M2 - over hyped?

Peter Ervin · Jul 30, 2000

I have a couple of knives with the M2 tool steel and have served me fine. They hold an edge and I've had no complaints. I was led to believe that M2 was superior in the toughness stakes and without really abusing my knives I took their word for it.
I was looking through the August edition of Blade and on page 139 Wayne Goddard has an article on steels and their properties. I was amazed to read that M2 is quite low on toughness compared to A2 and D2. Mr Goddard's chart stated that in regards to toughness M2=40, A2=80 and D2=64. He also states that M2's toughness is only fair.
Now, I believe Mr Goddard, he is alot more of an expert on steels than I'll ever be and his experience with most of the steels far surpasses mine. I am always dubious about advertising and marketing ploys and this maybe another example of don't always believe what you read. M2 was originally promoted as being tougher than ATS34 and 154CM and most people aren't going to abuse their knives to find out whether this is true or not.
How has M2 stood up in your knives?

Peter

SALTY · Jul 30, 2000

I can tell you from experience that A2 is tough stuff. I too have an M2 from Benchmade, but wonder if Benchmade is into marketing hype.

Knife Outlet · Jul 30, 2000

Peter, maybe you should review what toughness is. In the knife business it relates to the ability of the knife blade to accept stress from different directions. Tougher generally means softer. There is no doubt that M2 is tougher than ATS-34 since ATS-34 is not very tough at all. It is actually on the brittle side. Generally, you give up edge retention when you gain toughness and vice versa. Now whether it is tougher or less tough than other tool steels such as D2 is something I'll leave up to experts like Mr. Goddard. Comparing a tool steel to a stainless or quasi stainless steel isn't really very meaningful. Don't get concerned. So far nothing you've read would seen contradictory to me. It's a matter, I think, of understanding the terminology. I think ATS-34 appeals for good reasons to some folks and tool steels appeal to others for good reasons as well. Take care.

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Fred
Knife Outlet
http://www.knifeoutlet.com

rdangerer · Jul 31, 2000

I've been trying to sort out whether D2 is tougher or more brittle than M2 at a given hardness myself, so your question of M2 vs. ATS-34 is of interest to me as well.

I consider ATS-34 and 154CM so very close in metallurgy that I call them equivalent for this discussion.

Benchmade is one of the least hype-ridden companies I know of, for starters. And my Benchmade's are of good quality and the ATS-34 appears to have a very good heat treat compared with other ATS-34 blades I own. So far, my experience with Benchmade's heat treating process is good. Other's experiences may vary.

I also read Goddard's article, it's a good overview (but too short!) from a very hands-on guy.

Wayne's experiences seem to be at odds from what I can find in the reference literature I happen to own at this time. Both show A2 to be roughly twice as tough as D2, M2, and ATS-34. Wayne does use a source of D2 that differs from many others....he uses OK-6 Planer blades from Ohio Knife Company, and his D2 has 0.38% extra carbon, 0.26% extra vanadium, and contains 0.02% tungsten and 0.105% nickel above and beyond normal D2. That extra nickel in particular may be what gives his D2 the extra toughness he seems to have noted.

Bob Dozier says A2 is a good bit tougher than his favorite D2. There's another data point... Dozier ain't no hype-ster either.

Now, the hard part is understanding what Rockwell hardness levels were used for the Charpy C-Notch impact tests for toughness. Here's what I have:

A2 @ HRC 60 = 40 ft-lbs Charpy C
D2 @ HRC 60 = 20 ft-lbs Charpy C
M2 @ HRC 62 = 20 ft-lbs Charpy C
440C @ HRC 56 = 20 ft-lbs Charpy C
CPM 420V @ HRC 56 = 20 ft-lbs Charpy C
CPM 3V @ HRC 60 = 60 ft-lbs Charpy C

I don't have charpy values for 154CM=ATS-34, but it is simply graphed in another section of my Crucible book to be slightly higher (maybe 20%?) than 420V and 440C, so based on a (risky) estimate, I'd say 154CM might be around 24 ft-lbs at HRC 60.

Note one problem here: M2 is given an equal toughness rating to the steels above but it was tested at HRC=62. And hardness and toughness are inversely related for most steels for the most part (some have weird peaks in the curves, but I digress). So M2 at RC60 should be as tough or tougher than ATS-34.

Benchmade heat treats their M2 to HRC 60-62, the 2 point spread reflecting variance in the heat treating and across the blades due to thickness, etc. Benchmade similarly treats ATS-34 to HRC 59-61. So midrange, there is 1 point difference between Benchmade's ATS-34 and M2.

In very general terms, higher hardness means better edge retention. So with M2 being a slightly "tougher" steel, they can heat treat it about 1 RC point higher and not suffer additional brittleness.

So, summary for toughness: ATS-34/154CM and M2 are not very far apart, at least according to the two sources I have, one being Crucible's Steel & Alloy Selector, the other being a book on heat treating by Bill Bryson. I can also draw this conclusion: A2 is about twice as tough as either 154CM or M2.

