How sharp to recognize difference in carbide size?

[bpeezer]

I frequently see people mention carbide size in reference to sharpness. I've seen people say things like "I won't carry a D2 blade because it can't get sharp enough for how I like my knives." I figure that's more likely their sharpening incompetence than anything else, but how sharp does a blade have to be before the carbide size keeps it from getting any sharper?

 

[Alberta Ed]

Good question. I suspect that steels with large amounts of very hard carbides, such as D2, S30V, VG-10, are more difficult to sharpen, and respond best to diamond hones. But that doesn't mean they won't take a very fine edge. Carbides are incredibly tiny, measured in millionths, compared to edge thickness. Hopefully a metallurgist can weigh in here.

 

[Cynic2701]

Hair whittling sharpness is achievable with D2 and other high carbide volume steels. The question is whether or not they hold that type of edge better, as well, or worse than a low alloy steel. Much discussion is had in the kitchen knife community over this.

Is there a theoretical limit to achievable sharpness? Yes, but I don't think that it matters nearly as much as people seem to think. As you mentioned, it likely is a difference in sharpening skill and technique or even equipment that would truly make the difference.

 

[Obsessed with Edges]

Even though carbides (chromium/vanadium) are very hard, abrasives like diamond are harder. Therefore it's possible (though not necessarily easy ) to abrade and shape the carbides with the appropriate abrasives. Sharpening D2 has taught me that it definitely takes more time to do it, but it can still get a lot sharper than the implied carbide size would seem to allow.

The tricky part is in being able to abrade the carbides at the edge without tearing them out of the surrounding softer matrix steel. To me, that means using very hard, but also very fine-grit abrasive appropriate for the steel, and going about it as gently as possible. This is why I'm convinced a lot of extra time is needed to get it there. That's how I've gone about refining my D2 blades; all of them have been a 'work in progress' for some time, and they keep getting sharper as long as I don't try to rush the process.

In comparing the cutting performance of the edge vs. how big the steel's carbides are said to be, I always think about what Crucible has spec'd for S30V's average vanadium carbide size (2-4 microns). It's been said that a true shaving edge needs to be sub-micron in thickness, maybe 0.5 micron or thinner. So, if one is routinely able to shave with a steel like S30V, or D2 with chromium carbides said to be much, much bigger, then I think it's safe to say it's possible to actually shape the carbides at the edge by abrasion, using the right tools and techniques.


David

 

[Jason B.]

It does not effect sharpness the way its so often said to.

 

[Chris "Anagarika"]

David,

Thanks for the insight. I should have known that, but never thought of it that way, because what people said kept me thinking that the carbide always got torn out of the matrix. You said that since diamond is harder, it should be able to abrade the carbide without tearing probided it's fine enough and using less pressure (obviously).

I just had a 'duh' and facepalm moment
Been having hard time doing S3V and earlier my 9Cr. I guess rushing it was the culprit o the chipping out apex as I've seen

 

[sodak]

Your initial guess about people was correct. Using carbide volume to excuse lousy sharpening is BS. Completely. I can get D2 and CPM 10V just as sharp as 1095, 5160, etc.

 

[L2bravo]

Even though carbides (chromium/vanadium) are very hard, abrasives like diamond are harder. Therefore it's possible (though not necessarily easy ) to abrade and shape the carbides with the appropriate abrasives. Sharpening D2 has taught me that it definitely takes more time to do it, but it can still get a lot sharper than the implied carbide size would seem to allow.

The tricky part is in being able to abrade the carbides at the edge without tearing them out of the surrounding softer matrix steel. To me, that means using very hard, but also very fine-grit abrasive appropriate for the steel, and going about it as gently as possible. This is why I'm convinced a lot of extra time is needed to get it there. That's how I've gone about refining my D2 blades; all of them have been a 'work in progress' for some time, and they keep getting sharper as long as I don't try to rush the process.

In comparing the cutting performance of the edge vs. how big the steel's carbides are said to be, I always think about what Crucible has spec'd for S30V's average vanadium carbide size (2-4 microns). It's been said that a true shaving edge needs to be sub-micron in thickness, maybe 0.5 micron or thinner. So, if one is routinely able to shave with a steel like S30V, or D2 with chromium carbides said to be much, much bigger, then I think it's safe to say it's possible to actually shape the carbides at the edge by abrasion, using the right tools and techniques.


David

David, you are one smart fella. Always great to read your responses. Thanks!

 

[Obsessed with Edges]

David, you are one smart fella. Always great to read your responses. Thanks!

Don't know about that. Thanks for your kind words, just the same. I do like threads and questions like this, because it does make me think in more detail about some things that I might otherwise have taken for granted, without fully understanding why.


David