M7 Tool Steel
Molybdenum high-speed steel
Typical values for the temper in the title
M7 is a molybdenum high-speed steel (about 8.7% molybdenum and a little tungsten), with higher carbon and vanadium than M1. The result: higher hardness and wear resistance than M2, with good toughness, at a relatively low price thanks to molybdenum instead of tungsten.
It is especially common in drills and end mills, and also in broaches and turning tools. In JIS it is SKH58.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Modulus of elasticity E | 210 GPa | |
| Density ρ | 7.95 g/cm³ | |
| Hardness after hardening | HRC 63–66 | |
| Machinability | 25% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | 0.97–1.05 | hardness |
| Mo molybdenum | 8.20–9.20 | hot hardness |
| W tungsten | 1.40–2.10 | |
| V vanadium | 1.75–2.25 | carbides |
| Cr chromium | 3.50–4.00 | hardenability |
Ranges per ASTM A600 (T11307).
Heat treatment
Tool steels are supplied annealed (soft, for machining), and get their hardness by hardening and tempering after machining. The final hardness is chosen by the balance between wear resistance and toughness.
| Step / condition | Values | Notes |
|---|---|---|
| Annealed | easy to machine | making the tool |
| Hardened and double tempered | HRC 63–66 | the finished tool |
Applications
- Drills
- End mills
- Broaches
- Turning tools
- Punches
Fabrication
Machining and grinding
Machine in the annealed state, leave a grinding allowance after hardening, and grind carefully so as not to overheat and crack the surface.
Hardening
From a high temperature, with double or triple temper. Molybdenum steels are sensitive to surface decarburization, so harden in a controlled atmosphere.
Coating
PVD coating (TiN, TiAlN) is common to extend life.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| M2 | — / — | Not recommended | M2: the common high-speed steel · material page |
| M42 | 3800-4100 / — | Not recommended | M42: with cobalt, higher hot hardness · material page |
| ASP 2023 | — / — | Not recommended | ASP 2023: a PM high-speed steel, tougher · material page |
Common mistakes
Hardening without a controlled atmosphere
The surface loses carbon and becomes soft.
Tempering only once
Retained austenite remains. Temper at least twice.
Choosing M7 for very hot cutting
Cobalt grades are better.
Equivalents, standards and supply
| JIS | SKH58 |
|---|---|
| UNS | T11307 |
| Standards | ASTM A600 |
| Forms | bar · plate · flat |
| Producers | Carpenter · Latrobe |
Learn more
Values are typical and for comparison only. Actual hardness depends on hardening temperature, section size and tempering. For design, rely on the standard, the producer data sheet and the mill certificate. Sources: ASTM A681 and A600, ISO 4957, and producer data sheets (Crucible, Niagara, Alro).
Updated: October 31, 2026