What to use to test sharpness?

MdBlades

MdBlades

Joined
Sep 23, 2003
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Whats a good item to test the sharpness of knives on? (And no, your finger doesnt count, ouch.) I was just wondering what you guys use when you test the sharpness of a knife, because i know that paper will dull a knife, so what should i use? Fruit?
 
I can feel the edge abd get a rough idea what kinda edge i have. Then I cut the hair on my arm , If its really sharp it will shave , but you get a feel of how easily the hair shaves off. If it shaves hair its good to go with me , but I kinda like getting the blade where you just touch a hair and it pops it off almost like magic :)
 
I slice paper, if it's a quality blade paper won't dull it, unless you're cutting up a few reams anyway. My favorite (and showiest) test is to slice a sheet of paper lengthwise in one stroke, so I end up holding half of a sheet while the other half falls to the floor. It makes an even bigger impression if you use 5 or 10 sheets. :cool:
 
Though I'm still relatively inexperienced when it comes to sharpening knives, I can "feel" whether a blade is sharp or not. At first, I did tests (cutting paper, shaving hair, etc) to see if it was sharp. Now I try to feel whether it's sharp or not and once I've made up my mind, I test it to see if I was right. Not sure if that's a good method or not, but it's been working rather well for me.
 
I use legal, yellow ruled paper and arm hair shaving. The long side of the legal paper will bind and resist cutting more than the top and bottom when I slice through very slowly. Hair shaving, as mentioned, has different levels of sharpness: simple shaving, hair-popping etc. My left arm hair is usually in a state of regrowth.

The most difficult test I've heard of (that supposedly tests sharpness) is to take three sheets of toilet paper (that's Un-used for you hard core types). While holding the top sheet try and slice downward through the bottom two sheets without tearing, or tearing out a triangle, of the toilet paper. The ideal result should be just a clean slice. I haven't been able to do it. Close, but I always manage to tear a piece right near the bottom before the blade exits.
 
i usually use paper, because its easily available, and its a good test of what i'll most likely be using the knife for anyway. (opening envelopes, packages). my favorite method is to hold the top left corner and take little slices off the top right corner. if done properly and the knife has been sharpened properly, the paper will come off in longer and longer strips.
 
First I check to see if it can shave hair and then I slice ripe tomato. Sometimes mirror, scary, hair poppin' sharp doesn't cut a tomato very well or for very long. Too easy to roll I guess. Oh yeah... I clean it after the arm hair test. Hairy tomatoes are not too tastey

A toothy edge seems to be the most useful to me for everyday chores.

Bruce
 
I'd say test it on what you want it to cut. If you want it to cut fruit, test it on fruit. If you want it to cut apart card board boxes, test it on card board. Etc.
 
A few things I do to check my edges. One, I look at the edge. If you can see light reflecting off the edge; in fact, if you can see the edge, it's not sharp enough. Two, I slide the edge across my thumbnail. If it grabs, it works for me.

With paper, I like to shave slices off instead of simply cutting corners off. If you can slice layers off, while the paper is laying on a desk, it's plenty sharp.
 
Paper is good start if it slices paper no problem it will shave arm hair and make nice small shavings of you nails.
 
I'm another one who uses my thumb-nail to test sharpness of my knives.
 
I try to test both slicing and push-cutting sharpness. For push-cutting, I shave hair, cut paper, and/or feel with my thumb.

What most people don't do is test slicing. I use the same hard poly rope I have for years. Each knife gets a slice, and because I've done this for a long time and kept the rope consistent, I pretty much know what to expect. The sharpening isn't done until I'm satisfied that the knife can slice the way I want it to.

Joe
 
Besides feel and shaving hair on the arm (if you are not endowed with much hair and you do a lot of sharpening you end up with bald arms to match your bald head) I use leather esp skiving off the edge of 'roo skin, emu skin or buckskin.
 
After checking on my own armhair, I fish one of my girlfriend's long hairs out of her hairbrush or off her pillow. I hold it by the folicle end suspended down. Then I take a swipe at it and see if I can cut off the bottom half. If I can do that 3 or 4 times in a row I'm happy.
 
If you can get a round-bottomed ball-point pen and the instructions of the RazorEdge EdgeTester, you're in business.

Here's my closest approximation:

Hold the pen at a 45 degree angle and hold the blade parallel to the ground with its edge facing downward. Let the weight of the blade 'catch' on the ballpoint pen barrel. If it slides, it needs resharpening; if it catches, it will push cut. Repeat this every .25" or so.
That's step one.

Next up, hold the edge perpendicular to the ballpoint pen barrel and run the edge down the barrel with very little force. If it's smooth, and passed step one, it's sharp. If not, it needs resharpening.
That's step two.

Finally, if the ballpoint pen's end is a smooth, round, run it over the edge from point-to-choil and back. If it's smooth, you're golden; repeat otherwise.
That's step three.

It's cheap, fast, easy, and doesn't have you running around with clean-shaven arms.
 
Seein' as how I have no hair left on my arms I had to improvise.

Styrofoam peanuts are a good medium to test sharpness, a sharp blade will slice right through it,(this doesn't work as well on really thick knives).

If you really want to test sharpness get a pair of those foam earplugs they sell at Home Depot for loud noises, this is one of the most difficult mediums to slice through cleanly. This material tends to compress under the least amount of resistance, but a sharp knife will part it like Moses parting the Red Sea.:eek:
 
If the knife can shave the hair off of my arm, it's sharp enough for me.

Bruce Chang
 
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