Abrasives
Grinding and Sharpening CPM M4: Belt Recommendations & Technique
CPM M4 sits at the top of this database’s “hardest to grind” list, alongside CPM 20CV and CPM S30V. Its heavy vanadium and tungsten carbide load, adapted…
Knife steel
CPM M4 knife steel
A high-speed tool steel with extreme edge retention thanks to a heavy vanadium and tungsten carbide load, popular for hard-use fixed blades where long edge life matters more than rust resistance.
Also known as
At a glance
How CPM M4 behaves
The four meters are relative to the rest of the database. Composition is the published nominal analysis, not a mill certificate for your bar.
Working properties
- Toughness
- 3
- Edge retention
- 5
- Corrosion resistance
- 1
- Ease of grinding
- 2
- Composition
- 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
At the bench
What each property means for this steel
Open the property you are worried about. Every note is written for the blade in your hand, not for a spec sheet.
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.
Grinding and machinability
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.
The full reference
More on 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 up 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.
Head to head
Compare steel data for CPM M4
Every matchup CPM M4 appears in, dimension by dimension.
Keep reading
Guides that use this steel
MetallurgyWhat Alloying Elements Do: Carbon, Chromium, Vanadium & More
Every knife steel is iron plus a specific recipe of other elements, and each of those elements pulls the steel’s behavior in a particular direction…
MetallurgyCarbide Size and Sharpening: Why Some Steels Feel Different
Two steels with similar hardness numbers can feel completely different under a sharpening stone, one glides along smoothly, another feels like it’s…
Same bench
Grind CPM M4 on a machine that holds still
Whatever the steel, the grind is only as flat as the platen behind it. I machine the parts, hand-assemble and test Torus grinders in Sterling, Illinois.
Nova 2×72 Aluminum Belt Grinder
Current dual-axis platform with a fiber-laser-cut 6061 chassis and single-knob tracking.
Starts at$1,295
Nebula 2×72 Steel Belt Grinder
Current dual-axis platform with a steel chassis, more mass and less vibration.
Starts at$1,295
Torus 2×72 Classic Aluminum Belt Grinder
Prior-design aluminum chassis, 90-degree tilt and 1.5-inch tooling arms.
Starts at$995
One-man shop
Thinking about CPM M4?
Tell me what the blade is for and how you heat treat. I will tell you whether this is the steel I would use, and what I would use instead.