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

C

Cliff Stamp

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In the following thread on the old general forum :

http://www.bladeforums.com/ubb/Forum1/HTML/005052.html

JoHnYKwSt :

when I said that 420V advertises excellent toughness as well as edge holding, this is compared to other stainless steels.
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What are you basing this on? Crucibles own spec sheets places CPM-420V as being slightly better tham CPM-440C but significantly worse than 440C (the charpy value is almost 50%).

Ken Onion :

I doubt that you will need great impact resistance on your pen knife as you won't be choping with it in this case you would opt for a steel with great edge retention .
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As Joe pointed out, you can't have great edge retention without the necessary toughness to keep the edge from fracturing. This is the case for example with ceramic as pointed out in the current thread in the reviews forum :

http://www.bladeforums.com/ubb/Forum3/HTML/000890.html

While ceramics and ceramic composites have great wear resistance, I would not say they (in general) have high edge holding as related to regular utility knife usuage. They simply don't have the necessary toughness and chip out easily.

-Cliff
 
Cliff,

I'm sorry, but I don't understand what you are saying. Are you saying that 420V is not a good material for blades? How does does it compare to 440V?


Don
 
Don according to CPM, 420V is directly superior to 440V. It has better wear resistance (twice), better toughness (a little like 25%) and better corrosion resistance (twice). The central point is the toughness. To be specific, to get the toughness of CPM-10V at 63 RC, CPM-420V needs to be left lower than 57 RC and 440V even more so. There is a huge difference in how a 63 RC steel blade will behave and a <57 RC one. As another example, at 59 RC D2 has a decent level of toughness. To reach that in CPM-420 you need to drop down to 55 RC. And again there will be a huge difference in performance between the two.

However I will state again that my opinion is just based on what I have read from CPM and some reports from members on their CPM 440V blades. You cannot simply ignore the fact that there are many people working with the CPM 440V/420V steels that do regard them highly. Ed Schott has stated CPM-420V outperforms any other stainless he has used, Tom Mayo has praised 440V a number of times, Darrel Ralph uses 420V, and there are others. It would be interesting to know if these people are heat treating the steels as CPM suggests or are they using different methods.

-Cliff

 
I'm so f*****g confused I can't stand it. I keep hearing that CPM-4?0V is as good as it gets, if you're staying with steel. To get any better, it has to be Talonite, Stellite, or some other exotic, cobalt {?} based material.

Yet, I then hear that to get the best performance from CPM-440V (that should have been in there when I first put this reply in) (good toughness?), you have to drop the hardness down to the mid-fifties. OK. But, it seems to me that at the point the steel is so soft that it won't maintain an edge. My BladeForums Native certainly supports that hypothesis. It holds an edge about like my GIN-1 Native. And heaven help you if you happen to nick anything harder than the mail, the morning cereal box, or the packing tape. My Buck's in their mystery steel will hold up better to nicking something harder than cardboard. Don't get me wrong, I love this knife, but certainly not because of the edge holding. I'd love to get another one, but I'd come even closer to getting it if it had the GIN-1 blade and the corresponding (hopefully) lower cost.
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Meanwhile, my ATS-34 blades just keep cutting and cutting. Need some heavy work done? I grab something with ATS-34 (and not because I worry about damaging the BFN; I just got tired of working the bent edges out of the 440V when the ATS-34 could take it and keep going).

So why is it that everyone except me swears by CPM-4?0V being the best performing steel?!
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OBTW, sorry for the rant....

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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 04 October 1999).]

[This message has been edited by Outlaw_Dogboy (edited 05 October 1999).]
 
Will there ever be a holy grail of steel? I have my doubts. It's all about trade off's. You have to ask yourself what matters most. I for one would not even consider a stainless steel if toughness and impact resistance was the most important factor. One must look at what they will be using the knife for and then decided which blade material best suits their need. I suspect sometimes the best answer is two knives in different steel's that will be used for different tasks.

