What steels take an extremely fine edge?

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Cliff Stamp
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Re: What steels take an extremely fine edge?

#21

Post by Cliff Stamp »

KevinOubre wrote: Cliff, wouldn't this apply to mostly coarse grits?
The rate of polish or cutting is influenced by the particle size. As the abrasive gets much larger than the size of the carbides it starts to "see" them even less. However the carbide volume compared to the steel volume is small even in steels like 10V. This is a k390 blade sharpened with a Soft Arkansas stone which easily cuts a polished micro-bevel even though the stone is only quartz. That stone leaves a polish so high is starts catching hair and shaving above the skin.

https://youtu.be/iJw3fFp54_M
I have not had great results getting a polished, mirror edge using the spyderco stones on steels like 10V, S90V, and S110V.
What happens exactly? There are a gajillion reasons why that can be happening, the most common one is that due to the very high grindability the edge isn't prepared for the micro-bevel or if you are polishing the edge vs sharpening (apex bevel) then you can't skip grits with poor grindability.
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Re: What steels take an extremely fine edge?

#22

Post by sbaker345 »

You could also be pressing too hard, Ive noticed to get an extremely sharp polished edge with s30v you need a VERY light touch, id imagine s90v would be even more so. 3lbs of force is way too much to finish the edge with
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Re: What steels take an extremely fine edge?

#23

Post by KevinOubre »

Cliff Stamp wrote:
KevinOubre wrote: Cliff, wouldn't this apply to mostly coarse grits?
The rate of polish or cutting is influenced by the particle size. As the abrasive gets much larger than the size of the carbides it starts to "see" them even less. However the carbide volume compared to the steel volume is small even in steels like 10V. This is a k390 blade sharpened with a Soft Arkansas stone which easily cuts a polished micro-bevel even though the stone is only quartz. That stone leaves a polish so high is starts catching hair and shaving above the skin.

https://youtu.be/iJw3fFp54_M
I have not had great results getting a polished, mirror edge using the spyderco stones on steels like 10V, S90V, and S110V.
What happens exactly? There are a gajillion reasons why that can be happening, the most common one is that due to the very high grindability the edge isn't prepared for the micro-bevel or if you are polishing the edge vs sharpening (apex bevel) then you can't skip grits with poor grindability.

The sharpening regiment is that I start with a coarse diamond stone to shape if it needs it after I have cut the apex off. Then after I get that grit finish on the edge, I move to a fine diamond stone until I get that scratch pattern, then similar for a medium spyderco stone, fine spyderco stone, then ultra fine spyderco stone. I have started to use a similar method to Joe Calton where he raises a burr, weakens it, then cuts it off with a micro bevel. I usually put the micro bevel on at the last stage. I have been practicing the plateau method you use but for some reason I cant figure out haven't gotten great results. Still working on it. The edge just feels distressed after I am done sharpening if I take it to a high polish, but its only for really high carbide steels. I have no issues with ZDP-189, M4, D2, 154CM, S30V, 1095, O1, 440C, 12C27, ELMAX, etc. I find that I can get 10V, S90V, and S110V the sharpest at the fine diamond stage but if I go past that, I begin to see poorer edge performance than the lower grits, as in the apex is very instable relative to the lower grits and doesn't reach a high sharpness. They wont even cut paper the well.
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Re: What steels take an extremely fine edge?

#24

Post by Cliff Stamp »

KevinOubre wrote: The sharpening regiment is that I start with a coarse diamond stone to shape if it needs it after I have cut the apex off. Then after I get that grit finish on the edge, I move to a fine diamond stone until I get that scratch pattern, then similar for a medium spyderco stone, fine spyderco stone, then ultra fine spyderco stone.
Kevin,

What that is a common type of progression it is one of the hardest ones to use because of the tendency to form a burr and fatigue the edge. There is no slurry to minimize the burr formation and the repeated over lap of solid ceramic abrasives which tend to burnish vs abrade makes getting a low fatigued apex difficult. If the steel is easy to grind these effects are reduced. I would suggest a much simpler process :

-use the coarse diamond to reset the edge
-use a King 1000 or similar to polish the edge, but more importantly the heavy slurry will tend to minimize any burr
-apex on the Fine, finish with very light passes, 5-10 grams

In regards to the burr, if you do anything to break it off or similar methods you are going to damage the steel beyond what is broken off and this again is going to make setting that high polish at the apex difficult. With easy to grind/sharpen steels this likely won't be noticed, but with harder to grind/sharpen steels the effects are more noticeable.
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Blerv
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Re: What steels take an extremely fine edge?

