When is a knife sharp enough, and how to you test?

ziggy925

ziggy925

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Oct 4, 2009
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I'm talking general pocket carry and maybe SD. How do you know when your knife is sharp enough? I generally test by slicing through the edge of a single sheet of paper, but how do most of you test the sharpness of a knife?

I am also aware that "sharp" is often a compromise between razor sharp and how long the edge will last. I guess I'm also asking if a knife can be too sharp.

TIA
 
Depends on what my applications are and what shape the blade is. Usually, I'll get it to push cut newsprint an inch from my hand, but I find that a toothy edge works nicely for general kitchen use. That means my Henckels usually gets a 600 grit treatment.
 
Push cut newspaper, shave without touching the skin and if I have the time, I'll go through a box with 100-300 slices or so to check for edge retention.
 
A general rule-of-thumb for testing "working" knives is to place the edge against your thumbnail at an angle. If it is sharp enough, it will catch against your thumbnail and not slide, but if it isn't sharp-enough, the knife will slip.
 
I usually draw the blade through my hair. If I feel the edge catching, it's sharp enough for most uses. It's similar in results to the arm-hair technique, but you don't end up with hairless arms.

Cleanly slicing toilet paper is always a good test, but it requires a very sharp edge.
 
the two i do are a light scrape against the pads of my fingers. With experience you can judge the sharpness by how good the edge catches the prints of your fingers.* the second test is to contact shave a few hairs. If the hairs pop with no pressure against the skin, your good to go.
 
Sharp enough, for me, is when the blade will shave arm hairs.

Scary sharp is when the blade can whittle or cut free hanging hair.
 
Another vote for shaving arm hair here. I don't need my knives to be any sharper than that.
 
enough to shave hair for the little edc blades, or enough to catch a fingernail for the ones i'm going to be rough with
 
If it push cuts newspaper it's more than sharp enough to make hair pop off your arm. :)
 
Most all of mine will push cut news print. I am mainly a hunter so that is more than sharp enough. I like a bit of a toothy edge for meat cutting and I do a lot of that.
 
YayILikePie said:
Depends on what my applications are and what shape the blade is. Usually, I'll get it to push cut newsprint an inch from my hand, but I find that a toothy edge works nicely for general kitchen use. That means my Henckels usually gets a 600 grit treatment.
Click to expand...

This is the best way of putting it, if you're going to use your knife to hack through brush you don't want a super sharp edge, however I keep a very fine edge on my SAK which need to be able to make clean cuts through things like paper.

P.S. It's sharp enough when you can cut time. :eek:
 
Lots of good info. Thanks. My knife will catch on my thumbnail, and I can "slice" a piece of newspaper. I'm not sure what you mean by push cut. If I push the edge of the knife against a piece of newspaper it just crumples, but if I take a quick slash at it the paper easily slices off cleanly. How's that? I'm achieving this with one of those tri stones -- three stones mounted on a triangular form -- and a diamond steel. The Magic Marker trick I read in another post really helped a lot.

Well, If I stab the paper and gently pull the knife through it the paper also slices cleanly. Can't pop any hairs off my arm, however.
 
a push cut is when the knife cuts the paper instead of crumpling it. There is no drawing/slicing motion.
 
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