What is sharp?

Sean Cochran

Well-Known Member
There have been several threads lately about sharpening methods. So.....what exactly is sharp? Is it shaving, paper cutting?

I know different tasks require different edges, chopping, slicing etc. also different edge geometry and steel depending on the job required. But all other things being equal what kind of edge do you want?

I heard someone say once if a knife will cut what it is intended to cut it is sharp. I tend to agree with that. For instance, in an EDC I like a blade with a little "bite" to it. If Im cutting tomatos I want laser sharp.

What are your thoughts?
 
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Rasp181

Guest
I think every knife should be as sharp as you can get it. It's a fact that a sharp knife is safer than a dull one. Sharper means less force used to cut.
 

Mike Jones

Google Master
I like knives to be shaving sharp. If they have trouble slicing paper, they're in the sharpening pile. Having a sharp knife is safer, as Rasp stated. Having it very uniformly sharpened will keep a sharp edge better.
 

Steven Janik

SUPERMOD & AWARDS BOSS
I think the most recognized definition of sharp is "shaving sharp". It may not be correct for every blade, but when I hand some one a knife I always say "it's sharp" and undoubtedly they will try to shear their forearm. This doesn't work for serrated blades but that doesn't mean that they are not sharp in their own regard. Sharpness is a direct relationship between geometry, blade weight, grind angle and execution. A less then optimal blade will cut rope if drawn thru the rope at the same time pressure is applied, yet a straight razor won't do much when pressed against the same rope.

I cringe when I see the wrong mindset with a truly sharp knife as I have had two people seriously cut with knives I've sharpened. My knives are shipped at about 95% sharpness if such a thing could be calculated. My EDC is stropped and polished to scalpel sharpness, but I don't let anyone use it. S0... after all that, I guess sharpness is very subjective. What's everyone else think?

I have been involved in engineering studies on broadhead sharpness and optimal sharpness allows the blade to sever cellular and molecular structure rather than just push it aside. This is best achieved with maximum blade thickness of .100" or less.

Steve
 
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NJStricker

Well-Known Member
Sharpness is relative to what the tool was designed for. I can file my double bit axe until it is "sharp" and will make the wood chips fly. But I can't shave with it.
 

HELLGAP

Dealer - Purveyor
Steve is right just cuzz a blade shaves the hair off your arm doesnt mean its the sharpest . All that means is the blade is sharp enough to shave your arm hair would you try to shave you face with that same blade lmao go ahead and see what happens you will need stitches for sure. I have been perfecting my edges the last while and will be trying a leather belt for my grinder ,I will heat it up and melt the rouge into it and then try to hone at say 4 or 6 thousand. All the knives I sharpen will shave arm hair but only certain steels have the ability to hold a microscopic razor edge. Most steels can t do that the steel just isnt able to do that. I watched a guy 2 weeks ago who split a hair so I tried with my own knife convex edge cpm154 rc61 and I could not only split a hair but make pig tail curls. So I thought my knife was sharp then I went to you tube and watched a guy demonstrate his straight razor , he could litterally slice a single hair with the razor blade with out the hair even bending. That is what I define as sharp. kellyw
 
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WayneD

Guest
as already been said, I think it depends on what the tool is .
personaly I feel that the following is sharp:
straight razors - split hair without any hair bending
hunting axe - must be able to slice fur and muscle with little pressure , but must still be able to chop wood without the edge rolling.
felling axe - must be able to bite deep with just a swing at the tree
pocket knife - must be able to slice through a rolled sheet of A4 (4 layers) with little pressure.
Utility knife - has to be able to slice wood, meat etc without losing its edge
personal protection - must be able to slice through clothing / flesh etc so has to have a fine 'shaving' edge
 

Rock

Well-Known Member
as already been said, I think it depends on what the tool is .
personaly I feel that the following is sharp:
straight razors - split hair without any hair bending
hunting axe - must be able to slice fur and muscle with little pressure , but must still be able to chop wood without the edge rolling.
felling axe - must be able to bite deep with just a swing at the tree
pocket knife - must be able to slice through a rolled sheet of A4 (4 layers) with little pressure.
Utility knife - has to be able to slice wood, meat etc without losing its edge
personal protection - must be able to slice through clothing / flesh etc so has to have a fine 'shaving' edge
Well thought out and said, Wayne.
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
another thought or two on this:

I see two kinds of shaving sharp. I can bring a sharp blade across my arm and cut hair. The hair and skin cells pile up on the blade. That is shaving sharp. It may or may not slice paper with out snagging. Not a thing wrong with this edge.

If I take it a bit farther, I can take the same blade across my arm and see hair literally jump up and scatter when cut. The hairs will not pile up on the blade but they "pop" out of the way. This edge easily cuts paper along the entire length of the blade with out snagging.
 

Sean Cochran

Well-Known Member
I was hoping to get some good answers, you guys have given some good ones. So here is my opinion FWIW.
The ABS has a default standard by which sharpness is measured, shaving. I agree, as I think anyone would, that if a knife will shave it is sharp. Is that the be all end all of sharp. I dont think so. For one Tracy makes a good point, that is you can take what some would call a "dull" knife and it may shave, it may not "pop" the hair but it may shave.
At Blade last year there was an exhibition "how to shave with a machete". It would never occur to me to try. I mean it was neat that a machete would shave, but why?
I guess what Im getting at is "sharp" relative the task at hand? I think it has to be.
Just my $.02

Sean
 

HELLGAP

Dealer - Purveyor
Tracy is totally right , their is whole other lever of sharpness most people never take it to. I dont see the need to go to that extream unless they are straight razors.
 

Cliff Fendley

Well-Known Member
Maybe not necessary on a regular knife, shaving sharp is good enough but when a hunting knife is that "hair popping" sharp it just makes the job that much easier.
 
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