AUS-8, 420HC, 440A or 440C?

[WYK]

One has to explain why I should use a steel like D2 if it is neither fully corrosion resistant, nor it gets really sharp, it isn’t easy to heat treat or sharpen by easy means you cant make thin and blades and after a polish you see the ugly monster carbide structure with bare eyes.

I sort of agree. All except the 'fully corrosion' resistant part. No stainless steels that have mainly Iron in them are fully corrosion resistant without some sort of coating like Tennifer(tm). I consider D2 more of a stainless, though, than a Carbon. I have had all manner of stainless EDC's rust on me - including 440C. In a dry, cool environment, stainless is generally stainless. In 85 degree and 80% environment, with an EDC carried in the pocket for 8-12 hours a day - it will rust readily. You must keep a thin coating of oil or some such on the blade. So, what's the advantage? There is none. You may as well go with M2 and keep a thin coat on it, too.

WYK

 

[Tzvi]

Roman and Cliff, good informative posts.

I especialy liked the magnified pics roman, thanks.

Both of you doubt s30v was made especialy for knives, and I just did a simple search...and:


2001 - Developed stainless tool steel CPM® S30V® for applications requiring improved corrosion and wear resistance.

http://etoolsteel.com/literature/keyDevelopments.cfm

und

"Our work paved the way for superalloys to be accepted in the aerospace industry and involved baseline work on the processing, alloy modification and the understanding of the physical metallurgy of P/M alloys."

No where in this piece of company lititurature does it even mention knives.

Here is a brochure from CPM in the Plastics Molding industry (dies/tools/molds) and the use of S90V and S30V steels (as well as 440c etc.):

http://www.crucibleservice.com/datash/PlasticsBrochure.pdf#search='s30v%20%20applications%20development'


( ED. look up "crucible mold and tool steels for plastics" as the link does not "come out" as a link here.)
It does mention AMOUNGST MANY the uses of S90V for knives, but not S30V, for whatever oddball reason.

It is most logical to conclude that S30V was not made EXPRESSLY/Exclusively for knives, and it is just good niche marketing on the part of some to state that "this steel was designed for you" buddy.

 

[Sword and Shield]

I sort of agree. All except the 'fully corrosion' resistant part. No stainless steels that have mainly Iron in them are fully corrosion resistant without some sort of coating like Tennifer(tm). I consider D2 more of a stainless, though, than a Carbon. I have had all manner of stainless EDC's rust on me - including 440C. In a dry, cool environment, stainless is generally stainless. In 85 degree and 80% environment, with an EDC carried in the pocket for 8-12 hours a day - it will rust readily. You must keep a thin coating of oil or some such on the blade. So, what's the advantage? There is none. You may as well go with M2 and keep a thin coat on it, too.

WYK

I've never had D2 rust in any way, and I work outside in high temp and humidity every day. I have had 420HC rust in that, but never D2. No special care, just wiping the blade on my pants when I'm done.

 

[Roman Landes]

http://www.messerforum.net/attachment.php?attachmentid=12438

I have had ATS 34 to rust.... mom used it the the way she does to all knives

Her the reason beside the sloppy care, the heattreatment is the cause.

Never make tempering around 550°C where the secondary hardening maimum is, when you want to have corrosion resistance...


D2 at the same place would have looked even worse, because most of the chromium is stuck in the carbides.

 

[yobbos1]

Pick yourself a medium/average grade steel(by todays standards mind you)440c or AUS 8a and get into the Zen of freehand sharpening. Works for me.

 

[Ebbtide]

Curious as to which steel most of you feel is the best of these three and the strengths and weaknesses of each. Just trying to get an idea of which one's are exceptable when I'm out knife browsing, and all of these seem to be pretty popular from what I've seen. Thanks for the info.

I would except the 440A and be fine with the rest.

 

[Cliff Stamp]

...drawing

In paint, so its crappy :

http://i7.photobucket.com/albums/y269/CliffStamp/misc/secondary_edge.gif

The one on the left is most edges from the factory, the one on the right is what they look like after I sharpen them. The one in the middle is a blowup of the very edge which shows a really tiny secondary micro-bevel.

One has to explain why I should use a steel like D2 ...

