CPM MagnaCut – The Next Breakthrough in Knife Steel

[Joshua J.]

Haven't followed this steel too much, so I've only been looking at some different charts, etc. Is everyone excited for this steel because it's a great all around steel? So has above average toughness, good edge retention and great corrosion resistance? I'm trying to think of the type of knives it would really excel in use. I have a lot of folders in M390/C20V. I've never chipped or damaged those edges, but the Magnacut may excel at being a tougher use knife? Corrosion resistance seems about the same. Edge retention seems a little lower, closer to S35V and Elmax.

Years ago I came to the conclusion that virtually all of my blades dull by destructive contact before they ever have the chance to wear down by abrasion.
Magna Cut focusing more on durability means for the average user those blades should last a lot longer than blades that are likely to chip out on hard contact.
Abrasion resistance is all fine and dandy, but it needs to be paired with adequate durability.

If it's a kitchen knife then it will always dull by impact with the cutting board and embedded particles.
For EDC that usually means cardboard and hard plastic. Cardboard is often dirty and sometimes has staples, I know staples in boxes may not be horribly common but you only need to "accidentally find one" a few times a year to consistently kill your best sharpening jobs.
In my opinion extreme abrasion resistance is practically only useful in factory machines where you absolutely know that nothing other than the intended cutting medium will ever touch the blade.
(Not that it's going to stop me from buying a Blurple Mili)

 

[POCEH KOCEB]

That’s a Salt 2 with H1 blade. You can see the larger “H1” logo on the blade.

My bad, I think you're right...

 

[353]

Holy cow, I didn’t look closely enough to see the Native Salt will be in MagnaCut! I’ll definitely need one of those.

Yes, nice move from Spyderco. And they obviously have faith in the steel beeing as(or close to) good as LC200N regarding corrosion resistance.

Anyone knows when they drop?

 

[Joshua J.]

Continuing my train of thought from above, it's easy for people to underestimate the importance of durability in relation to edge retention because testing is usually standardized for edge angle, but when you understand that a blade sharpened at 20 degrees will hold an edge twice as long as one sharpened at 30 degrees: https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
It makes sense that you're going to get better edge retention, and ease of sharpening, and better cutting ability overall, by using thinner geometry with a more durable steel vs. just trying to brute force abrasion resistance at a more obtuse edge angle where brittle steel types will be less prone to damage.

So for example CPM 4V (the expected equivalent of MagnaCut) at 20 degrees will hold an edge longer than Rex 121 at 30 degrees, but Rex 121 is an order of magnitude less durable.
So with each steel type optimized for the thinnest possible edge without taking damage on a given cutting medium my bet is Rex 121 would (almost) never perform better than 4V (excluding edge cases where the cutting medium is extremely gentle and you face near zero penalty for low durability).

 

[jstn]

Continuing my train of thought from above, it's easy for people to underestimate the importance of durability in relation to edge retention because testing is usually standardized for edge angle, but when you understand that a blade sharpened at 20 degrees will hold an edge twice as long as one sharpened at 30 degrees: https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
It makes sense that you're going to get better edge retention, and ease of sharpening, and better cutting ability overall, by using thinner geometry with a more durable steel vs. just trying to brute force abrasion resistance at a more obtuse edge angle where brittle steel types will be less prone to damage.

So for example CPM 4V (the expected equivalent of MagnaCut) at 20 degrees will hold an edge longer than Rex 121 at 30 degrees, but Rex 121 is an order of magnitude less durable.
So with each steel type optimized for the thinnest possible edge without taking damage on a given cutting medium my bet is Rex 121 would (almost) never perform better than 4V (excluding edge cases where the cutting medium is extremely gentle and you face near zero penalty for low durability).

True, and while steels like LC200N, AEB-L, and 14c28n don’t have great edge retention on paper, if they can support a thinner edge they do have great retention. The great thing about MagnaCut is it has very good retention on paper AND can be taken thinner. When you throw in the corrosion resistance I don’t think it can get much better IMO. Unless Larrin invents adamantium; I wouldn’t put it last him.

 

[Twindog]

Continuing my train of thought from above, it's easy for people to underestimate the importance of durability in relation to edge retention because testing is usually standardized for edge angle, but when you understand that a blade sharpened at 20 degrees will hold an edge twice as long as one sharpened at 30 degrees: https://knifesteelnerds.com/2020/05/01/testing-the-edge-retention-of-48-knife-steels/
It makes sense that you're going to get better edge retention, and ease of sharpening, and better cutting ability overall, by using thinner geometry with a more durable steel vs. just trying to brute force abrasion resistance at a more obtuse edge angle where brittle steel types will be less prone to damage.