#25

Post by Blerv »

Chemistry aside, thin steels take sharp edges quite easily. Mainly because...well, they are quite thin. :)

I have a lot of love for carbon blades and even more for steels like Superblue. My regrinds are my favorite functional knives though. From ZDP-189 to VG-10 and Cobalt Special, they are all insanely sharp for lighter cutting tasks.
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Re: What steels take an extremely fine edge?

#26

Post by Cliff Stamp »

Blerv wrote:Chemistry aside, thin steels take sharp edges quite easily. Mainly because...well, they are quite thin.
That is a confusion of sharpness for cutting ability. The simplest way to understand the difference is to think about modifications to the handle which would make it more comfortable, secure and easier to control. If the handle isn't slipping, if the grip has low fatigue, if it fits well and you can put force easily into the blade - all of these increase the cutting ability however no one would confuse that and say that the blade was being "sharpened" by modifications to the handle. In the same way a regrind doesn't make the blade sharper, it does the same thing as the modifications to the handle, it increases the cutting ability.
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Re: What steels take an extremely fine edge?

#27

Post by Surfingringo »

Cliff Stamp wrote:
Blerv wrote:Chemistry aside, thin steels take sharp edges quite easily. Mainly because...well, they are quite thin.
That is a confusion of sharpness for cutting ability. The simplest way to understand the difference is to think about modifications to the handle which would make it more comfortable, secure and easier to control. If the handle isn't slipping, if the grip has low fatigue, if it fits well and you can put force easily into the blade - all of these increase the cutting ability however no one would confuse that and say that the blade was being "sharpened" by modifications to the handle. In the same way a regrind doesn't make the blade sharper, it does the same thing as the modifications to the handle, it increases the cutting ability.
I think maybe his point was not that a thin blade will inherently reach a higher level of sharpness but that it will reach a high level of sharpness more easily because of the much smaller amount of metal that needs to be removed.
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Re: What steels take an extremely fine edge?

#28

Post by levs18 »

Awesome thread! How do you experts feel the upcoming HAP-40 will perform in this regard?
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Blerv
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Re: What steels take an extremely fine edge?

#29

Post by Blerv »

Surfingringo wrote:
Cliff Stamp wrote:
Blerv wrote:Chemistry aside, thin steels take sharp edges quite easily. Mainly because...well, they are quite thin.
That is a confusion of sharpness for cutting ability. The simplest way to understand the difference is to think about modifications to the handle which would make it more comfortable, secure and easier to control. If the handle isn't slipping, if the grip has low fatigue, if it fits well and you can put force easily into the blade - all of these increase the cutting ability however no one would confuse that and say that the blade was being "sharpened" by modifications to the handle. In the same way a regrind doesn't make the blade sharper, it does the same thing as the modifications to the handle, it increases the cutting ability.
I think maybe his point was not that a thin blade will inherently reach a higher level of sharpness but that it will reach a high level of sharpness more easily because of the much smaller amount of metal that needs to be removed.
That was certainly part of my point, thank you :). Regrinds are much easier sharpen with the lack of shoulder material.

Still (Cliff), I'm confused why if a knife is reground beyond factory specs it would not be "sharper". Angle is typically reduced, material behind the edge is removed, force needed per cut decreases (even if you are simply pushing material against the stationary knife. Sure it's a lazy/layman answer to "What steels take an extremely fine edge?" but it's a fairly pragmatic one given the results. Assuming of course we aren't talking about edge durability or polished/fine vs coarse and all that stuff.
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Re: What steels take an extremely fine edge?

