CPM MagnaCut, is a new knife steel developed by Dr. Larrin Thomas in collaboration with Crucible Industries through powder metallurgy.
CPM SPY 27 steel is also a relatively new steel that is an exclusive spyderco knife steel jointly developed by Spyderco and Crucible industries through powder metallurgy.
MagnaCut uses an innovative approach that eliminates chromium carbides,it boasts a unique microstructure consisting of fine, high-hardness vanadium and niobium carbides.
This microstructure, enables MagnaCut to achieve exceptional high toughness and corrosion resistance that surpasses SPY27 steel and other conventional stainless steels.
MagnaCut vs SPY27 Steel At A Glance
| Property | MagnaCut Steel | SPY27 Steel |
|---|---|---|
| Hardness | Can achieve over 65 HRC | Maximum hardness around 64 HRC |
| Toughness | Significantly higher toughness | Toughness lower than MagnaCut. |
| Edge Retention / Wear Resistance | Very good edge retention. | Lower edge retention than MagnaCut. |
| Corrosion Resistance | Outstanding corrosion resistance, | Very Good but lower than MagnaCut. |
| Grindability / Sharpening | Ease of sharpening better than SPY27 | Slightly lower than MagnaCut |
Toughness
MagnaCut steel exhibits higher toughness compared to SPY27 steel, making it more resistant to chipping and breaking, especially for larger knife blades.
The high toughness of MagnaCut is achieved through its unique microstructure, which eliminates chromium carbides and consists of only small, high-hardness vanadium and niobium carbide content.
This fine carbide structure results in improved toughness values similar to non-stainless steels like CPM-4V and Vanadis 4 Extra, which are well-regarded for their excellent toughness.
In contrast, SPY27 steel displays toughness levels comparable to S35VN, which are lower than the exceptional toughness exhibited by MagnaCut.
SPY27 steel toughness is expected to be better than S45VN and at least as good as S35VN.
This is likely due to the presence of chromium carbides in its microstructure.
For larger knives, the exceptional toughness of MagnaCut makes it especially suitable, as it reduces the risk of chipping and breaking under demanding conditions.
High toughness allows for the production of fine cutting knives with thinner edges and more acute angles.
This enhancing their cutting ability while minimizing the susceptibility to chipping, ultimately leading to improved edge retention.
Hardness
MagnaCut steel can typically achieve higher hardness levels than SPY27 steel.
MagnaCut data sheet shows that with various heat treatment conditions, it can reach hardness levels over 65 HRC with certain austenitizing temperatures and cryogenic treatments.
In contrast, SPY27 steel can reach a maximum hardness of around 64 HRC with cryogenic treatments.
However, for knife applications, the recommended aim hardness for both steels is typically lower, in the range of 60-62 HRC.
This is to strike a balance between hardness for edge retention and toughness to prevent chipping or breaking.
The MagnaCut data sheet recommends an aim hardness of 60-63 HRC.
Similarly, the SPY27 with a heat treatment leading to around 60 HRC would provide good hardness while maintaining toughness.
Edge Retention
MagnaCut steel demonstrates superior edge retention and wear resistance compared to SPY27 steel especially at higher hardness levels.
This makes MagnaCut steel an excellent choice for knives that demand exceptional edge-holding capabilities.
The CATRA edge retention testing, a standard measure of relative wear resistance, reveals that MagnaCut at 62.5 HRC has a rating of 135% compared to 440C stainless steel.
Contrary, SPY27 is expected to have slightly lower edge retention than S35VN, which rates at 130% at 61 HRC.
MagnaCut steel true edge retention potential is realized when treated at higher hardness levels.
The MagnaCut data sheet indicates that it can achieve hardness levels exceeding 65 HRC, which would result in significantly improved wear resistance and edge retention.
In contrast, SPY27 steel maximum hardness is limited to around 64 HRC, restricting its edge retention capabilities at higher hardness levels.
The exceptional edge retention of MagnaCut is attributed to its unique microstructure, which consists of fine, high-hardness vanadium and niobium carbides.
These carbides, formed due to the alloy composition of MagnaCut, contribute to superior wear resistance compared to the chromium carbides present in steels like SPY27.
Additionally, the absence of chromium carbides in MagnaCut knife steel microstructure enhances its toughness, further enhancing its edge-holding capabilities by reducing the risk of chipping or deformation.
Corrosion Resistance
MagnaCut stainless steel exhibits significantly better corrosion resistance compared to SPY27 stainless steel
making it an excellent choice for knives, especially those intended for use in or salt water.
The corrosion resistance of MagnaCut is outstanding, approaching but not quite equal to steels like Vanax and LC200N, which are renowned for their exceptional corrosion resistance.
This remarkable corrosion resistance is achieved through MagnaCut’s unique microstructure, which eliminates chromium carbides.
Eliminating CrC prevents the formation of chromium-depleted regions surrounding the carbides that can lead to localized corrosion.
In contrast, SPY27 steel has “good” or “above average” corrosion resistance, comparable to steels like S30V, it cannot match the corrosion resistance of MagnaCut or stainless steels like 420HC.
Spyderco, a renowned knife manufacturer, has incorporated MagnaCut steel into their elite Salt Series of knives designed for use in or around water.
MagnaCut is less corrosion-resistant than LC200N, but it offers the best edge retention of Spyderco’s Salt Series knife steels.
This makes MagnaCut a compelling choice for users who prioritize both corrosion resistance and edge retention in demanding environments.
Ease of sharpening
MagnaCut steel exhibits slightly better grindability and ease of sharpening compared to SPY27 steel, making it more desirable for knife makers and users alike.
According to knifemakers’ feedback, MagnaCut grinds and finishes more easily than steels like S35VN and S45VN, despite containing significant amounts of hard vanadium and niobium carbides.
The ease of sharpening MagnaCut knives can translate into more convenient maintenance and longer-lasting edges, further enhancing the overall user experience.
Final Thoughts on MagnaCut vs SPY27 Steel
Having extensively used and tested both SPY27 and MagnaCut steels over the past year, I can confidently state that MagnaCut has become my go-to choice knife steel.
This is particularly due to its incredible balance of properties, particularly its exceptional toughness and edge retention.
While SPY27 is a Spyderco-exclusive steel that improves upon the grindability and ease of sharpening of S30V, MagnaCut betters these qualities
I would however, suggest picking MagnaCut knives from only reputable knifemakers, not every knife maker has mastered the heat treatment of MagnaCut for optimal properties.
If you’re specifically seeking a Spyderco knife, SPY27 remains an excellent choice, especially if you prioritize the renowned quality and attention to detail that Spyderco is known for in their knives.