School me in cpm m4

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Omega Leather Works

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Jun 13, 2007
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Hey guys, I'm really wanting to know more about this steel.

What is it good at, bad at, what kind of knives (and uses) is it best suited for? That kind of thing.

Thanks.
 
It's probably one the best premium carbon steels.

It's hard to profile but easy to sharpen, and gets so sharp so easily its truly scary.

Seems to work equally well with small and large blades.

Can be honed to very thin angles.

Tough as a pry bar.



What knife where you looking at with this steel?
 
Edge retention is above S30V/D2/CPM154, just below M390, toughness is above all those but below 3V or 5160, it's not stainless though, so you do have to clean it off if you use it in salt water or in acidic foods, but it's not as bad as 10XX or 52100, A2, etc.
 
I believe M-4 is tougher at higher hardness than ZDP-189 is. If they were both HT to same hardness I think M-4 can still be considered "tough" and still very high on the RC hardness chart, whereas 189 is has lost a little bit of its toughness at its upper limits of hardness.
 
Yeah, compare it to different steels. That helps. I have a little experience with m390, none with 3v (sadly) and plenty with s30v as well as "regular" steels.

As far as the knife I'm interested in... I'm not. Yet. I want to have a custom made this year but I haven't put together what materials or even intended usage yet. Just kinda trying to piece together things in my mind. I have a Contego in m4, but haven't really used it. It's been customized so I figured I'd keep it pristine, but I've changed my mind. I'm going to beat the hell out of it instead, I just need to figure out what to cut! :D

Btw, thanks niner! Helpful as always. :thumbup:
 
PatrickKnight- I never thought of it that way... CPM M-4 is a love child of 3V and M390!
 
M4 is a solid steel and while I do like it I think that other steels are better for specific designs. M4 is really a nice jack of all trades steel that is high on edge retention. The problem is how to implement it in a knife where the qualities of M4 are superior to other steels. For example for folders I prefer stainless so I'd go with something like M390 or S90V (not to mention both have better edge retention). In a small knife I prefer to use M390 or ELMAX for stainless and high hardness 3V for carbon. In a small blade toughness isn't a huge concern and I think edge retention and stain resistance are more important than really high toughness. But when I do want a ton of toughness in a small blade in high hardness 3V is superior to M4 by a large margin in toughness while only being slightly behind M4 in edge retention. For bigger blades I think 3V far superior to M4. 3V can take a thinner edge, chips less, is tougher in terms of impact strength and is also more stain resistant than M4.

Everyone has their own opinion and while I think M4 is great, (my EDC is an M4 BM Contego) I won't be using it any time soon because after alot of use and experimentation I think there are better steels out there for task specific designs. Not to mention M4 is a PAIN to grind, polish, and compared to something like ELMAX with similar edge retention its a pain to sharpen as well.
 
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So much depends on the hardness and geometry of the blade that generalizations often won't apply to the steel in individual knives. I like 3V for large choppers -- and I use a 3V bolo quite often. It holds up great. But I had a bowie in 3V that was plenty tough, but in very hard use I bent the last inch of the blade. A 1095 knife passed the same test without problem.

My first Benchmade AFCK M4 was relatively soft (59 HRc) and didn't hold an edge especially well, so I had it rehardened to 64 HRc. The blade shattered into three pieces with just lateral hand pressure. On the other hand, I chopped into some firewood with a Gillson M4 camp knife hardened to HRc 64-65 and it held up extremely well -- but it had an amazing convex edge on it. It showed no damage while the bowie in 3V had very slight denting. I don't know the hardness of the 3V, but the hardness, heat treat and edge geometry play such huge roles that the individual qualities of the steel can often be lost in a rounding error.
 
Are competition choppers still making their knives out of m4 or have they moved on to something else? Afaik they are all m4. If other steels fit the role better why use it?
 
M4 is far better at edge holding than both 3V and Elmax from my experience.

