How do you like to test for sharpness?

I'll touch the edge with my thumb first. Then shave some hair. That last bit is better in the winter when I'm wearing pants. Summer I'm all patchy. I'll do paper and the finger nail too but hair is where I know I'm good with the sharpness level.
 
sharp_edge said:
In the following order:
- Feeling with finger tips
- Slicing flat piece of phonebook paper, both straight and curly, fast and slow
- Slice single roll of phonebook paper (this is basically what NJBill described above)
- Splitting hair
- Staring at the edge to see if my eyes bleeding (not happened yet)
Click to expand...

Cutting through thin paper SLOWLY definitely a pretty good indicator...
 
I'll use one of my fingers, usually a thumb first. I will frequently try to cut some regular copy type paper. Seldom do the hair thing. If for some reason I cut myself, that's the way the ball bounces because I was careless.

Some people do finger nails.
 
Emre,

Looks like you have some great test methods already developed for yourself. The important thing, from my perspective, is that I try to look for new ways to test (much as you are doing right here). I would say with whatever test being used, attempt to make the test as hard as possible. I find that many times we make any test easier than it could be, based on wanting to succeed. How skilled is the tester performing the test vs. how is the tool performing. Remember years ago when YouTuber test/reviewers illustrated time-and-again how paper cutting could easily be pass/fail simply because the tester did not know/understand the tricks of accomplishing the test the easiest way. Their video cut/sharpness test would fail, "oh, I suck at paper cut testing" then all of a sudden they hit that magical angle of approach and swish ... "there see I told you it was a sharp SOB". The educated eye saw exactly how/why, but the reviewer cared not to actually learn what they were missing. I will comment on this a little below.

sharp_edge said:
In the following order:
- Feeling with finger tips
- Slicing flat piece of phonebook paper, both straight and curly, fast and slow
- Slice single roll of phonebook paper (this is basically what NJBill described above)
- Splitting hair
- Staring at the edge to see if my eyes bleeding (not happened yet)
Click to expand...

^^ Most excellent list there ^^

RE: "How do you like to test for sharpness?
Like the title says, I'm wondering what techniques/methods you guys are using to test sharpness."

Most of my reply is simply an extension of what sharp_edge has posted, with consideration for making any of the tests a bit more difficult or comprehensive.

Depends on the intended application for the knife, what type of edge (geometry & finish) and the test medium. Application; slice polypro rope, push-cut poly-prop rope, cut soft medium (meats, etc), cut hard mediums (plastics, etc.), cut with high-force (chopping, etc.), cut with low-force (feather-sticking, etc.). An edge needs to be sharper to cross-cut any medium with grain (directional composition).

Always includes feeling & testing for bur(s), foil-edges, etc. and typically removing such (unless the application has use for them).

Most times the "test" is/cab-be actually a progression. Example; only using paper could mean a slew of progressive tests with the same piece/type of paper. As an edge progressively becomes more keen, the way the edge is presented to the paper can significantly increase test difficulty or visa-versa. Push cutting progressive circles from an outer edge to the center creating a singular spiral of parallel cut lines is a fun finish that requires a sharp edge and a little bit of skill (usually, there is a little cheating involved before getting to the center - a little draw slicing or push-cutting on an angle). As you get closer to the center, you will necessitate the use of the tip testing the majority of the edge length. Step this up a little and go the other direction (anti-clockwise vs. clockwise in my case). Similar test can be done cutting parallel S- shapes, in both directions. Slicing and/or push-cutting into a rolled (tubular) piece of paper (both with and against grain) is a good way to test the edges ability to penetrate over a wider area of the blade (less direct force applied because the contact area is distributed over a greater area). I believe geometry of the edge will play a more significant roll in this type of test.

Feeling edge with finger(s) tests (pads, nails, etc.) testing that edge is fully apexed with micro-chips and fatigued metal removed.

Inspection (light diffraction, jewelers loupes, etc.) to verify intersection of bevels at apex, and also to verify dimensions. I have a small hand-held Brinell scope (magnifier with embedded scale) that allows me to see & compare small differences in edge dimensions. This makes it easier for me to create even bevels and/or asymmetric bevels (both left to right and also variable from ricasso to tip). These variables can affect cut testing, knowing what's going on helps to judge performance results/goals.

