440V [was Is CPM-440V the holy grail?]

Outlaw_Dogboy, hardness measures compressability, very soft blades will deform easily as you noted. It makes no difference how high the wear resistance is because that materials aspect is not being stressed anyway. Note as well that hardness is loosely correlated to strength (resistace to edge rolling), so soft blades tend to suffer from edge rolling as well.

In regards to 420V, I have been discussing this with Phil Wilson, and I will be getting a blade from him at 60 RC in a few weeks. He notes some very strong performance from it, close to CPM-10V in terms of rope cutting and will bend before break in terms of flex. He also notes no durability problems. He does however make very specific use knives. It should be interesting to look at in any case.

-Cliff


[This message has been edited by Cliff Stamp (edited 06 October 1999).]
 
Cliff,

I agree with what you say, entirely. And I guess my disappointment lies in the apparent fact that the way I dull blades is different from the way everyone else dulls blades. For me, it seems a 440V, 420V, or whatever CPM-xxxV blade in a folder would work best if its hardness was bumped up nearer 60. If it isn't, then no matter what kind of wonder steel it is, it doesn't work as well for me as the steel in the cheap Bucks. Yet I have never had a problem with the steel in the cheap Bucks not performing very well in whittling, skinning small game, cutting rope, etc, and maintaining a good edge while doing it. And I can't imagine that a CPM blade in the mid-fifties would handle very well nicking a bone during skinning.

So, why am I paying the extra money for CPM-4x0V blades? (Rhetorical question; no need to answer or shoot flames at me...
redface.gif
, 'cause actually I'm not paying the money for CPM blades anymore. Unless someone makes them harder, which I doubt will happen.)

Anyway, I continue to rant, when there really is no purpose in it. Sorry.

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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
Outlaw, there are people who make them harder. Tom Mayo, Phil Wilson and Ed Schott come to mind and there are others. You might want to discuss the matter with them.

-Cliff

[This message has been edited by Cliff Stamp (edited 06 October 1999).]
 
I also wonder where's the payback in the wondersteels. Knife steels, like jet aircraft, are sometimes evaluated with specialized roles (attack, fighter, interceptor and air superiority), but for the plain Joe on the street, maybe the benefits of one wunder-steel over another gets lost in the multi-role knife we're apt to expect (ie, a knife that can take a staple or two).

Maybe when a steel gets evaluated, it shouldn't just get a grade for wear resistance and toughness, but some kind or figure that averages those two factors together for the folks that use their knives for the whole spectrum of cutting possibilities (ie vs skinning, chopping, or tactical).

Steel comparisons sometimes harken to the days when aircraft manufacturers were on a mission to prove to everyone how fast they can make their bird fly. But a fast plane doesn't make a good dogfighter (nor can a fast plane outrun a Sidewinder).

I mean, what good is a knife blade that can do 1000 cuts thru 1" manila rope and still be shaving sharp, if it chips/rolls on the first staple? Good only to a rope-cutter.
 
Longden said:
I mean, what good is a knife blade that can do 1000 cuts thru 1" manila rope and still be shaving sharp, if it chips/rolls on the first staple? Good only to a rope-cutter.
Click to expand...

Thank you! Why couldn't I put it so succintly, when that is exactly what I meant to say?!

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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
If you want to cut metal with a knife then you should probably use a material that is tough at the high hardness levels that will be required, such as the tool steels and the CPM steels that we've discussed. The 10V is suggested by Crucible as a replacement for carbide tools when chipping is a problem. The ordinary stainless steels especially seem to get pretty brittle when they're pretty hard, and is why they chip and break tips so readily.
 
Johno, that is what I've been saying. The wonder metals (CPM) won't even cut a staple, or bounce off it without severely rolling and damagine the edge, hardened to the levels that I have experience with (the BF Native). That is my whole point of being in this thread... that the CPM wonder steels need to be much harder than they appear to be from production companies - just to get performance in a pocket knife equivalent to that of Buck's 420HC, or 425Mod, or whatever they're using. I can only imagine that the CPM steels used to cut metal must be at much higher hardness levels.