If you really want to dodge science, and do this in the real world, buy an AFCK of ATS-34 and another of M2, and cut something harsh like bundles of wire or very uniformly sandy rope, or use them to chop hard wood (not the domain of a folder). See which one chips out soonest.
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Wear resistance:

Goddard shows ATS-34 and D2 in a dead heat at HRC 60.
One of my sources shows D2 and M2 in a dead heat as far as wear resistance, the other shows M2 to be about 50% better but that was at M2 @ RC62 and D2 @ RC60. (but still, M2 is well below CPM 420V for example, by a factor of between 1.5 and 3 these particular tests...)

One problem: my sources test wear resistance by a method that utilizes two cylinders of the metal that are rotated against each other. This test gets to a metric characterizing friction or galling type wear. The less used tests that are probably more applicable for knife edge holding would be true abrasion resistance, where the metal was abraded by some high hardness grit, like sandpaper or tungsten carbide grit, etc.

Unfortunately, I have no data that is "abrasion resistance" related, so the "wear resistance" numbers are just a bit less directly related to knife edge holding that I'd hope for. The steels may show different characteristics when testing methods change, i.e. they may change their rank order.

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Without doing any testing of my own, which is risky at best, my sense is that M2 isn't enough better than ATS-34 or D2 to make we want to tolerate it's lack of corrosion resistance. That's why I haven't bought into the M2 "fever" and plunged into an M2 AFCK. CPM 3V? Yeah, it's enough better in toughness that it would be worthwhile to have as a blade depending on cost and intended application (for a folder, I don't think it fits the task, for a big chopper, it would be great, but so are INFI and VascoWear). At a similar level of toughness to D2, I'll take CPM420V any day due to it's wear resistance and better stain resistance.

I await Benchmade's adoption of CPM420V.

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rdangerer@home.com

[This message has been edited by rdangerer (edited 07-31-2000).]

[This message has been edited by rdangerer (edited 07-31-2000).]

Mike G · Jul 31, 2000

Keep in mind, M2 is what most end mills, counter bores, reamers,countersinks, taps,lathe tools, ect. are made of, and they must be tough, and be somewhat shock resistant. M42 has a higher cobalt content, and resists wear much better than M2, and is also used in making machine tools. I don't have my charts in front of me, so I don't have details as to RC hardness, or exact make up of the two, or the exact qualities of each.

Danbo · Jul 31, 2000

My experience with M2 is pretty much limited to the old Gerber bird and trout knives. Those babies held an edge almost forever! But, they were a bear to sharpen. From what I've read, M2 is designed to be very abrasion resistant. I dont think toughness is one of its major virtues. I have seen M2 listed by Goddard as one of the steels he uses for small utility knives that dont see much chopping/prying abuse. I dont recall seeing Benchmade advertising M2 as a tougher steel. Buy an M2 knife for what it is; a knife that stays sharper longer than ATS34.

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Danbo, soul brother of Rambo

Jul 31, 2000

Wonderful discussion, thankyou.
Re: M2 If industry makes professional drillbits out of it, you can bet it's tough and wear resistant. BUT: not every knife is heat-treated the optimum way.....

ATS-34: there are 3 (very) different ways to heat-treat it. One for optimum "stain-less",
one "el cheapo-quicko", one for optimum
toughness (then: less "stain-less").

My "Nimravus" and my "mini-AFCK" in M2 are
not easy to sharpen (which is a good sign for toughness), very sharp and quite edgeholding.

BTW: a digest of a digest of a digest of a
digest may be extensive but not necessarely up to date.
Happy sharpening

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D.T. UTZINGER

[This message has been edited by ZUT&ZUT (edited 07-31-2000).]

Joe Talmadge · Jul 31, 2000

Heh, a bunch of interesting results, all at adds with each other! Three quotes, from three different people...

I was amazed to read that M2 is quite low on toughness compared to A2 and D2

Whereas Crucible says their toughness is very close, and experience tends to make me believe it.

I don't have charpy values for 154CM=ATS-34, but it is simply graphed in
another section of my Crucible book to be slightly higher (maybe 20%?) than 420V and 440C

ATS-34, at anywhere near its normal hardness (59-61, say) is nowhere near as tough as 440C at its normal hardness (say, around 57-58 Rc), in my experience. But, of course, I've never tried to compare both steels at 57-58.

My "Nimravus" and my "mini-AFCK" in M2 are not easy to sharpen (which is a good sign for toughness)

Actually, being difficult to sharpen doesn't tell you anything directly about toughness. However, one thing that can cause difficulty in sharpening is the steel being very hard, and the harder you make a steel, the less tough it becomes, generally speaking. Of course, the fact that Benchmade leaves the edges so thick is another big factor in difficulty of sharpening. Why is it you think hard-to-sharpen steels are tough?