So for example CPM 4V (the expected equivalent of MagnaCut) at 20 degrees will hold an edge longer than Rex 121 at 30 degrees, but Rex 121 is an order of magnitude less durable.
So with each steel type optimized for the thinnest possible edge without taking damage on a given cutting medium my bet is Rex 121 would (almost) never perform better than 4V (excluding edge cases where the cutting medium is extremely gentle and you face near zero penalty for low durability).

Thanks for the thoughtful post. I see your point, but I suspect the issue is more complicated. For one, the data on a 10 dps edge cutting twice as long as a 15 dps edge was determined by testing just one steel. Ten dps is pretty acute, and it's going to have trouble with any hard use, regardless of the steel. Any Rex 121 knife is going to be a special-use knife.

I have a Rex 121 knife from Bluntcut that I use exclusively for cardboard. The blade stock is about 0.07 inches a the spine just past the plunge line, with a full distal taper. The edge width is 0.005 inches at the shoulders (BTE). The edge angle is 15 dps. I doubt that any 10 dps edge with a more normal, but still acute BTE width of 0.015 inches would outperform it in pure cutting.

It can hold that thin edge because it is extremely strong -- 70 Rc. Toughness without that kind of strength will roll or dent easily at that thinness.

My Rex 121 cardboard knife is a joy to use because it cuts effortlessly. It never needs sharpening. A 4V knife would be much tougher and much better for normal knife usage, but I doubt you could ever get it to output my Rex 121 cardboard knife.

 

[Chronovore]

True, and while steels like LC200N, AEB-L, and 14c28n don’t have great edge retention on paper, if they can support a thinner edge they do have great retention. The great thing about MagnaCut is it has very good retention on paper AND can be taken thinner. When you throw in the corrosion resistance I don’t think it can get much better IMO. Unless Larrin invents adamantium; I wouldn’t put it last him.

This is a good point. I've noticed that both 14C28N and 12C27 punch above their grade. The usual answers for why include grain structure, clean composition, and toughness that supports a thinner edge.

I don't know about Adamantium but I'm still searching for the lost recipe to Orichalcum.

 

[Joshua J.]

Thanks for the thoughtful post. I see your point, but I suspect the issue is more complicated. For one, the data on a 10 dps edge cutting twice as long as a 15 dps edge was determined by testing just one steel. Ten dps is pretty acute, and it's going to have trouble with any hard use, regardless of the steel. Any Rex 121 knife is going to be a special-use knife.

I have a Rex 121 knife from Bluntcut that I use exclusively for cardboard. The blade stock is about 0.07 inches a the spine just past the plunge line, with a full distal taper. The edge width is 0.005 inches at the shoulders (BTE). The edge angle is 15 dps. I doubt that any 10 dps edge with a more normal, but still acute BTE width of 0.015 inches would outperform it in pure cutting.

It can hold that thin edge because it is extremely strong -- 70 Rc. Toughness without that kind of strength will roll or dent easily at that thinness.

My Rex 121 cardboard knife is a joy to use because it cuts effortlessly. It never needs sharpening. A 4V knife would be much tougher and much better for normal knife usage, but I doubt you could ever get it to output my Rex 121 cardboard knife.

Rex 121 with that geometry and hardness is going to be a legendary blade, but I think REX 121 at 70RC is trying to answer a very different question from the question MagnaCut is trying to answer.

This is the ultimate dedicated cardboard knife, but as you said it is a special use steel, how would that alloy and geometry configuration be received in a folding knife sold to thousands of people on the open market? For the average user the idea of this type of cutting performance is pure fantasy because Rex 121 optimized for cutting will never survive an EDC environment.

Whether or not Spyderco or other companies would ever consider selling a knife sharpened at 10 DPS is of course another discussion entirely (factory setup etc.), but at least there's room to have the discussion now. If it is possible to demonstrate that an average user doesn't automatically destroy MagnaCut at 10 DPS then you open the door to showing people a new world of knife performance.

 

[353]

Some great cutting test results from our man down under, factory edge, on two specimens.

He'll prob post his 17° per side, mirror edge testing next week. But very impressive results from factory!

 

[jstn]

Some great cutting test results from our man down under, factory edge, on two specimens.

He'll prob post his 17° per side, mirror edge testing next week. But very impressive results from factory!

I have three blades in it I've been almost exclusively using lately. Most things don't live up to the hype, but MagnaCut really seems to. Really great edge retention, and I've done some chopping and batoning with mine with absolutely no damage. I haven't been able to get it to rust either with water and sweat. I don't do anything extreme with my knives so others' results may very, but for my needs, it is certainly exceptional. I've ordered two more knives in it and can't wait to get some folders.

