A good indication of sharpness?

Bernoulli said:
Slice through thin air quickly. If your knife is sharp, you should hear a snap as the air molecules come back together.
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I read a story a long time ago about an atom splitting knife. The fellow (might have been a Marine and his Kabar) could sharpen so well that when he shot a thin stream of water at the edge you coul hear a faint hiss and nothing going past the blade as the hydrogen and oxygen lost their bond.
 
So some guy shot a 1 molecule diameter stream of water at a Kabar and it split the water molecule in half leaving HO.5 Since O lies in the middle it would be cut in half.

Also I tried slicing air, the force of the molecules rebinding shattered the top of my knife, you owe me a new one.
 
I typically use the shaving test, and occasionally cut up some printer paper as it looks more impressive.

The big question with the shaving test is whether to use your arm or your leg. I usually use my arm, which means my left arm is almost always bare in patches. I have thought of using my leg, but the darker hair would make the bald spots more obvious, even though fewer people would see them.

On the other hand, we do have a cat in the house...
 
Yep, I just run the edge through the arm hair above the skin. If the edge is sharp it will snag and bite into the hair, cutting at least some. When it does that well, it will usually cut a hanging strand of hair by gently rubbing the edge along the strand. It will catch and either cut through or split the hair lengthwise.
 
IMHO, if you're going to use armhair, the blade should effortlessly, "Clean" the area, getting EVERY hair with one pass.

At that point, it will pushcut newsprint.

Ben
 
I just shaved my arms in hope my hair will grow back even, and I will find a new way to determine sharpness :eek:
 
You do begin to wonder if you're getting fanatical when your arm and leg hair disappears from the shaving tests.
 
In my long life, it has been my experience that any worthwhile endeavor requires sacrifice of one kind or another.:eek:

If you wish to play the violin well, then you must sacrifice many hours of your precious time in practicing scales.

If you wish to carry sharp knives, then you must be willing to accept the sacrifice of arm and leg hair!:D
 
Ben Dover said:
In my long life, it has been my experience that any worthwhile endeavor requires sacrifice of one kind or another.:eek:

If you wish to play the violin well, then you must sacrifice many hours of your precious time in practicing scales.

If you wish to carry sharp knives, then you must be willing to accept the sacrifice of arm and leg hair!:D
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Hahaha that is so true.
 
I usually see if my knives are sharp by either the vertical thumbnail test or the "hair on the back of my head"-test. Slicing paper is just to impress others.
 
I have measurement method - cutting thread on the weight. It require 21 cuts to have enough statistic to show sharpness. Based on this I developed scale of sharpness which maps pretty well on thread test but do not require too much effort.

1. Cutting newspaper.
2. Shaving
3. Cutting free hanging hair with fast moution
4. Slicing paper from surface
5. Slicing skin from fingertips without blood
6. Cutting free hanging hair with very slow motion.
7. Slicing free hanging hair
8. Whittling free hanging hair.

Slicing, whittling hair is what I currently use to test final sharpness.

Just finish my Microtech CPM S90V - with all this vanadium carbides etc it whittle hair at the end without any difference from INFI or 154CM.

Thanks, Vassili.
 
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