Regards,

Tom Carey
 
With the advent of the various internet resources, the knife user has become much more informed about steels,alloys, etc...It wasn't like this even ten years ago, but know, the more educated users are educating themselves in basic metellurgy (and some companies are using this to their advantage with advertising, etc), which isn't a bad idea. But, as happens in most high end hobbies (I can spout-off all sorts of battery lingo from my R/C car racing days) it becomes a race to see what is best, and why and to whom? As the user becomes more educated, the products and materials come under more scrutiny. What's best? Heck, I do not know. I use what I like, and what I feel it's worth. Like most on these forums, I want to know the "whys", and become as educated as possible, as it's part of the mystique, but at the same time, I would say that the highly educated user must not get so involved in minor symmantics, or you all will go loony!

--dan

 
Heh. You know, I've ceased wishing that things would become so simple that there was just one "best steel", and that was that. Where's the fun in that? I'm coming to believe the greatest part of this hobby is hearing about the new ultimate steel, believing the hype, getting all excited, testing it and finding out that it has advantages and disadvantages like any other steel, and then continuing the search
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I keep coming back to the same conclusion: it will never suffice to try to understand steels as a simple ordering of best-to-worst; rather, the only way to do it is to understand each steel's relative advantages and disadvantages versus the others


Joe
jat@cup.hp.com
 
I suspect that for most people edge holding is the more important attribute, maybe more noticed is more accurate, as few will be willing to test the toughness of an expensive knife especially. In another thread I made a comment about banging on the end of a knive like a wood chisel, and I took another look a cheap ($6 ?) Stanley wood chisel that I have. It appears to be carbon steel as there is some rust, it's 1/8in thick and is about 3/4in wide, is pretty hard as it's a pain to sharpen, takes and holds a very good edge, has a plain black plastic handle that seems to bear on a shoulder on the blade, and takes a beating as I usually wail on it with a claw hammer. I haven't tried using it as a pry bar but I have pried with it as I pop wood out. Although there may be problems with some solvents the plastic handle otherwise is very, very tough and might be a good material for knife handles. It seems like a good choice of materials for the design, intended use and cost, which seems to be the key as others have mentioned.

I wish my planes would hold a better edge though, but I guess that's what I get for buying old ones at garage sales and such. I need D2 or CPM-10V blades for my planes :^)
 
Cliff,

According to the spec sheets, 420V is much more wear resistant than 440C; and 440C's toughness is a little better than 420V. Taken as a whole, 420V's wear resistance beats 440C's wear resistance by a wide margin, while only losing a little toughness compared to 440C.



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Johnny
[]xxxxxx[]=============&gt;

 
Johnny -- but of course it's not quite as simple as that. If you're doing a slightly harder job that's tough on an edge (.e.g, chopping, or even cutting cardboard), most of your edge wear may come through chipping, so for these types of jobs 440C's toughness could be more important for "edge holding" than 420Vs wear resistance. Which is what Cliff has been saying for a while.

Another point Cliff makes is that that given a certain level of edge toughness, you can make the 440C edge thinner (and thus have better performance) than the 420V edge. So the 440C blade will take less strokes through the material. For this kind of testing, you want to control for toughness and see if the extra performance of the thinner 440C edge is more important than the absolute wear resistance of 420V. I don't think *any* of us have ever really done this kind of test, taking the tougher blade thinner and doing a re-comparison. We usually control for edge thickness and test toughness and edge holding from there.

Joe
 
Another potential drawback of CPM420V is that it holds an edge too darn good. I don't think I would want a big field knife made out of a material that abrasion resistant. If you severely dulled it, as would be possible to do in a semi-crisis situation, you might have a heck of a time getting it good and sharp again.

Great for small utility blades though, where chopping strength and sharpening are not such a big deal. I believe it is tougher than ATS-34 which is serving pretty well in a lot of field-grade knives presently.

Taking the same notion a little further, Talonite is hard to beat for medium utility folders where again chopping and combat abuse are not expected.

There is no holy grail in my opinion, just a pretty wide variety of steels that perform amazingly well if heat treated correctly, and a few specialty blade materials that do certain things extraordinarily well but are less versatile.

CPM3V seems like a hard to beat steel to me right now for hard-use knives like big hunters and bowies. Way tough, and darn good edge holding too. But I don't care much about stain resistance. I maintain my blades, and don't really care if they turn a little grey. You would want something else to keep racked-up next to the fish cleaning table day in and day out though.

