CPM-M4 and M390

[MachSchnell]

I'm really excited about the M390 PM2 (pre-ordered!) and really want to pick up one of the tan Manix2 M4's as well. I might do a handle swap with the blue Manix2 to have color matching workhorses. :p

These might be the end all for folders :eek: ....at least for me.
Might then thin out some of the collection and experiment more with fixed blades.

Anyone who has experience with these steels feel free to chime in!

[Niles]

I'm excited for the m390's as well.

I've got the m4 manix as well and love it. It's easy to sharpen and has been holding its edge well. It will rust or discolor easily though, so watch out. The only thing I don't like about the manix is the handle. Hard cutting gives me hot spots after a while. The steel overshadows this fact, but it is a bummer.

[Zenith]

Been using the M4 military for a month and a half without rotation in my EDC until I left site a week ago. Can't complain about it, what I did learn is that M4 likes a slightly courser edge. 600grit diamond paddle, strop a few times and it would cut and cut and cut. I do low angles with a micro bevel. These steels are high carbide steels (under correction), not everyone likes them, but they are good nun the less. I prefer low vanadium content of 0.2 %

[jackknifeh]

No M390 knives yet for me. I have two with M4 (Manix2 and GB). I really like the steel. Not knowing much about the science of steel I take recommendations and examples to heart. When I learned that CPM-M4 is used a lot in knive contests I felt like it would perform my EDC chores like cutting string, opening cookie boxes, even the occasional tree limbs that seem go grow overnight in my yard. LOTS of cardboard or LOTS of rope that I have used to test edge retention are the only things I've cut with M4 that dulled the edge. The same material also dulled S30V and ZDP-189. Other than that it just doesn't get dull fast enough to even notice.

I put some patina on both my blades to aid in corrosion control and use Tuf-Glide so I think I'm safe as far as corrosion under non-salt water environments.

Jack
PS: My testing is minimal compared to some who post here so listen to them more than me.

[DeathBySnooSnoo]

No M390 for me yet either....notice I said yet :D But I like M4 a lot. I find that in terms of a productions steel it is probably the best all round steel. Very good edge holding and tougher than the majority of other steels too. I use my GB all the time, it is probably my most carried knife.
I have not had any issues with M4 and rust. There are only 3 reasons that I can think of why any one would have an issue with it. Either they live in a very very humid environment, they have an acidic body chemistry and they sweat a lot, or they just don't do proper maintenance on their knives.
Keep it clean and dry, and you should have no issues, if you live somewhere humid or sweat like a beast, use tuf-glide or something similar and give the blade a nice coating once a month or so.

I've used my GB for all kinds of things, general light use stuff, to dealing with a ton of cardboard after my move, to opening bags of sand and top soil, used it to carve out a notch in a 4x4 piece of wood when it was cut wrong for a new fence at my mom's. So for all kinds of work M4 does a good job and never seems to need more than a light touch up.

[Niles]

My issues with discoloration on the M4 were completely my fault. I had it in my pocket, got sweaty, and didn't think to pull it out and dry it off in time. I don't mind really. It's a user and the discoloration is minimal, but I watch out for it now.

Live and learn...mess up and learn again.

[hunterseeker5]

The M4 mules were pretty **** hard (at least in my test sample of one) and performed extremely well. Its worth noting as people have said before that it has a bit of a toughness advantage over other steels, but does have the (wear resistance?) of something like S90v. I have no CATRA tests to back my results, but I guess I'll say that if your cutting something gritty that'll micro-chip your edge I'd prefer M4, or if you want a high carbide volume steel which seems to hold its sharp sharp, not working sharp, edge longer M4 at a high angle is a great way to go. All that said though I've not gotten a satisfactory edge on it, or any of the other high carbide volume steels for that matter, without a diamond abrasive. Its kinda hard to say why its better, but when you use it you can sort of feel it. I will say that given its performance in my experience I was very surprised at where it landed in Ankerson's testing.

All that said why hasn't someone gotten a sprint run of the Para2 done in M4 yet?

[Blerv]

Yea I don't have my own tests but M4 is tougher and M390 has more wear resistance. With how nice M4 is for sharpening (no exp with M390) and how resistant it is to chipping I wouldn't be torn either way.

Frankly zdp is my hero for the money because you can buy 3 Dragonflys for one Para2 M390 Bentobox exclusive.

Ps: no clue Hunter...but I want one :) .

