Your experience sharpening super steels?

[ejames13]

'Super steels' wouldn't be 'super steels' without the carbides that make them so. The carbides in super steels are WAY, WAY harder than Mohs 7-7.5; more like Mohs 9+, in the case of vanadium-heavy steels (30V, 90V, 110V, etc). Natural stones of any kind won't touch that, as they're nowhere near hard enough to abrade those carbides, and therefore will stop working as the carbides get in the way at finer grit levels. Even at very coarse grit, lesser abrasives won't cut or shape the carbides and will instead just scoop them out of the matrix steel, limiting how refined the edge can be made. At finer grit, the less-hard abrasive is no longer big enough to dig down between the carbides, which means it only 'skates' across the carbides without cutting them, and effectively stops working.

The Mohs reference for hardness is misleading as well. Being a completely unitless scale, instead simply an ordinal one, Mohs doesn't indicate the true degree of hardness difference between materials, instead only indicating that one is ranked harder than another, no matter how much difference there likely is between them. It's the same type of ordinal ranking as might be seen in posted race results, only indicating the finishing place of each contestant (1st, 2nd, 3rd,..., 8th, 9th, 10th, etc), regardless of how fast or slow each was.

On a scale of actual measured differences, when comparing basic steel hardness to the hardness of the carbides, steel itself (w/no hard carbides) is about 600-800 on the Knoop scale, and vanadium carbides are around ~2800 Knoop (at least 300-400% harder). Even 'softer' carbides, like chromium carbides in steels like D2 and ZDP-189, are about 2X as hard as the steel matrix itself (chromium carbides = Knoop ~1300 or so). Natural stones, like Arkansas stones, are no harder than ~ 825 Knoop (the hardness of the novaculite natural abrasive in them).

A more meaningful hardness comparison, for reference:

Basic, hardened cutlery steel w/no hard carbides: ~600-800 Knoop
Novaculite (Arkansas stones): ~825 Knoop
Chromium carbide (D2, ZDP-189 are very heavy in it): ~1300 Knoop
Tungsten carbide (carbide pull-through sharpeners, also found in some cutlery steels): ~1400 Knoop
Aluminum oxide ('corundum' or 'Alumina'; Norton 'India' stones, and most ceramics of alumina): ~2100 Knoop
Silicon carbide ('carborundum'; Norton 'Crystolon' stones, wet/dry sandpaper): ~2600 Knoop
Vanadium carbide (significant in S30V/90V/110V steels and many others like them): ~2800 Knoop
CBN ('Cubic Boron Nitride'): ~4500 Knoop
Diamond: 7000 Knoop


David

Where would ceramic sharpening media, such as the sharpmaker rods, fall in this lineup?

 

[Jason B.]

They are Alumina ceramics so... Aluminum oxide.

 

[Obsessed with Edges]

Where would ceramic sharpening media, such as the sharpmaker rods, fall in this lineup?

Jason beat me to it. As he mentioned, they're aluminum oxide (usually called 'alumina' when used in ceramics), at approximately 2100 Knoop.


David

 

[HeavyHanded]

They do have additional quality as they are more than hard enough, binder wise, to produce a burnishing effect. This will be minimal on a dulled knife of high VC, but on a sharpened one they will refine it a bit more if used carefully.

 

[Ankerson]

They are Alumina ceramics so... Aluminum oxide.

There are different grades of Ceramics, I believe the Spyderco Whites are proprietary, not sure about the browns, but the Whites are extremely hard.

 

[ejames13]

There are different grades of Ceramics, I believe the Spyderco Whites are proprietary, not sure about the browns, but the Whites are extremely hard.

Interesting. I wonder if the high Vanadium steels suffer carbide tear out from the browns or whites...

 

[Obsessed with Edges]

All of the Spyderco ceramics are made using the exact same alumina abrasive grit (per Sal's own description), with binders, firing and surface finishing making the difference in rated grit performance. Therefore, they're all still limited by the hardness of the alumina itself, peaking basically around that ~2100 Knoop value, which is about as hard as alumina gets in any form (give or take an insignificant variance, as compared to silicon carbide and other abrasives used for sharpening). The white Spyderco hones are sintered, which I assume makes the hone denser than the brown/grey, which uses a binder of some sort.

Other 'ceramics' sometimes make use of different abrasive media, like silicon carbide or tungsten carbide. So, not all 'ceramics' will be of alumina, like Spyderco's are.