Try a knife from Dozier. I would not argue that M2 would not be a better choice, but he does make some really nice knives out of it. High initial sharpness, solid edge retention. Forget the tactical models, get one of the utility cutting ones. Lots of great choices, I would go with :

http://www.agrussell.com/knives/handmade/dozier_knives/dozier_whittler.html

Krein also would be worth looking at.



-Cliff

 

[Roman Landes]

Thanks for the drawing Cliff, it is what I thought.

The only change you make is you thin out the crossection so the wedge effect gets reduced.
Than you employ the "Dull edge again"
Basically wise, because to manny thik blades around, but it doesnt do much to the actual edge angle

So the result is a reduced crossection and a "dull" angle on the edge.
Of course you need it, because something like S30/60/90V, D2 has a low stability of the cuttingedge and would chip even while sharpening the thing to a fine angle.

Regarding D2, I made several knives out of it, some 12-15years ago but i never got convinced, except from the point that you get it almost everywhere.
And no matter who works it or heattreats it, the physics are the same to all of us.

 

[Cliff Stamp]

Of course you need it, because something like S30/60/90V, D2 has a low stability of the cuttingedge and would chip even while sharpening the thing to a fine angle.

I have lots of those steels at low angles, 5-10 degrees, they won't chip on soft media, woods, cardboard, ropes, etc. . I just use 20 most often because it was where I run most cutting comparisons as it is a standard edge angle. The only real need is to set it higher than the primary edge grind.

And no matter who works it or heattreats it, the physics are the same to all of us.

Lots of people use D2 and get excellent edge retention, some have in fact made their name based on exactly that. So it would be informative for comparison purposes when you say something like D2 can't take or hold a fine edge if you have used knives from makers who say the exact opposite. It may just be that your standards for a fine edge and edge holding are a lot higher than most.

-Cliff

 

[Roman Landes]

How did you make the comparisons? Freehand or fixture?

of course there are differences in defining what is sharp.

To me the test of sharpness is
hold a hair between your thumb and a finger free standing then cut the hair only by using the counterforce produced by the flexibility of the hair itself.

This indicates that sharpness is definately lower than 1µm on the edge.
This you can do easily with carbon steels, the coarser the grainsizer (carbides) the more difficult it is.

But this only indicates that you did a good job in sharpening it and using the right methode you can do it with alost anny kind of material if you know how.

More important is the stability of the fine edge od lets say "edge retension", means for how long can you do this.
That is definately differnet wether you use D2 or O1 simply because the monster carbides in D2 chip.

And you are right, most users are satisfyed with this kind of sharpness and edge retension that is fair business

But for those who want more (e.g. original japanese sushi knives) there is more and you discribed one of the most important factors yourself: geometry.

For the "more" these steels dont perform well enough

 

[Cliff Stamp]

How did you make the comparisons? Freehand or fixture?

Most cutting I do freehand, some is partially jigged like rope cutting which is done in a track in a piece of wood to keep the rope stable and suspended slightly over a cut out so the knife just hits rope itself.

I generally do most cutting freehand because I want to keep the random lateral stresses that a knife will see if used by a person. If I jigged it so the forces would be all vertical load the results would stop reflecting actual usage blunting.

To test sharpness I use a bunch of different methods, I cut light thread and measure the tension, or light cotton on a draw and measure the length of edge under a specific tension in the cotton, plus other usual more subjective benchmarks like shaving, newsprint etc. .

To me the test of sharpness is
hold a hair between your thumb and a finger free standing then cut the hair only by using the counterforce produced by the flexibility of the hair itself.

That is decently sharp, most knives don't come like that. That is the ability to shave above the skin, Spyderco does it decently often, but not all the time. Dozier can do it with D2. Of course it depends on the coarseness of your hair and the distance between the fingers.

Here is shot of a few strands of hair whittled with a S30V blade :

http://i7.photobucket.com/albums/y269/CliffStamp/misc/hair_whittling.jpg

-Cliff

 

[Habeas Corpus]

That is the ability to shave above the skin, Spyderco does it decently often, but not all the time. <snip> Of course it depends on the coarseness of your hair and the distance between the fingers.

You can say *that* again. I always wondered why I didn't get my knives sharp enough to shave above the skin. Then one of my friends tried my knives, and they did in fact shave above the skin with no problem at all. Looks like my fair is just too soft and flexible.

Maybe we need some sort of standardized hair for that kind of test ...)

Hans