Harv
 
I thought that the conclusion was that differing steels for differing needs.

I prefer a cpm420v steel in a folder, where I'm not doing any chopping, but where I would like a stainless, cause 1) I can't always clean it when I want and 2) I use it on food where I prefer a stainless blade. On a big knife or sword I would want a carbon steel that was set up to take punishment. On a medium size knife I'd want a cartbon steel like D2 or maybe BG42 if I wanted a stainless. Again it depends on it's use. A kitchen knife I'd go with a carbon steel because it's in the kitchen I can clean and dry it right away. On a field kitchen knife I'd want a stainless, cause when I'm out at the field I know I can't always clean up properly so I make allowances.

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~ JerryO ~
 
Outlaw,

The CM440V blade on your Native shouldn't exhibit the problems you're having. I've had CPM440V blades for 5 years now and find their edge retention better than other more common stain resistant steels. Now I don't have CPM420V, 10 or 3V though, but I have found Talonite to easily best my stainless and tool steels in edge retention.

Joe is absolutely correct. Each material may depend on other factors such as heat treating or edge geometry, so it is difficult to say one is better than another without an awful lot of qualifications. There are always trade offs although some materials much less than others. But then again some generalities are acceptable such AUS-6 and 440A are in a much lower class than 440C and BG-42. Here it is implied that with the best of everything (treatment, geometry, etc.) one group simply doesn't match up well compared to the other.

Among stain resistant steels I think the CPM stuff is in a class by itself period, be it 3V, 10V, 420V, or 440V. Tool steels such as A2, 5160, or 51200 offer a great deal of benefits as well. Then there are the exotics like dendretic D2 and Talonite which afford their own set of superb characteristics.

So, for Cliff, is CPM440V the holy grail? No, but nothing is. I laud Talonite because for my use it meets my needs better than anything else overall. Nope it isn't the holy grail either, but the trade offs are minimal in the geometries I have it in. But I still value my other blades of A2, 5160 and CPM440V as they deliver too but with their own set of trade offs.


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-=[Bob Allman]=-

I did NOT escape from the institution! They gave me a day pass!

BFC member since the very beginning
AKTI membership pending
VHA and NRA member

 
Outlaw, that is pretty much exactly what I have been saying. Most people in this forum don't have great things to say about 420-J2 for example, the primary reason is that knives made from it are always soft. It is very easy to roll the edge and even indent it significantly. If you take 440V/420V and make it soft like 420-J2 you will get similar levels of performance when similar stress levels of a specific type (compression / shear in this case) are applied.

High wear resistance is great to have in a steel, there is no question of that as it prevents the loss of excessive amounts of material being ground away from the edge. However it is just as important to have a very rigid material (high RC), and a very tough material. If the steel is very hard it will resist deforming. If this is the case you can grind it very thin and put a very acute bevel on it. However the steel also need to be very tough or this very thin edge will break apart.

Just imagine the edge of a knife blown up and you standing on it. Now imagine ripping this quickly through a piece of cardboard, for example a package you got in the mail. There will be surface dirt present on the box and grit in the cardboard. These little specs will seem like rocks from your point of view and while some are grinding along the edge wearing it away, others are slamming into the edge at high speeds trying to fracture it. As well you don't tend to rip in perfect straight lines perpendicular to the edge (I don't anyway), and if this is the case you will get cross stresses straight across the edge tending to deform it.

However it does need to be considered what kind of use you intend the blade to be used for. For example, if you are just doing light cutting like meat/foods etc., there will never be hard impacts seen by the edge. This means you don't need high toughness so you can take 420V and make it very hard. This way you can grind a nice thin edge on it and it will resist wearing for a long time. Phil Wilson makes knives out of 420V and leaves them at 60 RC and I would bet they are very good at what they are made for.

All I am saying is that in general, high wear resistance does not equal high edge holding. There are other factors that need to be considered and how much of each factor is necessary depends on what you are doing with the blade.