I don't want to cut staples anyway, though; I just don't want to destroy the edge on my premium ($$) knife with wonder steel because I accidentally nicked a staple that is only 0.015 inch, or whatever the office staple is.

Sorry, I just can't stop ranting....
frown.gif


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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy




[This message has been edited by Outlaw_Dogboy (edited 06 October 1999).]
 
I'm not optimistic enough to think that my daily carry could and should cut metal.

As Outlaw pointed out, the run-in with the occasional immovable object is a fact of life for some knives and perhaps mitigates against the use of some specialized steels in a working knife...or at least makes their value and cost questionable to some users.
 
You seem to be confusing how one maker chooses to use a steel in a specific knife with what the properties are for different steels, as I don't think that you're suggesting that there is no benefit in anyone using any steel other than 'Buck steel', as if 425 or whatever it is is plenty tough with good wear resistance at high hardness levels. Since hardness is essentially resistance to deformation it doesn't matter what the steel is, but something like CPM-3V at Rc60 will wear better, hold an edge better, and be much tougher than 425 at Rc60, given the same shapes.
 
but something like CPM-3V at Rc60 will wear better, hold an edge better, and be much tougher than 425 at Rc60, given the same shapes
Click to expand...
johno, I agree with you whole-heartedly and completely, and, from what I can ascertain, CPM-440V, -420V, and/or -10V could be described the same. But, I maintain that 56-58 Rc, a la the BF Native that I have, is too soft, and is certainly not as well at holding an edge as the 425 at Rc60. At least that seems to be the case for me. Fortunately, it's easy to re-sharpen.

Don't get me wrong, though. I like the BF Native. One of the best knives I have. But, I have to think that based on my experience with it, it would be just as good a knife if the steel were ATS-34, ATS-55, or even 425, bumped up to a higher hardness.

I'll shut up now, since after reading this, it appears that I don't have anything else to add to the discussion, and haven't in a while...
smile.gif


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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
I don't think it is a good idea just to up the hardness on the 420/440V steels. I've stated before, 420V has excellent wear resistance as well as toughness, but this all goes out the window as you raise the hardness level. Going from 55HC to 57HC in 420V loses a lot of toughness.

Spyderco heats treats their ATS-34 blades at ~59HC, and their 440V blades at ~56-58HC, and just recently lowered the hardness of their 440V blades to ~55-56HC. Even with the 440V blades having such a low rockewll hardness, Spyderco had to modify their serrations because the 440V blades were more brittle than the ATS-34 blades.
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Johnny
[]xxxxxx[]=============>



[This message has been edited by JoHnYKwSt (edited 06 October 1999).]
 
So now we're back to where we (or I) started: confused as H#&&! Spyderco has lowered the 440V hardness even further?! Good LORD! Why? What does toughness get you? Seriously, I'm not being confrontational; I want to understand. What does toughness in a pocket knife get you?

My understanding is that toughness decreases the likelihood that you'll break or chip the blade during impact. I've never "impacted" anything with any of my pocket knives. (Well, there was that pesky staple; good thing my Native was so soft, or the blade might have broken... OK, sorry, that wasn't necessary.)Or that you can get an edge thinner so you can get better cutting characteristics, without it chipping. But wait, the ATS-34 blades in the Military have more 'acute' (for lack of a better word; can't see what word johnnykwest used) serrations than the 440V version? Doesn't that mean the ATS-34 blade will cut more aggressively? Is the ATS-34 blade harder than the 440V?

Grrr... *mumble, mumble, mumble*... I feel like I'm back in subsonic aero. What do I care about it if I need a Cray to solve the equations?

Sorry, again... I just couldn't stay out of this, because now I'm as confused as ever...

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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
Why quibble over 440v and ats-34 when you can make your knives out of unobtainium?

UNOBTAINIUM:

Rockwell Hardness 97!

Flexible enough to twist into a pretzel and come back true every time!

Wear resistance unmeasurable!

So tough it can pry open a tank turret and stay hair popping sharp!

Even has a self-healing micro edge!

Lynn? Are you listening? Can I have a job?


