Blade Sharpness

G

Gunslinger45

Joined
Aug 11, 2002
Messages
16
What is the accepted standard test for knife sharpness, if there is one? In other words how can I tell if my blade is really as sharp as it can be or if it is just so-so sharp?
 
First off, welcome to the BladeForums, Gunslinger45!

For my test, I usually just run the edges of my blades on my arm hair(very carefully), when it shaves hair with ease...I'm happy. :)
 
Shaving is good until you go on a sharpening binge and up looking like you have mange.

I like to slice paper. A good edge will slice through a hanging sheet of paper cleanly. A real good edge can be used to "chop" peices off of a hanging peice of paper cleanly. Technique is a big part of that one though.

Its also fun to cut free hanging peices of twine (or rope depending on how big the knife is) thats another one that takes a real good edge but also takes just the right technique.

If you do a search on free hanging toilet paper, you should get some laughs along with a lot more ways to test the edge.
 
I hate to sound like I'm straddling a fence, but it depends on the use of the implement. Right now I own an axe and a friend has a barber's razor, and we each have all of the toys--stones, diamonds and the Edgepro. Both the axe and the razor are very sharp, but I'd hate to shave with the axe and chop fire wood with the razor.

I use the 'magic marker' method for setting the waterstone on the Edgepro. I've had some Microtech Tanto SOCOM's with the front tanto edge at 17 degrees. I've seen a Kershaw at 15 degrees.

For a catch-all answer for a general purpose pocket knife, I'd say a slightly toothy edge at 20 to 22 degrees would handle a wide variety of daily chores.
 
I usually try to sharpen my smaller and thinner knives, so that they can easily cut a standard piece of copy paper against the grain. My larger and thicker ground knives will usually just cut the paper with the grain.
 
I test my knives on my thumb-nail...If it'll cleanly and easily shave my thumb-nail, then the blade is sharp...If it won't shave, it's back to the Spyderco Sharpmaker for a few more passes.
 
I'll cut and paste the description I've given before of my method for taking fairly precise measurements of push cutting sharpness:

"As for my sharpness measurement method, I did it as follows: I tied a loop of Johnson & Johnson waxed dental floss to the lid of a sport-style water bottle. I lifted the water bottle (very gently and slowly) by means of the knife to be tested, edge facing up, slipped under the loop of dental floss. I added water to the water bottle in 3-5 gram increments, until the weight of the water bottle was enough pressure for the knife to cut the dental floss. Then I weighed the water bottle full of water."

Let me add to my previous deescription that you must hold the knife with the edge level or very nearly so when doing this. Otherwise, the floss (or whatever thread you use) will start to slide down the edge, and will cut through with much lower weight.

And here are some benchmarks, to put results in context:

cutting at 595 grams=the dullest at which I can scrape shave body hair

cutting at 460 grams=the dullest at which I can easily shave body hair

cutting at 390 grams=brand new factory edge on Cold Steel Gunsite

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The above only gives you a measurement of push-cutting sharpness. Slicing sharpness is an entirely different matter, and I am still working on coming up with a satisfactory measurement method.
 
Originally posted by Ichabod Poser
I hate to sound like I'm straddling a fence, but it depends on the use of the implement. Right now I own an axe and a friend has a barber's razor, and we each have all of the toys--stones, diamonds and the Edgepro. Both the axe and the razor are very sharp, but I'd hate to shave with the axe and chop fire wood with the razor.

I use the 'magic marker' method for setting the waterstone on the Edgepro. I've had some Microtech Tanto SOCOM's with the front tanto edge at 17 degrees. I've seen a Kershaw at 15 degrees.

For a catch-all answer for a general purpose pocket knife, I'd say a slightly toothy edge at 20 to 22 degrees would handle a wide variety of daily chores.
Click to expand...

Are those numbers total edge, or per side?
 
To me, a knife is not sharp enough if you can actually see the edge. Beyond that, I like the thumbnail test. If I run my edge along my thumbnail and it really bites in, then it is sharp enough.
 
EricJ, with the Edgepro, the degrees are measured from the center-line. Their 22 degrees would be a 44 degree combined measurment. I like them a bit sharper, say 18 degrees to 20 degrees.

Those edges are a bit more delicate, but I like things sharp, and I don't mind spending the additional time to keep them that way. Of course, I don't chop with an edge like that.

Everything has an exception. I just got a Strider AR, which is designed for extreme work. The edge is plenty stout, but very sharp; it easily slices a piece of newspaper with very little pressure.

When it comes time to re-sharpen, I will use this factory edge as a guide, and will NOT re-profile it to a finer degree.
 
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