Joe

Samurai6 · Jul 31, 2000

M-2 in known in the machine tool industry as being a very wear resistant, very hard, brittle steel. That is because it is generally run almost fully hardened at 63 RcH.

Benchmade runs it a little softer than most applications for the steel, and at 60-61, it is a good, tough, steel that holds an edge in the same league as any production super steel like BG-42 or 440V. Addtionally, how the steel is tempered makes a great deal of difference in its performance.

The bottom line is, when a Benchmade ATS-34 blade tip would snap, an M-2 blade tip will just bend slightly. This usually means you aren't getting ideal wear characteristics, what the tool industry is after, but it sure means you are getting a better hard-use knife blade. The M-2 Benchmades are high performance stuff if extreme stain resistance isn't required. Of course, ATS-34 isn't that much better an alternative in that regard.

[This message has been edited by Steve Harvey (edited 07-31-2000).]

[This message has been edited by Steve Harvey (edited 07-31-2000).]

Peter Ervin · Jul 31, 2000

Thanks for the replies fellas, it's good to see we have such a wide range of experiences and views here on the forums. Very informative.

Pete

SALTY · Jul 31, 2000

Bottom line; What are you looking for in a knife blade? If stain resistance is your prioity, no problem, there are steels that can do that.

However, if reasonable care is in the cards and holding an edge for a long time is your goal, then is M2 or A2 your choice?

For me, I have a use for a Sport Utility Folder that can live with abuse, be OK with sporatic and lazy sharpenings and get healthy doses of oil as a rust preventative.

Is M2 what I need?

[This message has been edited by Nimrod (edited 07-31-2000).]

Samurai6 · Jul 31, 2000

Nimrod,

"For me, I have a use for a Sport Utility Folder that can live with abuse, be OK with sporatic and lazy sharpenings and get healthy doses of oil as a rust preventative.

Is M2 what I need?"

You sound like a simple carbon steel man to me.

Not many sport utility folders made out of 1000 series. Mark Boyer was making one at one time, don't know if he is still making those or not.

M-2 is a high wear-resistant steel, and you will have the best luck with it if you touch it up regularly. If it gets extremely dull, getting the edge back can be a chore. Same with ATS-34 if it is good and hard though. Other than that, don't know why M-2 wouldn't work just fine for you.

Aug 1, 2000

Worshipful Greatest of all Grandmasters, if I said "it's not easy to sharpen, which is a good sign for toughness", I meant exactly that. Please forgive me for inadvertedly annoying Your Exalted High Wisdom.
A hard and brittle steel is "easy" to sharpen (well if you do not try to do it with a soft stone), because there will be but a little bit of burr building up. A tough steel on the other hand produces much more burr which is very tenacious to get rid of.
Again, my deepest and humblest apology.
It won't happen anymore.
Happy sharpening

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D.T. UTZINGER

rdangerer · Aug 1, 2000

At the end of the day, I can't get excited about a carbon steel folding knife and can't see why I would want to skew my selection of steel for a folder to get a really tough blade in trade for lack of corrosion resistance. Folder's see pocket carry and much utility work, so stainless (at least D2) is really high on my personal priority list. Just MHO.

I just don't see using a folder in any kind of situation (except emergency) where I needed exceptional toughness, because if I have some degree of control over the task, I'd be using a fixed blade of a thicker grind for the task, made outta something tough.

After watching my @$$hole boss snap the tip off my little Buck 503 about 20 years ago, (I still have it, short little pecker all reground and ugly now) using it as a freakin' screw driver before I could holler "stop", and then not offering to replace the knife, I just can't bring myself to do much with a folder that would require an abnormally tough blade (yeah, using a folder as a screwdriver with little prudence get's filed under "stupid"). Even cutting wire isn't a big deal unless you chop and hack at it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Now, for the good news. Many of us have heard about / read about / used CPM3V and know it is designed to be very tough (like INFI and Vascowear) while holding a very good if not exceptional edge in slicing activities.

Crucible reps at Guild Show told me that they should have a new version of 3V out, maybe late this year, that will have a chrome content in the 12-13% range, and so much Vanadium still in the mix that there will be enough free chrome to make it more stainless than D2 while staying relatively tough. I.e., the design goal of the "new 3V" is to make it 3V-tough and stainless.

Now THAT sounds like a steel that I would want to have in a hard use, working folding knife, for sure. Stay Tuned.

Crucible is impressing me ... they have a "knife team" of support personnel including the likes of Ed Severson, and apparently are making enough money, making enough progress, in selling steel to custom and later production (cheers for Spyderco and Kershaw with 440V) that they can afford to have some good, focused support of the knife industry ... witness the fact that I talked with TWO of their knife team reps at the Guild Show. This is a good thing.

Support Crucible with your dollars folks...they've done as much for blade steels in the past few years as anyone. (and Talonite is NOT a new thing, it's a flavor of Stellite, which people have used for well past a decade).

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rdangerer@home.com