D2 vs. M2 vs. A2

mathman

mathman

Joined
Jul 1, 2005
Messages
186
OK, I searched and I can't find the info comparing these three...what can you tell me. I know that these aren't stainless steels (right?) and it seems that they are all fairly popular.

I'm considering getting a BM 710 with the M2 blade and this is (primarily) why I am asking.

Thanks.
 
I believe they are considered semi-stainless steels. I remember someone saying that D2 has better corrosion resistance than M2. I haven't even heard of A2, what knives have that?
 
All Chris Reeve Fixed blades, Bark River, Some BJ, many use A2. from what I have seen using it it must be semi stainless, holds a good edge and takes a good edge. If Chris Reeve thinks it's the best for his fixed blades there must be something to it :)
 
D2 has quite a bit more chromium than D2 or A2. This makes it much more corrosion resistant than the other two, but it's still not quite what the industry considers "stainless". You'll often see it called "semi-stainless".

M2 is a high-speed tool steel. Stuff like drill bits and lathe tools are often M2. It's a high-hardness, long wearing stel.

A2 is also a tool steel, but you're more likely to see it used on things that take stress or impacts.

Somebody with more knowledge in metalurgy could explain things better than I.

If I were to have a knife for chopping or prying, give me A2.

For a knife for slicing/cutting, M2 would get the nod.

In most cases though, either will get the job done and you'd probably not notice the difference. Unless every day you're out in the bush chopping branches and splitting firewood. But for a pocket knife, don't worry about it. I don't know of any company offhand that gives a choice between M2 and A2 anyway.

I have knives in both M2 (BM710HS) and A2 (Severtech). My Severtech is easier to sharpen, but the M2 holds an edge a bit longer. But the M2 is 60-62Rc, and the A2 is 59-60, so this observation is more likely due to the heat treat/hardness rather than the properties of the alloy itself.

A more appropriate comparison would be between M2 and D2, since Benchmade uses both (and you're looking at the 710HS). Again, the D2 will be more resistant to rust/staining. However, D2 is notoriously difficult (time consuming) to sharpen. The M2 will sharpen up a bit easier, but be easier to stain. M2 is easier to get a polished edge on, D2 has a rather large carbide matrix, so it'll be rougher/toothier. To be honest, I can't really say which holds an edge better, since both do it so well. I'd give the nod to M2 if only because I prefer the polished edge. I can get a pretty fine edge on D2, but with use (especially cardboard) it gets toothy on its own. Depending on your preference, you might like that, you might not.

BTW, Chris Reeve uses A2 in some of his fixed blades.
 
D2 has 12% chrome, and A2 has 5% chrome. I don’t remember how much chrome M2 contains, but it rusts very easily.

I have a couple of CRK one-piece fixed blades. Chris Reeves A2 holds a very good edge, and it is easy to sharpen.

D2 takes and holds a very good edge, but can be hard work to sharpen. D2 can be brittle, but I’ve never noticed this in the small (less than 5”) blades that I have owned/used. If the heat treatment is right brittleness doesn’t seem to be a problem.

I personally don’t understand why Benchmade use M2 instead of D2 in some models. D2’s edge holding and semi stainless characteristics make it a pleasure to own and use.
 
Wow, that's some great information...thanks a lot!

I'm probably going to go with the M2 BM 710 as it seems like this steel is very good...just have to make sure I take care of it in terms of corrosion.
 
Since there is no 710 in A2 and there was no folder in A2 for comparision, what was your question aiming for?
 
mathman said:
Wow, that's some great information...thanks a lot!

I'm probably going to go with the M2 BM 710 as it seems like this steel is very good...just have to make sure I take care of it in terms of corrosion.
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You don't really have to do much. The coating takes care of most of the blade, all that is exposed is the edge. Any time you use it on something wet, wipe it off with a napkin or something (I usually just wipe it on my jeans). If you cut something that might be sticky or caustic/acidic (like an apple), rinse it off with water and dry it. A bit of mineral oil or a rubdown with a Tuf-Cloth is a good idea too. The pivot area is exposed too, where the blade hits the AXIS lock, but since this area is going to be lubed (or should be, anyway), it'll stay rust free unless you dunk it in water or something. For the lock and pivot, canned air and Militec are your friends.
 
