Ranking of Steels by how sharp they can get?

mlmcasual

mlmcasual

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Jun 10, 2013
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Is there a ranking of steels based on their potential sharpness, assuming all other factors are equal?

I've upgraded to Shapton Pro whetstones (320, 1000, 2000, 5000) and use a 1-micron green paste leather strop. I've sharpened various knives, including my Benchmade Griptilian with CPM 20CV steel, to a mirror-polished, scalpel-sharp edge. I define "scalpel sharp" as the ability to fully dry shave single pass without tugging or feeling the hairs being cut.

However, I can't achieve the same sharpness with my KastKing Fillet knife made of G4116 German steel, despite it having a thinner blade and a 10-degree edge. It has a smooth edge and can cut some hairs, but i can't stone it as sharp as my 20CV, or M4, or 154 steel blades.

Is this a limitation of the softer G4116 steel? Can it not achieve the same level of sharpness as harder steels like 20CV?
 
In my experience every decent knife steel can get just as sharp although I don't have a BESS tester or anything. I find it often comes down to dealing with the burr properly. Some steels are easier than others to deburr fully. Obviously if the heat treatment is bad then that's a whole other story but I don't think that is as common as some people make out.

The other thing is getting a crisp apex on a fillet knife can be a bit challenging sometimes due to the flexibility of the blade. If you are confident you have a nice apex and have deburred then maybe a little work on a strop may clean up the edge and get better results. I don't have any issues getting a very sharp edge on my 4116 kitchen knives.

Edit: sorry, I missed the part about you already using a strop...
 
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Probably plain carbon steel ran at a higher HRC, above 60 or so. The simple carbon high purity steels like white no 1 and 2 rock my world.
 
I think all steels can get equally sharp, although some are easier to sharpen and some require different techniques and equipment to reach a high level of sharpness.

How would the CATRA tests work if every steel started out at a different level of sharpness?
 
I bought some scalpels out of curiosity. They tested in the BESS 150-200 range. Some production folding knives are better than BESS 100 out of the box. The double-edged razor blades I have tested ranged BESS 40-65. So "scalpel sharp" really isn't very sharp.

A particular knife might be very difficult to get sharp, but that is likely to be a matter of heat treatment or a burned edge rather than the type of steel, or perhaps an extremely stubborn burr.

There are types of steel that were never intended to be used in knives. Whether they can "take a keen edge" I cannot says since I am not a metallurgist,
 
mlmcasual said:
Is this a limitation of the softer G4116 steel? Can it not achieve the same level of sharpness as harder steels like 20CV?
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Not in any lasting way, not at a 10 degree angle. The steel probably can't hold a sharp edge at that angle without crumbling. With that geometry, you might not notice much cutting food, but shaving without tugging is a different story.
 
In my experience simple carbon steels take a finer edge than stainless steels. I have gathered this very unscientific evidence through the sharpening of at least 20 different steels (not counting vintage mystery steels) and shaving with straight razors for several years. Not to say that stainless steel can’t get VERY sharp- but I haven’t been able to get an edge I would call “shaveable”. Out of the stainless steels I have sharpened I think that cpm154 and s35 can get the finest edges.
 
If you have the correct abrasive(for a given steel's composition) and technique, they all can get VERY sharp, assuming the heat treatment is good.
 
Update,
Thanks to all the comments here, I thought it must be my technique and not the steel....
I don't think I achieved a proper burr during the sharpening... if you don't achieve a proper burr, it will never get truly sharp.

So, I went back to my 1000 shapton and did a much more aggressive sharpening, again at about 10deg.
and kept going till I cold feel a burr (the burr on this thin blade/angle is very hard to feel).. I then continued
to the other side and then ran the edge a very light 30 degree angle and also against wood to deburr it.
then went to a 2000, then a 5000 polish, and then my strop.. NOW, yes.. happy to report I have a stupid sharp hair popping edge.

It's interesting, I had recently sharpened a dozen knives ranging from folders, to kitchen knives and this was the first time I had "failed" and had to go back.
it's a learning experience.

How do you all test for sharpness without a machine? there is a million things I can do with paper but IMO all paper test only test for eveness and general sharpness
the only thing I have been able to come up with is dry shaving arm hairs.

also, would a 12,000 shapton benefit me to get things even sharper? as it is with my 5000 and 1micron green strop I can get hair popping mirror edge.
 
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mlmcasual said:
.. if you don't achieve a proper burr, it will never get truly sharp.
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Not entirely true.
Cliff Stamp could sharpen a knife withour raising a burr.

mlmcasual said:
would a 12,000 shapton benefit me to get things even sharper?
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So, how much sharper do you want your knives to be?
To cut yourself remotely standing two or three yards from the blade?

About green compound... if you're referring to standard green polishing compound....
I wrote to the company who makes those compounds and I recieved the answer....
basic particles in this compound form a clusters of the size up to 40 microns.
 
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I think having a very fine grain structure is important for achieving the sharpest possible edge. I believe 14c28n was specifically developed for razors. That said, I’ve yet to encounter a properly heat treated blade that couldn’t be brought to shaving sharp.
 
For eyeball surgery, doctors use obsidian scalpels (made of volcanic glass). I suspect the harder the material is, the finer an edge (i.e., narrower bevel angle) you can put on it and still have the material hang together at the apex ... which will equate to "sharper" ... the problem is that it may not have much wear resistance or toughness.

