School me in cpm m4

if m4 can achieve high toughness and hardness better than a lot of steels at very thin profiles, why is it not offered for thickly profiled 1/4 inch chopping knife with a slightly lower hc? Difficulty in HT, price?
 
masa said:
if m4 can achieve high toughness and hardness better than a lot of steels at very thin profiles, why is it not offered for thickly profiled 1/4 inch chopping knife with a slightly lower hc? Difficulty in HT, price?
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probably because choppers themselves are such a small niche, then add in a new premium steel, and it might take awhile to hit the market.

I've seen some cool custom choppers out of it.
http://www.bladeforums.com/forums/s...M4-15-quot-Survival-Chopper-with-Carbon-Fiber

Not to mention all the custom knives in m4 that were used in cutting competitions are refined choppers. Cutting competitions are why the steel became popular in the first place.
 
masa said:
if m4 can achieve high toughness and hardness better than a lot of steels at very thin profiles, why is it not offered for thickly profiled 1/4 inch chopping knife with a slightly lower hc? Difficulty in HT, price?
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Because that would kind of defeat the purpose of having CPM M4 to begin with--its relative toughness at high hardness compared to other steels. If you were going to lower the HRC because you were worried about toughness, then why wouldn't you just choose a tough steel like S7 to begin with?
 
Cynic2701 said:
Because that would kind of defeat the purpose of having CPM M4 to begin with--its relative toughness at high hardness compared to other steels. If you were going to lower the HRC because you were worried about toughness, then why wouldn't you just choose a tough steel like S7 to begin with?
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Isn't it that M4 has better edge retention and toughness at a lowered hardness of say 60hrc than S7 at 60hrc?
If it beats most carbon/ tool steel at 59 60 61 62 hrc in terms of edge retention and toughness, why isn't it be used more? Certainly it cannot be because a not so fine steel is used just because it is all that is needed?
 
of all the "premium" steels that are out there, this is one of my favorites b/c of how finely grained it is
 
masa said:
Isn't it that M4 has better edge retention and toughness at a lowered hardness of say 60hrc than S7 at 60hrc?
If it beats most carbon/ tool steel at 59 60 61 62 hrc in terms of edge retention and toughness, why isn't it be used more? Certainly it cannot be because a not so fine steel is used just because it is all that is needed?
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All things being equal, CPM-M4 seems to be best in the mid to lower 60 HRC. Testing would have to be done to see if S7 and CPM-M4 at the same hardness (60 HRC) are even comparable in toughness. The improvements in edge retention for CPM-M4 seem to be a product of its higher HRC value (given anecdotes from BM's recent increases in hardnesses) which would be negated if one were to keep it at 60 HRC. If edge holding is being passed up in favor of toughness, I question the value of using CPM-M4 at relatively lower HRC values over other, tougher, steels at the same hardness.
 
Skimo said:
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.
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Sorry, I meant average as substrate that knife nuts consider average without too much abuse potential, meaning I'd cut a little cardboard, clamshells, paracord, paper, fingers etc... no zip ties, carpet, heavy cardboard, sandpaper etc... just showing a modicum of care.

Sounds like I should get to re-profiling. I'm not huge on microbevels so I'll probably set it at around 25° inclusive.

Goodeye- yes, I have wanted that chopper for a while now. Just having it would encourage me to spend more time working out my arms. In fact if I had one I could totally see getting involved in the comp!
 
I've never attempted a reprofile on my m4 Millie. it still has basically the factory edge, I have only ever hit it with the brown sharp maker stones, nothing more aggressive. it's somewhere around 30 inclusive, but it gets closer to 40 at the tip because it wasn't ground perfectly from the factory, but it has performed terrifically. The edge is so stable, appearing pristine after coming into contact with things that would noticeably damage a lesser steel.

I would feel comfortable around twenty degrees for light to medium work, but I've never had a reason to change what it's at.I'm not a sharpening elitist, I usually stop when it will barely shave arm hair. But it keeps that working edge for a long time.
 
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my gayle bradley is at 30 degrees inclusive mirror polished up 2 3,000 grits , and all I do is hit it on the strop every few weeks and it's back to hair pooping sharp, I really wanna take it down to 20 degrees inclusive just to see what the steel is capable of, I'm sure it would still handle that much of an acute angle just fine, On another note I live in a very humid area and with minimal care my gayle bradley hasn't even started to patina yet. Still factory fresh.
 
it should also be kept in mind that the toughness of 3V falls off a cliff above 61, above which M4 has comparable toughness, much higher wear resistance, and can be taken up to 64 or 65 and still be a useful blade material. M4 is a high speed steel, it is meant to be run at the higher hardness, you can underharden in the 61/62 range, as competition cutters do to increase toughness while still maintaining the wear resistance advantage, but it just won't peak the way 3V does at 58. Of course, 4V/Vanadis 4E is around and something that fits in that area, as well as something like PD#1. Your desired working hardness is key.
 