-Cliff

[This message has been edited by Cliff Stamp (edited 05 October 1999).]
 
I don't suppose there's any kind of simple home test for steel RC?

For members like Outlaw who might have a blade with suspect heat treatment, being able to test it without shipping it back to Spyderco, might answer some questions about edge holding (or lack thereof).

Would be nice if there were something like an expensive scratch test kit with tips of varying hardness...start with the softest and work your way up till you get an impression on the blade...and maybe that can be an indicator of the hardness? Maybe even spring loaded to use a consistent pressure.

Anything out there like that? This would be a hit at the BF store, I'd bet.
 
You can get files graded exactly for that, but those that I have talked to don't speak highly of them. What you could do is drop by a local university. As long as you agree not to publish the results, the engn. lab would probably do a quick test for you. Of course a lot of knifemakers have RC testers as well so check with any that live nearby.

-Cliff
 
Thanks Cliff. I live in Ventura, CA but I'm loathe to ask the folks at Cold Steel (they're based here) to test my Spyderco BF Native.. they may skew the results and give me a new blade thumbhole
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I'm taking a night class at the local community college, but I doubt that their engineering gear is up to snuff with a university.

Does anyone ever do RC testing at the knife shows? I'm going to Blade Show West next week.... tho I imagine an RC tester wouldn't be a big draw item and probably more trouble than it's worth to bring along.
 
On hardness vs wear resistance contributing to edge holding.....there is probably more variation in wear resistance of the materials chosen for knives than there is in hardness, as most hardness levels seem to fall in a rather narrow range and have been in that range for quite awhile. The major improvements that we've seen in edge holding seem to largely be the result of improvements in wear resistance.
 
Please note my edited post above, in the second paragraph.

Regarding the hardness of my BF Native... I believe the hardness is very probably where it is supposed to be. I have already asked Sal about what the hardness should be, and he stated that it should be the same as the Military, which comes in at... stby, gotta look
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... 56-58 Rc. I think that is where I'm having all my confusion. It needs to be that soft {?} to get good performance, supposedly. Yet, by the terms of performance that I am looking for (holding an edge cutting cardboard, paper, crusty bread, plastic, grass rope, nylon rope, wood) it doesn't seem to hold any better edge than the GIN-1.

Specific example: I regularly cut articles out of magazines that I want to keep. Before I became enlightened
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, I used a Buck Colt to do everything, including this clipping. I occasionally (OK, regularly) would nick the blade on one of the staples. Well, now, of course it wouldn't shave after that; but, it would keep right on digging through the paper, cutting like a champ, with no problem. The edge didn't chip, and it didn't appear to roll. If I continued to hit the staples, it would eventually start dragging to the point that it would rip the paper instead of cutting. (All this was being done with the tip, using the knife like a scalpel, cutting through the magazine laying on a desk top) But, it was acceptable edge holding. Now, zip forward to my enlightened period, where I am using the BF Native to do the same clipping in the same way. Seeing as how it is a much more expensive knife, I really tried to be careful to miss the staples, but eventually nicked one.
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Severe rolling of the edge, with associated loss of cutting ability. Now, I could cut the knife some slack, since we are talking metal staples, except the Buck had encountered the same problems/staples, and handled them better.

So, how would the 440V in the BF Native have held up if it had been a higher hardness? Anyone know? Because I would hope for at least as good as edge holding from the 440V as the 420HC or 425Mod, or 440A in the Buck (it is an old pocketknife, and I have heard that Buck used to use 440A). That is the source of my frustration with the awesome 440V!
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Am I the only one who occasionally nicks something that he isn't supposed to??
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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 05 October 1999).]
 
Looking at the bar graph on the spec sheets for 420V showed that 420V had a much better wear resistance when compared to 440C, and 440C's toughness was only better than 440V by a small margin. Looking at the spec sheets in more detail however showed that at ~55RC 420V's toughness was about the same as 440C. But when 420V was hardened to ~57RC, it lost about half it's toughness compared to 440C at the same hardness level. Only goes to prove all steels have their trade offs.

Does anyone have spec sheets for BG-42??

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Johnny
[]xxxxxx[]=============&gt;

 
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