Seems to me the densest material, in terms of how tightly packed the atoms or molecules are, is diamond, which is one reason why it's so thermally conductive. It's not very tough, since you can smash a diamond fairly easily with a small hammer, but I suspect you could get it dam sharp. Anyone know anything about this? Does anyone make diamond knives, like for microtomes or something like that?
 
Blade Lab said:
No, he could sharpen a knife without raising a burr large enough to detect with a finger.
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In one of his videos I watched he explained he sharpens from both sides to the point the edge just stops reflecting light. According to his words this way the edge is still flat and about 10 microns wide.
Then he did the micro bevel. I assumed he knew what he was doing.
 
Back to the topic…

A few days ago I was trying to sharpen my fathers SAK Hiker. According to all the info I could find the steel suppose to be 4112 at about 55-56HRc. But I didn't take it to work to measure the hardness.
Anyway; no matter what I did I couldn't remove a burr no matter what I did. Like fighting rubber or chewing gum. Damn thing didn't want to cut news print cross fibers.
Otherwise I have no problem sharpening all my other knives from old Inox kitchen knives to all my 12c27 Opinels and D2 EDC knives.
I can even sharpen my cheap eBay Browning ''tactical'' EDC knife which measures 50.1HRc.

By the way; just for fun I tried to make my Opinel No8 Inox to whittle hairs. I couldn't. No matter what I did it just cuts through hair.
How to sharpen just enough to whittle hair but not to cut the hair?
 
TheOne45 said:
In one of his videos I watched he explained he sharpens from both sides to the point the edge just stops reflecting light. According to his words this way the edge is still flat and about 10 microns wide.
Then he did the micro bevel. I assumed he knew what he was doing.
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I find this extremely unlikely. For one thing he would have needed to use at least a laboratory grade optical microscope or something better to be able to confirm that sort of size, otherwise he is just speculating. He would also have to be very accurate on when to stop the initial grinding to get to an apex that is at that scale but not creating a burr by mistake, not to mention that whether or not he formed a small burr at this stage is completely arbitrary if he is then applying a micro-bevel. Also he would need to start with a very uniform apex to even make this theory possible otherwise he would end up with any existing edge damage that is deeper than the subsequent micro bevel remaining and having an inconsistent apex at the end of the sharpening session.

I think a lot of the time what people think is happening is not always what is actually happening in reality. I don't think it is a bad idea to aim at not creating a burr if you are just doing a minor touch up or only creating a small burr and switching sides more often for a normal sharpening.

The other thing is a burr is not that scary. Just learn good technique to remove the burr and you are good to go.
 
chalby said:
I find this extremely unlikely. For one thing he would have needed to use at least a laboratory grade optical microscope or something better to be able to confirm that sort of size, otherwise he is just speculating. He would also have to be very accurate on when to stop the initial grinding to get to an apex that is at that scale but not creating a burr by mistake, not to mention that whether or not he formed a small burr at this stage is completely arbitrary if he is then applying a micro-bevel. Also he would need to start with a very uniform apex to even make this theory possible otherwise he would end up with any existing edge damage that is deeper than the subsequent micro bevel remaining and having an inconsistent apex at the end of the sharpening session.
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Well; that was his theory. I doubt he took his knife to some lab to get a SEM image of his edge to see, if this works in real life.
Still, 10 microns sounds scary but with other words this is 0.01 milimeters which is not so scary number in machining of metal.
Now bear with me;
let's say this approach is possible at least on some parts of the edge. I would say the edge still reflects light if it's about 0.02 milimeters or so (20 microns) wide. Theoretically you could take your time and carefully grind and observe the edge under the loupe with light and get it to the point it just barely reflects light. Then very gentle stroke or two till it just stops reflecting and then you do micro bevel.
I personally don't see a point in that but someone else might.
chalby said:
I think a lot of the time what people think is happening is not always what is actually happening in reality.
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Agree on that.
I'm advocating ''do something and then inspect'' approach when you learn to sharpen - sharpen an observe the edge under high magnification to see, what you are doing. That's how you learn. That's why I sometimes took my knife to work and observe the edge under the microscope.

chalby said:
I don't think it is a bad idea to aim at not creating a burr if you are just doing a minor touch up or only creating a small burr and switching sides more often for a normal sharpening.
The other thing is a burr is not that scary. Just learn good technique to remove the burr and you are good to go.
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Agree on that too.
I usually just sharpen with #240 or #320 diamond stone till I get a burr and then I strop and that's it.
 
TheOne45 said:
Still, 10 microns sounds scary but with other words this is 0.01 milimeters which is not so scary number in machining of metal.
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It is not an apples to apples comparison as he was flat-lapping a chunk of metal rather than cutting a bevel, but Todd Simpson tested material removal rate of some common sharpening abrasives. At the rates he achieved removing ten microns of material would take hundreds of strokes. One can expect the higher pressure in bevel cutting to be faster, but the idea of "sneaking up" on a nascent apex is not really far fetched.

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I'm not saying it's not possible or even far fetched, just not sure what the point is of going to that much trouble to avoid a burr. Just seems unnecessary, but each to their own. If that approach works for you then I would say stick to it.
 
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