[hunterseeker5]

Currently Bladeforums is having a malware issue, so I can't view Ankerson's results, but as I recall it was at least two tiers down from the M390, CTS20cp, etc tier which quite frankly I found very surprising. I'm not trying to discredit his results, nor am I saying they're the final word on the steel, but I guess pretty much everything on that list I have experience with landed about where I expected it to end up with the exception of M4. Perhaps my mule isn't representative of M4 as a whole, or his test sample isn't, or maybe my feeling for it is just plain wrong but bottom line that one left me scratching my head.

I'm really not trying to incite controversy, I appreciate everyone's input and testing, and I'm REALLY thankful to people like CTS and Ankerson for doing all this work and then publishing it, but if we don't discuss the results we've lost 90% of its usefulness. :) I guess based on chemistry alone I'm a bit surprised that M390 ended up at the top as well, but I have a sneaking suspicion that M390 has a bit more to it than just its chemistry which might be revealed under a microscope.

Bento Box Shop is price gouging on the para2 sprint no doubt, but its my favorite knife of all time and I love collecting it in different steels. Its a pain in my *** but in this case I'll just suck it up and cough up for it. Certainly if you look at the value and performance of a Para2 next to many of the *cough* more expensive tactical folders which are predominantly frame locks you get superior lock strength, ergonomics, a smoother action, and the ever critical spyderhole. I'll tolerate it.

I actually bought my better half two dragonflies, one in H1 and one in ZDP, as a bit of a gag because they're cheap and I wanted to make fun of her for being a smaller woman. She normally likes to emasculate me in front of her relatives by pulling out a MUCH larger and more vicious knife than I'm carrying. If I carry a Para2 she carries a Matriarch. If I carry a full millie she'll take that as an opportunity to pull out a khukri....... Anyway like an *** I bought her the two dragonflies and I find myself liking them more than she does to the point where I stole her ZDP one. :P At the end of the day you really don't need as large a knife as you feel like you want most of the time. I think I've successfully derailed this thread now so back OT.

[phillipsted]

Bento Box Shop is price gouging on the para2 sprint no doubt, but its my favorite knife of all time and I love collecting it in different steels. .

I don't know about price gouging. BBS is taking a substantial risk signing up for a full run of a dealer exclusive knife - He probably had to sink over $60K into the venture to get on Spyderco's production calendar (just a guess). Now he's got to sell all these knives to recoup his money and make a profit.

Sure - I'd like for all the Para2s to be under $100 bucks. But I think his price is in line with the other sprints and exclusives - and the Para2 is worth it at this price point.

TedP

[MachSchnell]

I don't know about price gouging. BBS is taking a substantial risk signing up for a full run of a dealer exclusive knife - He probably had to sink over $60K into the venture to get on Spyderco's production calendar (just a guess). Now he's got to sell all these knives to recoup his money and make a profit.

Sure - I'd like for all the Para2s to be under $100 bucks. But I think his price is in line with the other sprints and exclusives - and the Para2 is worth it at this price point.

TedP

Totally makes sense, 800 pieces at $179 = $143,200. Soo getting a dealer exclusive must require a huge down payment.... and hope that they sell.

[angusW]

I'm excited about the M390 Para 2 as well. It will certainly be a nice surprise in the new year.

I'm not sure if this is the normal way of dealer runs but I remember Jon from edc forum saying, regarding the edc Manix 2, that he had to sell X amount of knives which would go towards paying back Spyderco. Can't quite remember all the details but I don't think he payed up front.

[Blerv]

Hunter, I recall the edge difference is M4 is lacking some of the mean carbides of M390, S90v etc. Based on this while it's tough and can be treated quite hard it lacks some edge holding in the likes of those steels. Frankly if it beats s30v but is MUCH tougher i'm happy. It seems to take a mean edge too :)

I recall Sal saying once (don't quote me) something like, "toughness, edge holding, corrosion resistance, price...pick three."

[Cliff Stamp]

Hunter, I recall the edge difference is M4 is lacking some of the mean carbides of M390, S90v etc.

M4 is an extremely high carbide steel, even when it is under tempered by almost 10 HRC points it still matches M390 on a CATRA test, which is mainly a test of wear resistance. The biggest difference between the two for a user is one is stainless and one is not. Both of them are extremely brittle steels, with an impact toughness so low you can not even measure it with conventional methods which measure the tough steels.

