Sharpness vs Cutting Ability

[Larrin]

New article on the definitions of sharpness and cutting ability, where I answer such questions as:

How is sharpness defined in the scientific literature?
Is sharpness better measured with its cutting behavior or by observing the edge?
Is a thinner edge automatically sharper than a thicker edge?

https://knifesteelnerds.com/2018/08/06/ ... g-ability/

[MichaelScott]

Another fine example of learning more and more about steel, “sharpness”, cutting and the edge. Fascinating. Thank you! I’ve bookmarked your site and plan to continue my knife-nerd post grad work there. I recommend everyone with any interest in the topic to read your article.

[JD Spydo]

Well Larrin you've again put up some very interesting information. I've just got to start surfing that website and I've been putting it on the back burner because I just have been extremely busy of late. I read about half of it but this evening I'm going to check out the main parts of that website.

I sure wish our good Brother Cliff Stamp were here to comment on all of this because he has a very good technical mind like yourself. I'm now wondering if they have done any test on serrations? I know each serration pattern would have it's own strengths and weaknesses. But it would be interesting to see which pattern holds up the best during demanding cutting jobs.

Edge retention has been a widely debated subject here and at BF as well and there sure are a lot of factors involved. Also I'm wondering if they did any separate tests on any of the nitrogen based blade steels?

[Larrin]

Well Larrin you've again put up some very interesting information. I've just got to start surfing that website and I've been putting it on the back burner because I just have been extremely busy of late. I read about half of it but this evening I'm going to check out the main parts of that website.

I sure wish our good Brother Cliff Stamp were here to comment on all of this because he has a very good technical mind like yourself. I'm now wondering if they have done any test on serrations? I know each serration pattern would have it's own strengths and weaknesses. But it would be interesting to see which pattern holds up the best during demanding cutting jobs.

Edge retention has been a widely debated subject here and at BF as well and there sure are a lot of factors involved. Also I'm wondering if they did any separate tests on any of the nitrogen based blade steels?

Serrations are a difficult one to compare with plan edges since they cut so differently. Spyderco's CATRA studies on serrated edges are probably the most extensive analysis, though I don't know to what degree those have been published.

The edge retention of nitrogen based steels will depend primarily on their hardness and the carbides/nitrides that are present. Vanax contains vanadium nitrides, Cronidur 30 has chromium nitrides and H1 as I understand it has little or no nitrides. For maximum slicing edge retention you want the greatest possible wear resistance which would mean a high fraction of the hardest possible carbides/nitrides.

[ChrisinHove]

Interesting stuff, again.

I like the differentiation between sharpness and cutting ability.

Coincidentally I was pondering that this morning using an old sabatier kitchen knife. I have recently overhauled it, sharpening out some damage, but also polished the blade to improve it cosmetically.

The high polish has actually made a very noticeable improvement in cutting through thick veg. and has me wondering why more blades aren’t supplied polished, also considering the additional corrosion inhibition.

[Surfingringo]

Good writeup Larrin.

I had a thought about this observation... "Interestingly, double bevel edges cut with less force at the same angle as the single bevel edges."

-I suspect that might be a result of greater friction on the blade face. Depending on the nature and elasticity of the material being cut, a double bevel edge can act as a wedge that pushes the material apart, causing the media to push against both sides of the blade with less force. A single bevel edge would have the full force and friction on one side of the blade and it would even be increased by the force created by the chisel edge pushing the blade the material. Not sure if that makes sense and even if it makes sense it may not be correct but it's my first hypothesis to account for the difference.

[Larrin]

Good writeup Larrin.

I had a thought about this observation... "Interestingly, double bevel edges cut with less force at the same angle as the single bevel edges."

-I suspect that might be a result of greater friction on the blade face. Depending on the nature and elasticity of the material being cut, a double bevel edge can act as a wedge that pushes the material apart, causing the media to push against both sides of the blade with less force. A single bevel edge would have the full force and friction on one side of the blade and it would even be increased by the force created by the chisel edge pushing the blade the material. Not sure if that makes sense and even if it makes sense it may not be correct but it's my first hypothesis to account for the difference.

I would definitely be interested if someone who is skilled in modeling could explore that one.