 

[Joshua J.]

I have to wonder what edge angle Spyderco used.
If they did deviate from the usual 20dps angle on the final edge then it would significantly impact the testing, and that's basically the only way I can see these factory edge results reaching the conclusion they did.
Normally the 17dps tests are an improvement over the factory edge, but for that to be the case here MagnaCut would beat K390 and S110V at the same edge angle, and I just can't see that being a possibility.

 

[nattynarwhal]

I have to wonder what edge angle Spyderco used.
If they did deviate from the usual 20dps angle on the final edge then it would significantly impact the testing, and that's basically the only way I can see these factory edge results reaching the conclusion they did.
Normally the 17dps tests are an improvement over the factory edge, but for that to be the case here MagnaCut would beat K390 and S110V at the same edge angle, and I just can't see that being a possibility.

I think magnacut is definitely punching above it’s weight here. At the end of the day, you’re talking about a steel with a carbide volume far lower than s110v and k390.

Still, this steel should have s35vn like edge retention (at 63 hrc) and be as tough as 4v, while being as corrosion resistant as Lc200n. That’s an incredible mix of properties, and should be enough to sell steel geeks on it as a balanced steel. Just don’t expect it to outperform the steels designed with wear resistance as a priority.

 

[Gtscotty]

I took my MC mule down to about 12 fps, and let a friend use it to breast out a duck. I did notice a little chipping on the edge where he sliced down against the breast plate, but it seemed very small and minor. I need to find some hard work for it, but I'm pretty excited about picking up some MC in a few folders.

I've pre-ordered the Native 5, and now that I know the polymer handled Hogue Deka is going to be shipping with MC blades soon, I'll probably have to pick up one of those as well (maybe instead?). The listed hardness on Hogue's website was a little bit of a let down at 60-62 HRC. That would normally be good, but when I look at Larrin's MC testing, it really seems like it would shine in a small blade closer to 63-64 HRC.

 

[toker]

I took my MC mule down to about 12 fps, and let a friend use it to breast out a duck. I did notice a little chipping on the edge where he sliced down against the breast plate, but it seemed very small and minor. I need to find some hard work for it, but I'm pretty excited about picking up some MC in a few folders.

That angle seems much too thin, especially if it's chipping from a single bird. I have a Busse in Elmax (17 degree angles) that I used to breast out dozens of birds in multi-day waterfowl trips and the blade was still razor sharp.

 

[Gtscotty]

That angle seems much too thin, especially if it's chipping from a single bird. I have a Busse in Elmax (17 degree angles) that I used to breast out dozens of birds in multi-day waterfowl trips and the blade was still razor sharp.

Well the point of going with a more acute angle than usual was to get an idea of how a relatively tough stainless steel does at higher performance geometries. I don't know about much too thin, I want to put it though some more use to see how it responds, I wasn't really paying attention to see if he might have hit some shot or cut against the boat deck or something. The whole reason I got the mule was to play around and experiment, I can always change the angle around if I get the inkling.

 

[toker]

Well the point of going with a more acute angle than usual was to get an idea of how a relatively tough stainless steel does at higher performance geometries. I don't know about much too thin, I want to put it though some more use to see how it responds, I wasn't really paying attention to see if he might have hit some shot or cut against the boat deck or something. The whole reason I got the mule was to play around and experiment, I can always change the angle around if I get the inkling.

Sorry. I didn't mean my post to sound negative. I understand that you're doing it for testing.

 

[Gtscotty]

Sorry. I didn't mean my post to sound negative. I understand that you're doing it for testing.

Nothing to be sorry about, it is a thin grind, and testing is probably a strong word for anything I do knife related, mostly I'm just playing around with it, lol.

 

[toker]

Nothing to be sorry about, it is a thin grind, and testing is probably a strong word for anything I do knife related, mostly I'm just playing around with it, lol.

I'm impatiently waiting for Halpern to get some scales back in stock. I'm also eager to put the Magnacut Mule to the test in the kitchen and in the field. I'm going to give the factory edge a try and then go thinner from there. I think a lot of people go for 17°, so I'm curious on how that will perform.

 

[Currawong]

I've been whacking away at saplings and woody weeds around the farm with some fairly thin-ground magnacut, and hit rocks and dirt a few times. It does chip, but the chips are very small ones, almost too small to see. So it's holding up pretty well to abusive use from my experience so far.

 

[353]

but I'm pretty excited about picking up some MC in a few folders.

MC will be a pretty cool abbrevation for this steel.