NGK-Webmaster said:
All Chris Reeve Fixed blades, Bark River, Some BJ, many use A2. from what I have seen using it it must be semi stainless, holds a good edge and takes a good edge. If Chris Reeve thinks it's the best for his fixed blades there must be something to it :)
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John Greco also uses A2 and it holds an edge quite well.
 
djolney said:
I personally don’t understand why Benchmade use M2 instead of D2 in some models.
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It is tougher, harder and more wear resistant - aside from corrosion resistance, it is pretty much directly superior.

-Cliff
 
mathman said:
OK, I searched and I can't find the info comparing these three...what can you tell me. I know that these aren't stainless steels (right?) and it seems that they are all fairly popular.

I'm considering getting a BM 710 with the M2 blade and this is (primarily) why I am asking.

Thanks.
Click to expand...

Here is some info on various steels FYI:

http://users.ameritech.net/knives/steels.htm

http://www.ajh-knives.com/metals.html

http://spyderco.com/edge-u-cation/index.php?item=3

http://www.nakededgecutlery.com/knifesteels.htm

Does this help?
 
A2 is a very tough (high impact toughness) steel. Quite a bit tougher than pretty much any real stainless steel. According to the technical data about half way between the average premium stainless (like S30V or ATS-34) and the shock steels like S7 or S5. Edge retention is also about half way between those two, but the stainless steels taking the cake this time. Not as wear resistant as D2 or M2 All in all a nice trade-off. And in my experience take a wonderful edge, very easy to sharpen. However, I wouldn't even call it semi stainless. It's not terrible if you take care of it, but unoiled in the sink it will get pretty ugly pretty quickly (minutes). AFIK it contains only little more Cr than 52100.

M2 toughness (correct me if I am wrong, Cliff) is tougher than your average premium stainless, including D2 but not by all that much. Not as tough as A2 or other HC steels. The use as a bladesteel surprises me, despite its good characteristics, as it is optimized as a high speed steel (meaning it won't lose its temper at elevated temperatures), which isn't really a requirement for a knife I would think. But I guess there is no point in arguing with success. I believe it is a much more fine grained steel than D2 and should potentially a much better edge than D2. Should be about as wear resistant as D2.

Boy I wish they would use M2 in the AFCK instead of the 710. I would be sold immediately.
 
Yeah, I have a BM 910 HHS in M2 and the stuff has finer carbides and I can sharpen it at a much shallower angle than D2 (for the sake of experiment, I reprofiled it using the little disk they use for a thumb stud as a guide... near as I can tell, this is about 7 degrees per side) and the thing came out like a razor (haven't abused it other than cutting cardboard or whittling on soft pine, but the edge held up with no chips).

Trying to get D2 to such a shallow angle causes the carbides on the edge to fall out so it is like a micro saw... The larger carbides means it likes a wider angle and will take a smooth polished razor edge at 15-20 degrees per side. It is more wear resistant than most all stainless steels I've tried (BG-42 comes close)

Basically M2 is a bit more wear resistant and will tollerate much finer edges than D2, but is more prone to rust (gave it a wipe with mineral oil last yer and haven't had a speck of rust, but I would keep it oiled or waxed and keep it dry as possible)

People say that both D2 and M2 are hard to sharpen, but I have had no problems at all with either of them. They reprofile quckly on a coarse DMT or Eze-Lap and polish up just fine on Shapton, King and MinoSharp waterstones (they are a bit hard and very wear resistant so it would be a chore to sharpen them on natural water stones and your arm would probably fall off if you tried to sharpen them on Arkansass stones, so stick with the silicon carbide or aluminum oxide water or oil stones). I haven't tried A2
 
Although I do plan to get a knife in M2 some day, I just ordered a BM 710 in 154CM...I don't want to worry about corrosion since this knife will undoubtedly be used to cut fruits and veggies, etc...you know, limes for Coronas and things like that :D ...thanks again for the info guys.
 
mathman said:
Although I do plan to get a knife in M2 some day, I just ordered a BM 710 in 154CM...I don't want to worry about corrosion since this knife will undoubtedly be used to cut fruits and veggies, etc...you know, limes for Coronas and things like that :D ...thanks again for the info guys.
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What about buying a cheap kitchen knife with a carbon blade and see and learn what importance rust resistance really does mean to you?

Are you deciding by "heard about" and "believe so"?

But it is your money, not mine.
 
154CM will still rust up if you don't take care of it. Citrus is especially caustic to steel. If you cut a lime with your 154CM 710 and don't clean it, you'll have rust spots in the morning. Rinsing with water, then toweling it off should do the trick, although you might want to go further and coat it with mineral oil or a Tuf CLoth.
 
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