#30

Post by spyderg »

I've think I've got nice variety of steels in my, small compared to many on here, collection. VG10, S30V, S35VN, ZDP 189, CTSXHP, CTSBD1, D2, 1095, 440C, 110V, 10V, Superblue, and I'm sure I'm forgetting some and not bothering with some "cheaper" ones. But as far as easiest to put a great edge on, CPM Cru-wear in my Manix2 has got to be the best.
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Re: What steels take an extremely fine edge?

#31

Post by Cliff Stamp »

levs18 wrote:.... upcoming HAP-40 will perform in this regard?
HAP-40 is a HSS so the apex stability is second only to steels which are general razor blade steels like W1, White, AEB-L, etc. . The main issue with those steels like HAP-40 is the low grindability so while the apex stability is high unless you have decent stones you might find it hard to sharpen because of problems in grinding it. With those steels is it very easy to push metal around vs cutting it which can lead to problems with burr formation and fatigue at the apex.
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Re: What steels take an extremely fine edge?

#32

Post by Cliff Stamp »

Blerv wrote:
[...]
if a knife is reground beyond factory specs it would not be "sharper".
Because that definition of sharpness is problematic it would result in handle modifications such as I noted also being classified as sharpening but it is obvious that isn't the case. Would you argue that if I modified the handle to give it better control/security it would be sharpening? It is likely you could not but it can easily result in less force in the cut, even dramatically so.

Defining words, even when we know what they mean is very problematic as that isn't how our brains work. We understand what things are by assembling a pattern from a group of events and then finding the common pattern. Most people can answer these questions almost instantly but would struggle with a definition of sharpness which could be applied by someone who didn't understand it to answer them. Which of the following is an example of sharpening :

-adding a fuller to the blade
-changing a satin finish to a full mirror polish on the blade flats
-adjust the blade to handle angle
-add a pommel weight
-remove a burr from an over ground edge

If you ask most people, even people not into knives they will likely answer almost immediately that the first four are not sharpening but they will influence the cutting ability. People who sharpen knives will immediately say of course the last one is a part of sharpening but why is it when all of them influence cutting ability? It is because sharpness is that which is a property of the apex itself. Again most people know that is what it means but will struggle to put it into words.

But it isn't just an issue with sharpness, ask anyone to define "game". It is very likely no matter how much they try to define it you can think on something which they would accept as a game which isn't in their definition or something which does fit their definition but isn't a game.
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Re: What steels take an extremely fine edge?

#33

Post by Nate »

To take confusion on terms a bit further, I am still a bit lost in this thread.

I read the OP as essentially asking the old "what steel gets the sharpest" question. Aside from the problem of what kind of sharp, (slicing/push-cutting?,) I thought what Jim and Lance were saying was essentially correct; that maximum attainable sharpness was dependent on the skill of the sharpener, not the steel.

So when apex stability was brought up as the materials property that defines an "extremely fine edge" I became a little confused about how it relates. I had been thinking that apex stability primarily dealt with the steel's ability to hold a high sharpness and to some extent remain durable at low edge angles and thin cross sections, but now it seems like there may be some gaps or misconceptions in the way I had it framed.

Hope this post didn't make everyone dumber :) Any clarification would be appreciated.
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Re: What steels take an extremely fine edge?

#34

Post by Cliff Stamp »

Nate wrote:[...] that maximum attainable sharpness was dependent on the skill of the sharpener, not the steel...
If you want to argue the theoretical limit is the same then there would be merit to it, however practically the apex stability has a very strong limit on what can be achieved. As a point of reference, for high apex stability steels, Landes noted you should be able to lay a grape on a table and cut it with the knife without moving the grape. Trying to achieve that level of sharpness with steels which have low apex stability :

-coarse grain structure
-large aggregated carbides
-lots of retained austenite/pearlite
-low martensite hardness
-quench cracking

and similar will be so difficult so as to be impossible. Can it be done in theory, sure, but in practice not really. Take a hair, bring it down on the edge of the knife and have the hair be cut in half without actually bending, that kind of sharpness is very difficult to achieve with low apex stability steels. But the more "normal" type sharpness :

-shaving arm hair
-slicing fine papers

can be achieved with pretty much anything, even unhardened mild steel.
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Re: What steels take an extremely fine edge?