hardheart said:
Your desired working hardness is key.
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Well-said. Comparing any given alloy at 58Rc to itself or any other at 62Rc or greater, will reveal huge differences in performance for various tasks.

hardheart said:
it should also be kept in mind that the toughness of 3V falls off a cliff above 61, above which M4 has comparable toughness, much higher wear resistance, and can be taken up to 64 or 65 and still be a useful blade material. M4 is a high speed steel, it is meant to be run at the higher hardness, you can underharden in the 61/62 range, as competition cutters do to increase toughness while still maintaining the wear resistance advantage, but it just won't peak the way 3V does at 58. Of course, 4V/Vanadis 4E is around and something that fits in that area, as well as something like PD#1. Your desired working hardness is key.
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Based on my research into, and conversations with a couple qualified BladeSports competitors, I agree. Those folks are using CPM-M4 because it simply out-performs CPM-3V in pure edge retention at very high hardness levels. (CPM-3V at 58Rc is my personal favorite all-around blade steel... but it's clearly not the best choice for that very specific set of parameters)

Remember, comp-cutters need to accomplish extremely fine cuts like splitting drinking straws, slicing free-hanging cigarette papers and other delicate, highly-specialized manuevers after rough work like chopping through a 2x4... but they do it under controlled conditions and only have to work for a couple minutes at a time. Massive toughness is really not a big deal to those folks.
 
Strigamort said:
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:
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What is this customized Contego you speak of?
 
I know the companies CATRA PDF has M390 with greater wear than Powder M4 ( at rc 61) but I have trouble accepting it when it's running where it really likes at rc 64-65. At that hardness the wear of CPM M4 is closing in on S90V. It's corrosion resistance goes down a bit, the steel isn't quite as tough, but is what I consider very tough for rc 64-65. Tougher than M390 which can only go rc 61 when everything goes just right?

Mostly I like the edges and bite the Vanadium and Tungsten, moly carbides give. The edges can get a pretty savage feel to them. It's certainly in my top 5 or so steels could easily take the "one knife for the rest of your life" answer to the thread that keeps reoccurring every few months or so.

I do just like the way it cuts. In fact I like the high speed class of steels beginning with M2. Also a nice steel when pushed hard. I first ran across high speed steels in a home made garage built knife I bought from an estate sale and it was there I first found the "paper cut" feel edge I found so common on HSS's. Especially the M series ones. I was more used to the W2/O1/1095 type steels with low to moderate carbides and the high percentages of Tungsten, and moly as well as vanadium really caught my attention.

I've been fond of them since. IMO CPM M4 is one of the best of the class for cutlery EDC use.

Joe
 
james terrio said:
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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True, but we FREQUENTLY draw a board that has knots or see one in practice. Generally you try to avoid them in comp, but it happens.

M4 is tough enough for anything I do, but as you say, it holds a fine edge like few other steels I have experienced.

A typical competition includes cutting at least 3 2x4s, a 1 inch, 1.5 inch and a 2 inch hemp rope, two golf balls, some 3/4 inch red oak dowel, half a dozen aluminum cans, and perhaps half a dozen water bottles...and all my m4 knives will still shave arm hair effortlessly after a competition.

For a folder or small fixed blade M4 is a wonderful steel, but there are many others that probably perform as well, but for competition...it shines, and I have not talked to any competitors that have found anything they would rather step up with (and trust me, they are all looking for a competitive edge).

james terrio said:
... but they do it under controlled conditions and only have to work for a couple minutes at a time. Massive toughness is really not a big deal to those folks.
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True, but I will add that competition is game day, and the good guys will often use the blade less than one minute!

However for every minute of competition, I log perhaps 50-100 hours of continuous practice (I don't compete very often). My point is, some make the mistake of thinking our edges only need to (and therefore only do) last a minute or two. I generally strop my blades for a minute or two after each practice session (generally lasting a couple hours) and only need to (truly) sharpen it once ever 4-8 sessions. At that point it will still rough shave arm or leg hair, but there will be small nicks in the blade that impact slicing performance.
 
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So I got to looking at the edge on my Contego just now. There's a small roll and I can't imagine what it could be from. I've only cut cardstock, clamshells and other light duty stuff. Like I said, it's small, but it'll pull on my fingernail pretty hard. Also this is a pretty obtuse edge, factory bevel honed on a wicked edge.

Here's a couple of pics through my loupe.

IMAG0754_zpsc4685745.jpg


IMAG0755_zps2bafa151.jpg


Am I expecting too much?
 
yes, it's a knife edge, sometimes they take damage. maybe you hit a small piece of staple you didn't see. maybe the factory edge had a wire edge, who knows. If it's not in a 100% controlled environment, and it's a one time thing I wouldn't worry about it.
 
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