CPM M4 is a high-speed tool steel that has become a favorite for hard-use performance knives. Spyderco’s Gayle Bradley models are well-known examples.
CPM M4 Steel at a Glance
| Type | Powder metallurgy (PM) steel |
|---|---|
| Made by | Crucible (USA) |
| Typical hardness | 61-64 HRC |
| Key elements | Carbon about 1.4%, chromium about 4%, molybdenum about 5.25%, vanadium about 4%, tungsten about 5.5% |
| Edge retention | 8/10 (very good) |
| Toughness | 6/10 (good) |
| Rust resistance | 2/10 (low) |
| Ease of sharpening | 3/10 (hard) |
| Best for | Hard-use performance |
Ratings are relative 1 to 10 scores for typical factory heat treatments. See how CPM M4 ranks against 46 other steels in our Knife Steel Chart.
What Is CPM M4 Steel?
M4 was made for industrial cutting tools. Its tungsten, molybdenum and vanadium carbides give high wear resistance, and the powder process keeps it tough.
CPM M4 Steel Properties
- Edge retention: Very good.
- Toughness: Good.
- Rust resistance: Low. Keep it dry and lightly oiled.
- Ease of sharpening: Hard. Use diamond or CBN stones.
CPM M4 vs Other Steels
CPM M4 vs CPM 3V
Compared with CPM 3V, CPM M4 holds an edge longer. CPM 3V is tougher, resists rust slightly better and is easier to sharpen. Read our CPM 3V guide.
CPM M4 vs CruWear
Compared with CruWear, CPM M4 holds an edge slightly longer. CruWear is tougher, resists rust slightly better and is slightly easier to sharpen. Read our CruWear guide.
CPM M4 vs Böhler K390
Compared with Böhler K390, CPM M4 is slightly easier to sharpen. Böhler K390 holds an edge slightly longer and is slightly tougher. Read our Böhler K390 guide.
Is CPM M4 Steel Good for Knives?
Yes, for hard-use EDC and work knives. Keep it dry, or choose a coated blade.
Pros:
- Very good edge retention
- Good toughness
Cons:
- Rusts easily
- Hard to sharpen
Knives That Use CPM M4 Steel
Makers sometimes change blade steels between versions, so check the listing to confirm the steel before you buy.
Frequently Asked Questions
Is CPM M4 steel stainless?
No. CPM M4 is not stainless and will rust or patina if left wet. Keep it dry and lightly oiled.
How hard is CPM M4 steel?
Knives in CPM M4 are usually heat treated to around 61-64 HRC.
Is CPM M4 easy to sharpen?
Hard. Diamond or CBN stones work best.
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