David

 

[Ankerson]

All of the Spyderco ceramics are made using the exact same alumina abrasive grit (per Sal's own description), with binders, firing and surface finishing making the difference in rated grit performance. Therefore, they're all still limited by the hardness of the alumina itself, peaking basically around that ~2100 Knoop value, which is about as hard as alumina gets in any form (give or take an insignificant variance, as compared to silicon carbide and other abrasives used for sharpening). The white Spyderco hones are sintered, which I assume makes the hone denser than the brown/grey, which uses a binder of some sort.

Other 'ceramics' sometimes make use of different abrasive media, like silicon carbide or tungsten carbide. So, not all 'ceramics' will be of alumina, like Spyderco's are.


David

They are proprietary, made for Spyderco so we will never know what they really are.

Ceramics get very complicated very quickly, exact composition, quality etc will make a huge difference.

Found a lot out when I was researching for a project I was working on awhile back.

 

[HeavyHanded]

Interesting. I wonder if the high Vanadium steels suffer carbide tear out from the browns or whites...

This is a pic of HSS withTungsten carbides on a Spyderco UF, I cannot imagine the Vanadium carbides would react any different. The pic was taken by BF member Ekretz and posted on this thread, there are a number of other pics as well, he did a great job on them.

http://www.bladeforums.com/forums/s.../page3?highlight=stropping+high+carbide+steel

 

[Obsessed with Edges]

Sal Glesser has long ago publicly said what they do for their hones, all of which are marketed as alumina ceramics, so we know what material they're starting with. The quotes below describe how they achieve the differences in grit ratings, between the medium, fine and uf hones (as quoted on their own forum, as far back as 2007):

"All of the ceramics use the same micron size (15-25). the different grits are created by different carriers, different firing techniques and diamond surface grinding.

sal

and:

"
Our gray stone is "medium". (Same material as fine but different carriers and heat treat).

Our fine stone is fine.

Our extra fine is a surface ground fine.



sal

David

 

[Ankerson]

Sal Glesser has long ago publicly said what they do for their hones, all of which are marketed as alumina ceramics, so we know what material they're starting with. The quotes below describe how they achieve the differences in grit ratings, between the medium, fine and uf hones (as quoted on their own forum, as far back as 2007):



and:




David

That's just the bare basics, it's a lot more complicated than that.

 

[Obsessed with Edges]

That's just the bare basics, it's a lot more complicated than that.

I don't doubt that; in fact, I fully agree. But I've never seen or heard of an alumina ceramic going significantly harder than about 2100 Knoop, no matter what process was used. Lots of differences in toughness, friability, grit shape, etc brought by different processes, but not so much significant difference in hardness, at least enough to rank it differently on the hardness scale among commonly used sharpening abrasives (vs. SiC, CBN, diamond, etc).


David

 

[ejames13]

This is a pic of HSS withTungsten carbides on a Spyderco UF, I cannot imagine the Vanadium carbides would react any different. The pic was taken by BF member Ekretz and posted on this thread, there are a number of other pics as well, he did a great job on them.

http://www.bladeforums.com/forums/s.../page3?highlight=stropping+high+carbide+steel

Thanks for that. Maybe I would get better results with some of my HSS blades coming straight off the diamonds and not taking them to the ceramics at all.

 

[Jason B.]

Ceramics have a factor called density, they are extremely dense and this has an effect on the sharpening. Yes, they are very hard but the density is a bigger player in the game. Regardless, this does not change their limitation while sharpening high alloy steels... It's still aluminum oxide.

 

[Herlock]

'Super steels' wouldn't be 'super steels' without the carbides that make them so. The carbides in super steels are WAY, WAY harder than Mohs 7-7.5; more like Mohs 9+, in the case of vanadium-heavy steels (30V, 90V, 110V, etc). Natural stones of any kind won't touch that, as they're nowhere near hard enough to abrade those carbides, and therefore will stop working as the carbides get in the way at finer grit levels. Even at very coarse grit, lesser abrasives won't cut or shape the carbides and will instead just scoop them out of the matrix steel, limiting how refined the edge can be made. At finer grit, the less-hard abrasive is no longer big enough to dig down between the carbides, which means it only 'skates' across the carbides without cutting them, and effectively stops working.
...
David

Hi. Thanks! Yes, this explanation very much mirrors my hands-on experience (as hobbyist and not a great sharpener ), at least with Niolox and M390 and not only for "natural" stones. I had this very same experience with Lansky stones. About S30V I have a different experience though. I can "easily" sharpen it with the Lansky stones.

 

[RatbikeJim]

Of all the steels I've sharpened D2 pissed me off the most. Hard to get shaving and didn't stay shaving sharp for long. Convex ed it by hand and it still lost its razor edge quickly, kept a working edge fine but I needed that razor edge for cleanly cutting filters at work to fit.

Ended up selling that knife (adamas). Got a code 4 in ctsxhp and much happier.