#35

Post by Bill1170 »

These semantic problems can be a real barrier to deeper understanding, so it is worthwhile to make some effort to define terms so we are talking about the same things.

It seems to me that both the original poster and Cliff mean the same thing by sharpness, namely how minuscule a mesa or flat place can be attained at the very apex of the edge. Once you reach extreme sharpness, the grain size of the steel becomes an issue. Obviously, smaller grain structured steels have a higher theoretical possible sharpness than coarser grained steels.

Similarly, Cliff is correct to draw a distinction between sharpness and cutting ability. With identical blade shapes, steels, edge finish, and sharpnesses, a thinner knife will outcut a thicker one.

Questions of edge retention, damage resistance, and apex stability are all separate matters that we can set aside when evaluating ONLY sharpness. Of course, in real world cutlery there are all of these factors to take into consideration. There, the benefits of balanced geometry and balanced steel properties become very apparent.
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Re: What steels take an extremely fine edge?

#36

Post by Cliff Stamp »

Bill1170 wrote:... how minuscule a mesa or flat place can be attained at the very apex...
I think there are two aspects :

-the thickness of the apex
-the depth of any irregularities in the apex and the thickness of their sides

The difference comes out if you look at sharpness on a push vs a slice and especially edge retention on both.

It is often argued that the second point decreases sharpness and the ultimate sharpness is when the apex has no irregularities and has a minimum thickness (a highly polished edge). However if you look at sharpness on a draw then this isn't the case.
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Re: What steels take an extremely fine edge?

#37

Post by Bill1170 »

True. I was thinking of only push cutting sharpness to reduce matters to the greatest conceptual simplicity. It is my woodworking background coming to the fore.
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Re: What steels take an extremely fine edge?

#38

Post by JD Spydo »

Cliff Stamp wrote:
sbaker345 wrote:... vanadium carbides are supposedly harder than sharpmaker stones, Does that mean s90v and s110v would eat the stones and or not get sharpened extremely well?
The Sharpmaker rods are alumina which is softer than vanadium carbide however only a small part of the steel is vanadium carbide even in steels which are high carbide. Just think about using your hands to dig in the ground. Even though your fingers are softer than rocks you can still dig as the rocks are just moved out of the way. A similar thing happens when you grind into the knife, the vanadium carbides are just pushed out of the way. This is why you can even sharpen steels like 10V on Arkansas stones which are quartz which is softer still than alumina.
This is incredibly interesting Cliff>> this is the first time I've heard that any metal was harder than the alumina/ceramic stones that Spyderco uses. But I'm also guessing that maybe Tungsten carbide may also be harder as well?

I also find it interesting that you would make mention of novaculite/Arkansas stones because I had been told quite a long time ago that those stones are pretty much antiquated when sharpening these newer/better blade steels. I've still kept one of my Arkansas stones that I got from a guy who used to work for the people that made the Washita type of Arkansas stones. This stone I'm speaking of was called a "Blue-Black" stone. It's an extremely fine grit stone and it has great finishing properties. I'm now wondering how Coticules ( Belgium Razor stone) which is another natural stone compares?
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Re: What steels take an extremely fine edge?

#39

Post by Nate »

Thank you for the replies Cliff and Bill, very clear.
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Re: What steels take an extremely fine edge?

#40

Post by Ankerson »

Nate wrote:To take confusion on terms a bit further, I am still a bit lost in this thread.

I read the OP as essentially asking the old "what steel gets the sharpest" question. Aside from the problem of what kind of sharp, (slicing/push-cutting?,) I thought what Jim and Lance were saying was essentially correct; that maximum attainable sharpness was dependent on the skill of the sharpener, not the steel.
Technically it is correct because what I said about the actual apex thickness measured in nano meters is what sharpness really is.

The smaller that number is the sharper the edge will be, that can actually be measured, but it takes an electron microscope to do it.
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