[Blerv]

M4 is an extremely high carbide steel, even when it is under tempered by almost 10 HRC points it still matches M390 on a CATRA test, which is mainly a test of wear resistance. The biggest difference between the two for a user is one is stainless and one is not. Both of them are extremely brittle steels, with an impact toughness so low you can not even measure it with conventional methods which measure the tough steels.

Interesting Cliff, thanks for that.

I didn't mean to put it in the extreme toughness range of the spectrum. Being far tougher than ZDP-189, CPM-S30v really isn't something to brag about but when edge holding is put into the consideration the picture makes sense. A reason why when ground properly it's a good chopper steel (based on what I hear).

For your use does it make sense over the edge wear-resistant "super" stainless steels?

[Niles]

M4 is an extremely high carbide steel, even when it is under tempered by almost 10 HRC points it still matches M390 on a CATRA test, which is mainly a test of wear resistance. The biggest difference between the two for a user is one is stainless and one is not. Both of them are extremely brittle steels, with an impact toughness so low you can not even measure it with conventional methods which measure the tough steels.

How is impact toughness measured? Does this reflect chopping in regular use, or something more specific?

[MachSchnell]

I was under the impression that M4 sacrificed some wear resistance for toughness. :confused: That's what my searching produced, but you know everything you read on the net is true. :p

[Zenith]

^

That's what I also read. The reason it is used in blade sports by so many makers it can handle thin grind while still being able to take those short spans of shock to the blade while chopping.

[MIL-DOT]

........I recall Sal saying once (don't quote me) something like, "toughness, edge holding, corrosion resistance, price...pick three."

LOL, talk about a blast from the past ! This reminds me of something I read a while ago from a major bicycle designer/builder ( Kieth Bontrager,maybe) who said in reference to bike frames, "Light,strong,cheap.....pick two".
I've since read it in other contexts,some pre-dating this one, so who knows where it originally came from.

[Cliff Stamp]

How is impact toughness measured? Does this reflect chopping in regular use, or something more specific?

Impact toughness is measured by hitting a block of steel with a hammer and seeing how much the hammer slowed down after the block broke. The slower the hammer the higher the impact toughness of the steel. It is a direct measure of the resistance of the steel to sudden gross fracture, i.e., a very heavy load comes on the steel so fast that it can not bend to absorb it.

For knives the impact toughness has a directly significant connection to what happens if you chop into something very hard as you need enough toughness to prevent fracture. It also has a secondary benefit for all chopping because if the toughness is very low then the shock of even wood chopping can cause blade blowouts.

I was under the impression that M4 sacrificed some wear resistance for toughness.

That is how it is hardened for the cutting competitions, it is under soaked to reduce the alloy that goes into solution, hence you see hardness levels which are significantly below how this steel is hardened in industry.

This maybe why people are finding that M390 has greater wear resistance in use as they are comparing it to undersoaked M4 and thus if you look at the composition sheet it is a bit deceptive.

It would be like for example comparing ATS-34 at 54 HRC to 440 C at 60 HRC and then noting that the wear resistance was higher for 440C and thus it had more carbides, etc.. The main influence there would be the large hardness change.

For your use does it make sense over the edge wear-resistant "super" stainless steels?

If you don't want stainless as a property it is always better not to have it simply because it costs to get. If I was getting M4 in a blade I would not want it undersoaked I would run it as it was designed for a cutting tool at 66+ HRC. But unfortunately I can not convince Sal to just make knives for me, though that would be nice.

The way they are currently ran is to provide a mix of toughness and wear resistance and prevent the kind of dramatic failures you can see on blades which are that hard as they are not overly forgiving if you are a bit ham fisted with them. No manufacturer want to see pictures/video's of knives which big pieces missing out of them.

Now interestingly enough, the main reason it is promoted in the cutting competitions is the claim that M4 allows thinner edges than steels like say 52100. This is a rather interesting claim and for a while I just called shenanigans on that because there is no materials data to support it and what data is available would argue the opposite.

For example comparing M4 (vs 52100) with both at 60 HRC :

-impact toughness is lower
-edge stability is lower (deformation on the micron level)
-compressive strength is the same

Thus how can the resistance to deformation laterally be higher?

But recently a few makers who I know don't hype have said their experience seems to be the same, though I wonder again if it is not just retained austenite which they are seeing as this is very prone to be a problem with low tempers vs high tempers and people also do all kinds of crazy things to 52100 to harden it.

Torsional strength curves would measure it directly, however few manufacturers actually do that.