
Physical3
M7 has a density of 7.95 g/cm³ (0.287 lb/in³), heavier than 94% of steel grades. It melts at 1,250°C (2,282 °F).
Mechanical16
M7 has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 67% of steel grades. Elongation at break is 18% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
M7 is rated for continuous service to 500°C (932 °F). It conducts heat at 24 W/m·K (13.9 BTU/hr·ft·°F), worse than 90% of steel grades. Thermal expansion is 10.9 µm/m·K (6.06 µin/in·°F).
Electrical3
M7 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (18/100), better than 83% of steel grades.
Sustainability4
Producing a kilogram of M7 takes about 44 MJ of energy and emits 3.3 kg of CO₂ — more than 92% of steel grades. Typical recycled content is 40%.
Manufacturability8
M7's machinability is poor (32/100, worse than 87% of steel grades); weldability not recommended (12/100); formability poor (15/100).
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. M7 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with M7
Is M7 easy to machine?
Machine only in the annealed condition with rigid setups, sharp cobalt-HSS or coated-carbide tools and generous coolant; hardened M7 needs grinding or EDM.
Can M7 be welded?
Essentially non-weldable structurally — repair welding only with matched HSS filler, 500–550 °C preheat and immediate re-temper.
Can M7 be formed, bent or molded?
Hot forge 1050–1150 °C (stop above 900 °C) and cool slowly to a full spheroidize anneal at 850–900 °C; no meaningful cold forming.
M7 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 | 0.97 – 1.05 | 1 |
| Mn | 0.15 – 0.4 | 0.3 |
| Si | 0.2 – 0.55 | 0.4 |
| Cr | 3.5 – 4 | 3.75 |
| Mo | 8.2 – 9.2 | 8.7 |
| W | 1.4 – 2.1 | 1.75 |
| V | 1.75 – 2.25 | 2 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on M7?
Protect from decarburization in vacuum, salt bath or controlled atmosphere during hardening; finish with grinding plus steam oxide, black oxide, nitriding or TiN/TiAlN PVD — no anodizing.
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel M7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- T11307
- JIS
- SKH58
How much does M7 cost?
M7 is a high-cost steel ($$$$), pricier than about 78% 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.
M7 — frequently asked
What is M7 used for?
M7 is typically used for twist drills, taps and reamers, general machine-shop cutting tools and punches. In short: deep-hardening molybdenum HSS; 62–66 HRC tool grade; drill and tap standard.
What is the yield strength of M7?
M7 has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 67% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is M7 easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Machine only in the annealed condition with rigid setups, sharp cobalt-HSS or coated-carbide tools and generous coolant; hardened M7 needs grinding or EDM.
Can M7 be welded?
Not readily — weldability is rated not recommended (12/100). Essentially non-weldable structurally — repair welding only with matched HSS filler, 500–550 °C preheat and immediate re-temper.
What surface finishes work on M7?
Protect from decarburization in vacuum, salt bath or controlled atmosphere during hardening; finish with grinding plus steam oxide, black oxide, nitriding or TiN/TiAlN PVD — no anodizing.
Can M7 be formed, bent or molded?
Hot forge 1050–1150 °C (stop above 900 °C) and cool slowly to a full spheroidize anneal at 850–900 °C; no meaningful cold forming.
What is the maximum service temperature of M7?
M7 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between M7-ANN and M7 HT-N?
ANN is the default condition — standard supply condition for machining tool blanks before hardening; max 255 HB. HT-N: hardened tool with a surface layer (steam oxide, nitride or TiN/TiAlN) for higher tool life on abrasive or gummy work. Yield strength is 520 MPa in ANN versus 2,100 MPa in HT-N.
How much does M7 cost?
M7 is a high-cost steel ($$$$), pricier than about 78% 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.
Sources
- ASTM A600 — Tool Steel, High Speed — ASTM International (2021)
- JIS G 4403 (SKH58) — JSA (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Tool Steels) — ASM International (1990)
- Tool Steels, 5th ed. (Roberts, Krauss, Kennedy) — ASM International (1998)
- High-speed steel grade datasheets (M2/M7 class) — Erasteel / Böhler / Crucible (2022)
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.