 

[Jamesh Bond]

This thread.

It's existence PERFECTLY illustrates why I personally find the obsession with super steels to be absolutely retarded. If it's enough of a bitch to sharpen that it requires combining highly specialized equipment, knowledge, and an Internet forum, then it might not be so super.

Super duper edge holding really does have diminishing returns.

I tend to balk when someone says their knife hasn't needed to be sharpened yet. Depends on your personal definition. Some people I know call their knife "really sharp" then proceed to heavily saw on their piece of string to sever it. I consider mine really sharp when they'll pop hair and go through phone book paper without resistance. Still others won't consider a knife sharp until it can literally whittle hair.

Frankly tho, even my own personal standard is truly stupid. No knife in any steel will keep that level of sharpness beyond a few pieces of cardboard. My s30v really doesn't impress me much over my 8Cr13Mov. It may stay hair popping an extra five minutes longer, but after that, they both cut the same. Once they're at the point where they're really pissing me off, it takes 2 minutes to bring back the "crap" steel and 20 for the "premium"

Diminishing returns.

The claims and tests and all really don't show a ginormous difference between low-mid and premium steel performance anyway. Not as huge as the hype suggests.

Despite my tone (insomnia), this isn't an attack on anyone. Simply a rant on something I can't wrap my head around.

I'mma get burned for posting this here.

 

[David Martin]

Yes, they have their opinions here but you have a good point as well. DM

 

[HeavyHanded]

This thread.

It's existence PERFECTLY illustrates why I personally find the obsession with super steels to be absolutely retarded. If it's enough of a bitch to sharpen that it requires combining highly specialized equipment, knowledge, and an Internet forum, then it might not be so super.

Super duper edge holding really does have diminishing returns.

I tend to balk when someone says their knife hasn't needed to be sharpened yet. Depends on your personal definition. Some people I know call their knife "really sharp" then proceed to heavily saw on their piece of string to sever it. I consider mine really sharp when they'll pop hair and go through phone book paper without resistance. Still others won't consider a knife sharp until it can literally whittle hair.

Frankly tho, even personal standard is truly stupid. No knife in any steel will keep that level of sharpness beyond a few pieces of cardboard. My s30v really doesn't impress me much over my 8Cr13Mov. It may stay hair popping an extra five minutes longer, but after that, they both cut the same. Once they're at the point where they're really pissing me off, it takes 2 minutes to bring back the "crap" steel and 20 for the "premium"

Diminishing returns.

The claims and tests and all really don't show a ginormous difference between low-mid and premium steel performance anyway. Not as huge as the hype suggests.

Despite my tone (insomnia), this isn't an attack on anyone. Simply a rant on something I can't wrap my head around.

I'mma get burned for posting this here.

Personally I'm with you 95%.

I've seen some of Ankerson's testing numbers and some of my own limited testing indicates potential multiples of "passes" before notable dulling on a standard cutting media. There's no doubt in my mind that some steels hold a functional edge for a looong time (D2 for example) and that factor is a function of the carbide content, whatever it happens to be.

However the steels that perform so, all seem to have idiosyncrasies in the type of finish they prefer, edge angle, certainly the type of abrasive used.

Whereas stuff like carbon steel at 1070 or higher, or fine grained stainless all take pretty much whatever edge finish you care to apply, and hold it for...a few - as in 'long enough' that re-sharpening isn't a hassle and I don't have to sweat it if the edge turns on something my edge shouldn't have slammed into. Its far easier to me to just have easy means of keeping my edges sharp rather than rely on inherent and pricey qualities of the steel itself. Truth be told I no longer even bring sharpening media with me when camping/backpacking as all my choppers and camp knives are low carbide stainless or carbon steel and can be touched up with improvised means right back to shaving sharp.

Not to mention the super steels all have a super duper price tag...they are pretty neat though, and that's the 5% I like about them. Several hundred passes through manila rope and still shave arm hair and slice thin paper - my regular cutlery can't touch that and the really cheap stuff can only dream about that level of edge retention.

 

[pathwinder14]

'Super steels' wouldn't be 'super steels' without the carbides that make them so. The carbides in super steels are WAY, WAY harder than Mohs 7-7.5; more like Mohs 9+, in the case of vanadium-heavy steels (30V, 90V, 110V, etc). Natural stones of any kind won't touch that, as they're nowhere near hard enough to abrade those carbides, and therefore will stop working as the carbides get in the way at finer grit levels...

I see your point. If that is the case, as the "soft" steel surrounding the carbides is abraded away by the stone, won't it remove those carbides and expose new ones? Isn't this effectively sharpening the blade?