 
The problem with lowering the RC to gain toughness is that you lose strength. While the edge and serrations will not fracture easily at that low RC due to the high toughness, they would probably roll / impact quite easily due to the low strength. A good knife steel should have both high strength and toughness to both resist deformation and fracture. If either of these is lacking you will notice problems quite readily. Of course what is a "good" level of strength/toughness depends on the intended use of the knife.

-Cliff

[This message has been edited by Cliff Stamp (edited 06 October 1999).]
 
Thanks Cliff. That makes a lot of sense, and gives me something hang my hat on.
wink.gif
so to speak....



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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
Outlaw said: Don't get me wrong, though. I like the BF Native. One of the best knives I have. But, I have to think that based on my experience with it, it would be just as good a knife if the steel were ATS-34, ATS-55, or even 425, bumped up to a higher hardness.

And that is important to know, as common steels are usually cheaper than exotic ones. It also suggests that as I mentioned before, most people seem to place a higher demand on edge holding than on toughness, as they frequently test the limits of edge holding and rarely do so with toughness. But, a brother and a friend have both broken or chipped their Benchmade knives, and at one time it didn't seem unusual to see broken knives, like lots of Buck knives with broken tips. I have the impression that at one time some of the larger makers used harder blades, like Buck and Gerber, and that they have made their knives a bit tougher by lowering the hardness levels and/or using different materials. Finding a thin blade knife with an exotic tough steel at Rc 60 or better should offer good cutting, good edge holding, and the best toughness available at that hardness level.




 
One thing to keep in mind is that Rockwell numbers don't map cleanly between different types of steels. 440V at rockwell 56 is not the same as 440A at rockwell 56.
 
Outlaw Dogboy, does that old Buck of yours have the same edge angle and thickness as the Native?

I wonder if we're really comparing apples to apples here. Maybe all you need to do is sharpen the Native to the same edge angle your old Buck has.

I don't suppose you have any precise way to measure the angles, but try eyeballing them -- if the difference in angle is enough to account for the difference in performance it ought to be detectable to the eyeball gauge.

Besides the secondary edge angle, there's the question of how thick it is. A new knife has a primary bevel that almost comes to the edge and very little secondary bevel, but if you've had that old Buck a long time and like most people you've only been sharpening the edge and never thinning the primary grind, it's gotten pretty thick by now. When the edge on the Native rolls on a staple does it roll past the secondary bevel? That should be visible -- with magnification, anyway, especially if you're a bit farsighted as most people get as they mature.... Try a good 10x loupe in a bright light.

-Cougar Allen :{)
 
In terms of RC, different steels at the same RC will indent pretty much the same as that is what RC measures. The strength / toughness may be radically different, but I would bet that at 55 RC, 440V is of lower strength than Bucks which could be quite a bit harder based on Spyderco's steel chart.

One thing that has to be noted with regards to CPM steels, and any steel with very hard carbides (V, W), is that AO stones are too soft to actually cut the carbides and will only effect the steel matrix. You need a hard cutting hone like SiC or ever better diamond.

-Cliff
 
Cougar, to the best of my ability to measure or eye-ball it, it has as thin an edge, very near the thickness, of the BF Native. If it isn't, it is thinner. Maybe a more acute edge angle as well (I tend to thin my edge angles a lot, especially when sharpening on a bench stone, like I have the Buck). Bottom line, best I can tell, the Buck should be at a disadvantage.

As far as the edge rolling on the Native... I am not sure of the terminology. I understand, I think, the primary bevel and the secondary bevel on a flat grind (secondary bevel is the one you sharpen, right? Trying to keep the same angle?). Does the same terminology apply to the hollow grind on the Native? If so, it does not roll past the secondary bevel, but rolls enough that the blade now has a place on it where you can still see where it rolled. This after sharpening it about 3 or 4 times since. Yeah, I sharpen the Native a lot. It loses it's edge pretty regularly, just cutting up boxes, and opening mail and packages. Occasionally whittling a stick, or trimming a branch off a shrub.

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Sometimes you're the windshield; sometimes you're the bug.
Outlaw_Dogboy


 
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