So, how do YOU evaluate "sharpness"?

Whichever method one chooses to use is not as important as to use the exact same test medium each and every time. This allows for a more reliable referance point to which comparisons can be made.


--Dave--
 
I agree. Consistency is important. That's why I focus on the fingernail test, because I can check out any knife anytime with it. Cutting paper or plastic or foam isn't always practical. I check by the tip, the middle, and by the ricasso. and then the same on the other side of the blade.

This allows me to check for a wire edge. I run my thumb across the edge, moving away from it, then flip the blade and do the other side. If a wire edge is flopped over, you can feel it on the one side. Then stroke the edge with a piece of ceramic and you'll feel it on the other side. :) Then go ahead and stroke a few times on each side at a more obtuse angle to break it off.
 
I fully duct tape the yellow pages and throw it into the air, if I can cut it into 4 equal pieces before it hits the ground, then my knife is sharp enough. LOL J/K ;) No really I do what most of you do with the finger pad, thumbnail, and paper tricks. PGH~
 
I've been sharpening knives for a loooong time (my grandfather had me sharpen his when I was a lad, before I was even allowed to carry one!), and I tend to rely on feel while sharpening. I check my work by pulling the pad of my finger or thumb across the edge (perpendicular to the edge, of course!) as I go, checking the entire length of the edge, and from both sides to check for a wire edge. Once it feels consistently sharp from choil to tip, I give it a stropping, and then do a final check: a long drawing slice through paper, again from choil to tip. If it cuts smoothly along the full length, it's good-to-go.
 
I see how easily the knife will shave hair and also how easily it will split notebook paper. If blade will cut the lines of fairly thin notebook paper with ease then you have a rpetty sharp blade. I also use the paper slicing method.
 
ewjax said:
I'm curious - how do folks evaluate just how sharp their blades are?

It seems very subjective to me. For me, I typically tap the edge of the blade on my thumbnail, and gauge the sharpness by how well it "sticks". Or sometimes I slice paper, but again, that is fairly subjective - the length/ease of the cut is very dependent on how hard I swing, the angle at which I strike the edge, the stiffness/flimsiness of the paper, etc. Doing it with a relatively stout piece of paper, as opposed to something flimsy like newspaper, gives totally different results. So it is hard to gauge whether one edge is sharper than another.

I hear people talk about shaving the hair on their forearms, but to me that seems even less reliable or indicative than the thumbnail or paper tricks.

Anyone have any more reliable method than these mentioned?
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When I get a BURR when sharpening I know the blade is about as sharp as I'll ever get it so I'm not big on testing since I can't get a finer edge without reprofiling probably.

If you can hold on the edge of a plastic ballpoint at an acute angle it is pretty sharp.
 
I simply test how easily it can shave, if I want to go all out I look at the blade with a magnifying glass under light to make sure the edge is perfect.
 
Cliff Stamp said:
This fairly high, how do you do the cuts?

-Cliff
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I do a fairly slow draw cut with the blade pointed up about 45 degrees. I was inspired to try it by Wade F when he posted pictures of his single-ply TP cuts in the general forum a year or so ago. I don't know how he actually cuts when he does his test. My knives will not push cut TP without tearing it.
 
I know mine are fine when I can cut hairs off the arm with the blade having no contact with the skin.

Ive been trying to pull this off as well:

Rules:
Single ply paper. No doubling up on the roll. No overlapping to make the tube wall thicker than one sheet.
Taped on top and bottom. 1.5"-3" tube.

Cut the tube freestanding, leaving the bottom half of the tube standing.

This is as close as i've got:
http://www.schottworld.com/camp/paper2.MPG
http://www.schottworld.com/camp/paper3.MPG
 
I know my blade is sharp when it can scare the hair off my arms while still in my pocket.:D

It was mentioned somewhere in this thread before, about using a loupe or some sort of magnification, I generally use anywhere from 6X to 10X magnification to view the edge, lighted magnification if you you have it, usually you can pick these up on the internet for between $20 and $100(remeber you get what you pay for here, so buy the best lens you can afford first and a lighted magnifier should be a second consideration)

With the new crop of LED lighted magnifiers they are much smaller and brighter, add to that the longer battery life, better natural color rendition and a more consistant light and you have one of the tools needed to determine if your knife is sharp enough.

Sharpness is really realtive to the material being cut and the object doing the cutting, stone axes were sharp enough to drop a tree way, way, back when, were they sharp enough?

I know I'm rambling(only got about an hour and a half of sleep last night) but before you can really evaluate sharpness you need to do a few things:

1) You need to know what sharp is, you need a reference, find a knife you think is sharp and does what you think a sharp knife should do and examine it under lighted magnification(if you don't have a lighted viewer go outside on a bright day), examine the edge closely and notice how the bevels are flat and even on both sides, commit the finish to memory so when you see your sharpened knife magnified you'll know how it compares.

This is a basic visual inspection and if there are any problems that are not obvious you'll see it under a magnifier.

2) This is more an interpretation of physical charicteristics, like how easily it seperates various materials, ranging from toilet paper and packing peanuts to the actual material it will be used on.This portion of the process is purely subjective, if your happy with the way it cuts no matter what anyone says, it's sharp enough for you.

3) This has more to do with durability rather than actual sharpness, how long will the knife perform to your satisfaction.

I used to put a 25 degree inclusive bevel on my work knives, other people aren't happy unless they can filet a hair, and still others are happy with a Ginsu knife.

I guess what I'm tryin' to say is learn what sharp is and how to recognize it before evaluating it.
 
IUKE12 said:
Feb 2006 issue of Blade magazine, good article on sharpening."How many passes does it take?" A.G. Russell tests sharpness by slicing foam packing peanuts. On the same line as the foam ear plugs slice test.
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The important thing is to slice a VERY thin slice from the peanut. Use the entire edge and from both right and left hand. A. G.
 
generally if I can shave the hair off my arm and push cut through newspaper, then I figure it is sharp enough.
 
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