I have test Spyderco Tuff, Fehrman Cold Fury, ZT0561 and Spyderco Galye Bradley to cut many stuff like cardboard, metal sheet and also some synthetic rubber which very tough. I would say M4 hold the best edge by far better than 3V and Elmax which both has worse edge holding than Paramilitary2 S30V...
 
IMO CPM M4 provides the best combination of toughness and wear resistance. It is capable of maintaining a decently tough edge at harnesses upwards of 65 Rc. One aspect of toughness that is not discussed often enough is that you can afford to go thinner with tougher materials, so if the M4 is tougher you can have a thinner blade, and more importantly a thinner edge angle. combine this with the excellent wear resistance and high hardness, and you have a wicked slicer. As others have mentioned it sharpens pretty easily, and really gets that razor sharpness fairly easily. Also though it is not stainless by a long shot, it is not going to corrode into powder either.
 
CPM-M4 definitely the best performer steel available IMO. The only negative thing about M4 is it rust just easily as carbon steel like 52100 or O1. I live in tropical zone though.
 
Okay I wasn't aware that you could take the edge to an acute angle. So regarding my 810 (call it 63 rockwell hardness) what is a reasonable max inclusive primary edge for cutting average material?
 
this is by far my favorite steel. in my very unscientific usage it has held a working edge longer than s30v by a noticeable margin, while being very tough.

it is also very stain resistant compared to traditional carbon steels, you really have to try to get it to patina. My main Edc has been a spyderco military in this steel. I commuted by bicycle for about a year and a half while carrying this clipped inside my waist band. It has been through torrential downpours, then left in a pile of soggy clothes all night when I got home. it has been on me for 100 degree bike rides, followed by 8 hours of manual labor, sweating the whole time. it has seen everything in between, and never had more than a light peppering of rust or patina. and I do not oil it, other than the pivot from time to time.

I have also never had to use more than the sharpmaker brown stones to stay honed. it is very easy to keep honed and sharp, though they say it is hard to profile. I have never had to profile it, though.

If you are an edge holding snob, there are better. if you are a toughness snob there are better. If you are scared of staining there are better, but IMO it does everything very well.

I would feel fine trapped in the wilderness with it, or out on the ocean, or anything between.
 
Strigamort said:
Okay I wasn't aware that you could take the edge to an acute angle. So regarding my 810 (call it 63 rockwell hardness) what is a reasonable max inclusive primary edge for cutting average material?
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Average material? That's purely subjective, what's average for you?

I set the bevel on my 950-1201 to 20 degrees inclusive and micro beveled at 30 degrees for my EDC tasks, cardboard/banding etc. no edge damage, could probably go thinner.

Started work on the flats with intent to polish it, took a minute of sawing into my 400 grit stone before it stopped cutting printer paper... At that moment I fell in love with that steel.

It simply blows 154cm out of the water, s30v... a joke, best steel I've sharpened... With no prying in your EDC, you
Can probably leave it at 20 degrees inclusive and suffer no blade damage.
 
Strigamort said:
Are competition choppers still making their knives out of m4 or have they moved on to something else? Afaik they are all m4. If other steels fit the role better why use it?
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I wouldn't say "all" but a large percentage are indeed using CPM-M4 with great success. But it's important to remember that cutting comps are highly-controlled situations; those folks don't have to worry about knots and dirt and grit, and they're definitely not doing anything resembling prying - so extreme toughness* is not that big of a factor. CPM-M4's ability to hold a very fine edge at high-hardness is what makes it a winner in that situation, and probably an excellent choice for any pure cutting application.

* according to both published reports and anecdotal evidence, CPM-M4 is certainly not a weak or "non-tough" steel. It exceeds the toughness of good steels like CPM-154, D2 and others in that range, and approaches A2 levels. It is fine-grained and tough enough to support very thin edges, as noted above. It's expensive and not corrosion-resistant, and I wouldn't choose it for a real beater/sharpened prybar/combat knife, but for pretty much anything else it should perform very well indeed.
 
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