CPM M4
CPM M4 is a high-speed tool steel adapted from industrial cutting-tool applications into one of the highest wear-resistance options available to knifemakers. Its heavy vanadium and tungsten carbide load gives it exceptional edge retention, at the cost of no meaningful corrosion resistance and a heat treat that runs hotter and more involved than most knife steels.
CPM M4 FAQ
Is CPM M4 stainless?
No, with only 4% chromium it is well below the stainless threshold and needs the same oiling and drying care as any carbon tool steel.
What hardness does CPM M4 reach?
Typically 62-64 Rc, with a maximum near 65 Rc. See the heat treat details further down this page for the full recipe.
Is CPM M4 hard to sharpen?
Yes, it is one of the most demanding steels in this database to sharpen due to its very heavy carbide content. Diamond stones are strongly recommended. See the full grinding and sharpening guide.
How does CPM M4 compare to CPM 3V or CPM CruWear?
CPM M4 offers substantially better edge retention than both, at a real cost in toughness and ease of grinding. See the full breakdowns: CPM 3V vs CPM M4 and CPM CruWear vs CPM M4.
Also known as: CPM M4, CPM Rex M4
Composition
| Carbon (C) | 1.42% |
| Chromium (Cr) | 4.00% |
| Molybdenum (Mo) | 5.25% |
| Vanadium (V) | 4.00% |
| Tungsten (W) | 5.50% |
Properties
| Property | Rating | Notes |
|---|---|---|
| Toughness | ★★★☆☆ | Decent for a steel with this much carbide content, but it trades some toughness for its extreme wear resistance; not in the same class as CPM 3V or CruWear for impact resistance. |
| Edge Retention | ★★★★★ | Among the best edge retention available in a non-stainless steel, thanks to a very heavy load of hard vanadium and tungsten carbides. A favorite where long edge life is the top priority. |
| Corrosion Resistance | ★☆☆☆☆ | Only 4% chromium, well below the stainless threshold. Needs the same oiling and drying care as a plain carbon steel. |
| Machinability / Grinding | ★★☆☆☆ | The heavy carbide load makes it noticeably harder on belts than simple carbon or basic stainless steels, though the powder-metallurgy process makes it more workable than conventional high-speed steel. |
Heat Treatment
Preheat at 1500-1550 F, then austenitize between 1900 and 2150 F depending on the desired balance: lower temperatures favor toughness, higher temperatures maximize wear resistance at some cost to toughness. Quench in oil, air, salt, or plate to below 125-150 F. Double or triple temper at 1000-1050 F, holding at least 2 hours per cycle, to fully convert retained austenite through secondary hardening. Typical knife hardness lands around 62-64 Rc, with a maximum near 65 Rc.
Best Uses
A strong choice for hard-use fixed blades, competition cutting knives, and high-end kitchen knives where extreme edge retention outweighs the need for corrosion resistance. Browse more entries in the Knife Steel Database, and see the Heat Treating Guide for the full stage-by-stage process.
Sources: Crucible Industries CPM M4 / CPM Rex M4 HC datasheet; MW Alloys CPM M4 steel technical summary.