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K390 offers greater abrasive edge retention, while MagnaCut combines more toughness with much higher corrosion resistance. If you enjoy a wear-focused non-stainless blade and accept its care, K390 has a clear purpose. MagnaCut asks less of you around moisture.
Performance Ratings
For the science, we turn to Dr. Larrin Thomas of Knife Steel Nerds, who has kindly allowed us to share his ratings here.
The toughness score of 7 is for original Crucible MagnaCut. In written feedback to KnifeInformer, Dr. Thomas provided a toughness rating of 8.5 for Erasteel MagnaCut; his January 2026 testing explains the differences between the two versions. This table uses the original version.
| Property | Böhler K390 Microclean | CPM MagnaCut |
|---|---|---|
| Abrasive edge retention | ||
| Toughness | ||
| Corrosion resistance |
Heat treatment, hardness and geometry affect actual knives.
K390 Has the Wear Advantage
K390 rates 7.5 for abrasive edge retention and MagnaCut 5. We would lean toward K390 for frequent abrasive slicing when rust care is manageable.
That difference does not establish a fixed cutting-time ratio. Edge geometry and treatment still affect how a finished knife wears.
Our K390 steel profile explains its properties and care in more detail.
MagnaCut Retains More Toughness
Original MagnaCut rates 7 for toughness against K390 at 6. The K390 number includes Dr. Thomas’s correction to his earlier 5.5 score.
The separate Erasteel MagnaCut update is identified in the rating note. Do not mix production versions while explaining the difference.
Our MAGNACUT steel profile explains its properties and care in more detail.
The Corrosion Difference Is Much Larger
MagnaCut rates 9.5 for corrosion resistance and K390 rates 4. K390 is not stainless and needs more attention to drying and storage.
For a knife carried through humid days or used around food and water, MagnaCut may be the more convenient material despite K390’s wear advantage.
Choose K390 for a Real Wear Need
We would choose K390 when abrasive dulling is a persistent limitation and the maintenance is acceptable. We would take MagnaCut for a broader balance with less rust concern.
Neither choice should override an unsuitable blade design. Start with the knife you need, then decide which material compromise fits.
Composition
Our steel composition guide explains the elements and the differences between reported values, ranges and limits.
Böhler K390 Microclean: Böhler K390 Microclean average composition, mass %; not a finished-blade assay. Böhler: K390 Microclean.
CPM MagnaCut: Niagara typical composition, mass %; selected elements, not a batch analysis. Niagara Specialty Metals: CPM MagnaCut.
| Element | Böhler K390 Microclean | CPM MagnaCut |
|---|---|---|
| Carbon (C) | 2.47% | 1.15% |
| Chromium (Cr) | 4.2% | 10.7% |
| Molybdenum (Mo) | 3.8% | 2% |
| Vanadium (V) | 9% | 4% |
| Tungsten (W) | 1% | Not listed |
| Cobalt (Co) | 2% | Not listed |
| Silicon (Si) | 0.55% | Not listed |
| Manganese (Mn) | 0.4% | Not listed |
| Niobium (Nb) | Not listed | 2% |
| Nitrogen (N) | Not listed | 0.2% |
Compare Two Knife Steels
Sources and Update Notes
- Dr. Larrin Thomas: knife steel ratings · Property ratings; the scores describe steels rather than individual finished knives.
- Böhler: K390 Microclean
- Niagara Specialty Metals: CPM MagnaCut
