Which tool steel do you prefer in a folder and why?

I am going to have to go with 440V for edge retention and corrosion resistance.
Second choice would be BG42 (Sebenza baby) for the same reason.
Hard to compete with or beat the above choices.

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*Norse Knife Nut*

"Military" Fans Unite!!

"The only limitation is lack of imagination."

 
CPM rates 3V as the same as 420V in terms of abrasion resistance and 3V as being 8 times as durable in terms of edge impacts. It would actually hold an edge much better than 420V and of course be much more durable.

Anyway even though a folder in say 3V as compared to 15V would have lower abrasion resistance abrasion resistance (25%) the toughness jumps by 400%. This means the edge will be much more durable. With any decent steel I have found that the edge always wears out by deforming rather than actual having metal scraped away so I need a very durable (high impact toughness) edge.

I also like high toughness steels as I can then get the knife made proportionally thinner and still have the same strength. This means of course that they cut that much better. A 3V bladed folder could be made much thinner than a 420V one (its 8 times as tough) and would easily out cut it and still be much tougher.

(all these numbers are off of CPM site, if I am reading them incorrectly let me know)

Yeah I have cut PVC pipe. I worked in construction for 3 years.

-Cliff
 
If CPM3V has the same wear resistance as 420V and is tougher, I have a new favorite folder steel, but that was not the impression I got from reading Phil Wilson's article on 3V. Nor can I find any info on 420V or 440V on the only Crucible web site I know about (www.crucibleservice.com). If there is another one, please let me know.

Harv
 
Harv; the reason you cannot find CPM440V on the Crucible site is that it is discontinued.

Cliff: I believe that you are basing your comparison on a chart in the Plastics Tooling section of the CPM site. If this is the case, then you are extrapolating perhaps too much from a simplified chart, designed to give you an overview.

I shall e-mail you each the data sheets for CPM-440V, CPM-420V, and CPM-3V, courtesy of Ed Schott. With this much more detailed and comprehensive information, you should be able to refine your hypothesis. I anxiously await your results. You are both on the right track. Walt
 
I picked D2 personally because the topic was about tool steel's not stainless steel's. Since that seems to have changed my personal pic would be Talonite! Now that is really changing the thread eh?
biggrin.gif
Actually it is a toss up. I am not so sure 420V would not be better. I would like to test to identical folders. One in Talonite and one in 420V. Does anyone know if Kit has completed his comparison of Talonite and Stellite.

Regards,

Tom Carey
 
Kit is making me two Talonite folders, his large one, #18. I have one of his folders in 420V. Will be able to test the two directly, side by side. Walt

PS: Harv and Cliff; don't forget to look at the extreme change in the Charpy tests with CPM alloys as the Rc changes. When it gets harder, the toughness goes down dramatically. Just as you may have already surmised. I anxiously await your report. WW
 
Well, then we have our solution, San-Mai steel with a 3V outer and one of the really hard CPM's for the middle.
Aaron

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Why did you stab that girl?
You won't believe this, but I had too much coffee!
-Edmond by David Mamet
aaronm@cs.brandeis.edu
 
Dr. Walt,

Thanks for the spec sheets!

From the spec sheets I have gathered the following information:

CPM420V at 55/56 RcH has a Charpy toughness rating of 22 and an adhesive wear resistance rating of 35. At 57 RcH, toughness is 12 and wear resistance is 35/40.

CPM3V at 58 RcH has a C. toughness rating of 85, and adhesive wear resistance rating of 8. At 60 RcH, Charpy is 50, and wear is 7.

For comparison, D2 at 58 RcH, has a Charpy rating of 22, and a wear rating of 3/4.

As Dr. Walt points out, as 420V gets harder, its toughness goes to heck, and at best seems to only be about as tough as D-2, which is not well known as a tough steel but performs extremely well if properly tempered.

On the other hand, 3V appears to be extremely tough while wearing even better than D-2 which is known for holding an edge extremely well.

My conclusion is that 420V is plenty tough if not tempered too hard, and presumably, based only on abrasion resistance specs, would hold an edge better than 3V. On the other hand, a 3V blade should hold an edge plenty well enough while offering huge toughness (hmmmmm, makes one want to speculate about the origins of INFI).

Given the ease of sharpening implications, I think I would definately prefer 3V for a large field knife over about 4", but I will stick to my choice for the best folder steel. I think 420V is tough enough for folder blades, and should hold an edge better. If you think the handle and pivot of your custom folder will stand stresses that would break or chip a 420V blade, CPM3V might be the steel for you.

Harv

[This message has been edited by Steve Harvey (edited 11 March 1999).]
 
The info I was basing my comments on came from the various charts on the CPM site. They list all their products and rate them in terms of toughness and abrasion resistance. This is what I collected:

grade RC range abrasion resistance : toughness

420-V 56-58 7:1


10-V 58/60, 60/62 9:3


15-V 58/60, 59/61 11:2


3-V 58/60 7:8

As you can see from this 3V is clearly superior to 420V. This however made little sense to me so I emailed CPM asking them if their charts were all inline referencing the same baseline, but all my emails just bounced.

Anyway based on the info Walt sent me the above is not even close to being correct. 3V and 420V are basically seesawed in terms of toughness and abrasion resistance. 3V is like 4 times as tough and 420V is 4 times as abrasion resistant. However as Steve pointed out even though a fair bit lower than 420V, it looks like 3V has the abrasion resistance of D2 at about 62 RC while being much tougher. This is extreemly impressive.

Anyway, the reason toughness is important is that you obviously don't make the knives with the same geometry. Since 3V is so much tougher than 420V you can make the point and blade that much thinner and of course grind the secondary bevel that much thinner. This means the knife will outcut the 420V blade by a wide margin and still have the same gross blade strength and impact toughness.

For example along the same lines of reasoning, the tougher tool steels are prefered over the low strength stainess ones (like 440A) because you can make the knife that much thinner. A well made knife out of 440A at say 3/4" thick would be extreemly sturdy and well suited to pry with. However it would be good for little else as it would cut like a pig. If you take a really tough steel like L6 you can reach that level of toughness with a much slimmer blade thus retaining the strength and still being able to cut well because of the much slimmer profile.

Anyway, if the knife was just going to be used for light use like on rope, cardboard etc. then neither aspect of toughess comes into play and you might as well just get the better abrasion resistance of 420V.

-Cliff
 
definition of tool steel...more than one percent carbon...end of story...for those who want to exclude a lot of "stainless" steels they need to take it up with the AISI, and steve...sorry but 440v is not nearly as tough as ats34.....although it sure takes a better edge.....all this sounds great...but are any of you guys using theses steels??? how do they hold up....i know phil wilson is field testing all this stuff...by the way....i tried to get paul bos to step back the rockwell on some 440v so it wouldnt be so brittle and he told me the corrosion resistance goes out the window when he tempers them back below 56....something to think about...especially when you live in hawaii......

[This message has been edited by tom mayo (edited 14 March 1999).]
 
It seems that this thread has exceeded its' original parameters, yet still has excellent potential. To help realize this potential, I have posted a new thread on this forum, New Alloys, Hot or Hype. Feel free to contribute there or here, however keeping it in one place will be much more easy to follow.

Harv,Cliff; since you guys already have the CPM data sheets, feel free to post away; however, since, at least for now, virtually no one else has them, you should, IMHO, refer to them very thoroughly, citing numbers if possible. Thanks, and see you there. Walt
 
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