View Full Version : sharpness vs. keenness

07-30-2012, 06:09 PM
With knives I see a lot of misuse of some terms.

On a properly sharpened knife, the edge under magnification will measure ~.4 microns across. (diameter) The edge of a knife will start to feel dull when it wears to ~1 micron in diameter.

Sharpness is the measurement across the edge.

Keenness is how fine the scratch pattern is on the sharpening bevel.

Over sharpening is when the knife starts to become duller from incorect sharpening or too much stropping. If a little is good, a whole bunch is not better.

Dullness is when an edge, because of wear, is greater than 1 micron.

Knives can dull because of abrasive wear, adhesive wear, or corrosive wear.


07-30-2012, 06:15 PM
TK hand one of your gyutos at the west coast get together. It was the only knife I wanted to keep picking up. You do amazing work.

07-31-2012, 03:06 AM
I think I am a culprit of this. I have noticed when stropping and not paying attention to what I am doing, like watching video, reading a forum, ect. I will notice some times that it feels worse. Never knew there was a keenness to compare to sharpness.

07-31-2012, 09:25 AM
Devin, I read this post this morning and have been thinking about on and off all day.

I know that you've stated in the past that you think that many knife nuts over-sharpen their knives, in that regard you mean that their knives are overly 'keen', which leads to knives dulling faster.

If sharpness is a quality of an edge determined by the width of the edge - substantially less than one micron - then surely it must benefit knives for them to be abraded with particles of one micron or less. i.e 8000+ grit stones. When in the past you have said that most knife nuts over sharpen, do you mean that they take their stone progression too far for the knives, or they spend too much time on each stone?

I'm not disagreeing with you here, after reading some of your comments about over-sharpening, I've been aiming at far more aggressive edges for gyutos and petties with great results.

Can you also talk about the difference between 'abrasive wear' and 'adhesive wear'?

I'm curios about this, because of the idea that if you know how a certain knife will be used, different sharpening styles and techniques can affect performance. i.e slicing knives made of steel with large carbides will perform better with a less refined edge. Can that concept also be extended to edge retention? for example if I have a knife that will be used for certain tasks - push cutting veg and that's about it, is there an ideal balance of sharpness and keenness that will extend time between sharpenings?

I'm going to go and sharpen a knife now.

07-31-2012, 11:38 PM
TK hand one of your gyutos at the west coast get together. It was the only knife I wanted to keep picking up. You do amazing work.

+1. That and El Pescador's conversation about Hoss' knives. Moved Devin's knives WAY up on the list of lust-objects!