Paper cutting (slicing to push-cutting both with & against the grain) test on various types of paper (how/what the paper is constructed of, it's moisture content and grain direction are more important than the thickness but all play a part in test results). For example: compare typical printer paper to Dex Yellow Pages and paper-towels and/or toilet-paper. The orientation of the apex to the paper has significant effect; much the same way chopping through wood at a slight angle to reduce binding, presenting the apex at 90/90/90 (three dimensional angle of approach) provides highest resistance (test of sharpness & geometry). How it cuts and the result (amount of tearing, etc. - when I say tearing talking about the very ends of the individual paper fibers). Edge will perform based on edge finish & geometry (goal might only be only slicing performance vs push-cutting).

Hair Cutting & Shaving at skin level, progresses to whittling standing hair, progresses to cleaving standing hair, progresses to tree-topping standing hair (multiple complete cleaving of free-standing hair). Thickness and texture of hair makes significant difference in results. My beard vs. arm & head hair respond differently. As keenness of edge progresses I move to thinner hair for freestanding tests.

Each testing level performance along entire edge and from both sides of the edge equally.

Cleanly (horizontal cuts with no tails) cleaving thin hair from both sides of blade along entire edge is typically where my progression stops (many times sooner depending on application). The sound of the pop (noise made by hair cleaving) is a neat affirmation (the first time I "heard" this was one of those ah-ha moments). At this point I may go back to paper of various consistency (soft papers like paper towel and/or toilet paper and test for clean slicing with little pressure and push-cutting), test both with & against the grain. The softer paper fibers are more difficult to cut as they tend to move similar to how thinner hair moves without allowing the edge to bite.
& cut cleanly.

Like with hair, or any test medium, the results are greatly based on the medium.

I have played around with scaled thread cutting (scale attached to a thread to measure force required to cut) and force measurements (cutting on top of a scale, etc.), but found this to be of less effort vs. reward by comparison to the methods above. If I were to run a series of controlled test comparisons (where the edge geometry is exactly the same or where the multitude of variables is controlled ...), I would use scaled measurements and a fixture device to hold/apply the blade edge cut to the medium.

I always have at least a couple grades of hair on my person, so for me getting to shaving, then whittling and possibly cleaving is satisfactory goal. Big issue/variable is consistency of the test medium (hair changes with conditions).
 
We don't have phonebooks anymore, so I use the really swishy thin catalog paper. Has to cut free-hanging smoothly in all four directions before it's done.

I will occasionally sharpen some knives/steels to a hair-splitting edge, but generally don't take the time to do that sort of thing for ordinary EDC or work knives.
 
The knife gotta shave hairs on my arm effortlessly. AND it's gotta do this equally well on left or right. This is coming off the stone. This way I beleive there is no burr. Then i strop it on a piece of just leather additionally cuz i like too. I also like to cut paper towel. Regular paper would be good for seeing how steel does after heavy cutting maybe, but if you been using it for some time you probably a good judge of sharpness with this method aswell.
 
I just stab people. If it goes in and out smoothly, it's good enough for me. (That's what she said)

Sent via carrier pigeon
 
The knife gotta shave hairs on my arm effortlessly. AND it's gotta do this equally well on left or right.
Click to expand...

Important point. (left AND right)

At a minimum I do the nail thing like this. All along the edge and correct where needed. Usually if it will do this it will at least scrape some hair and from there going to easily shaving and hair whittling is just a few careful strokes on a finer stone away.

Yah I know what I said earlier but . . .



Or produce is even better if you have some handy.

 
I do all sorts of thing. The fingernail thing of course. Shaving arm/leg hair. Cutting paper. Cardboard sometimes, but then I have to touch it up again. Cutting through an empty plastic soda bottle. Sometimes I just use a finger or a thumb. Don't worry, I don't cut myself (usually) as I have pretty tough skin on my hands, and I can personally feel how sharp a knife is rather than using some outside medium.
 
I use my thumb at an angle and the more the resistance across my fingerprint the better. Paper is easy for me to cut at any sharpness for the most part 👍
 
Receipt paper
Arm hair
Q Tip push cut
Paracord push cut

G2
 
Armadew said:
I don't know how, but these lines merged in my head (and reversed "tip") and I thought you said Armpit hair. Had to read it again :eek: :D
Click to expand...

LoL you need to seek professional help ;)
G2
 
Paper to check for rough spots on the edge. Then cutting the print off of paper and paper towels or to. Also hair. Checking how the bite increases and very verying angle can show progression of edge. You don't actually have to cut the hair.
 
If I just need a usable edge, I'll use 3 fingers and feel to make sure the edge has little to no burr and not too smooth. If I'm being more picky, I'll slowly slice some really thin tracing paper. When I'm really, really picky and want a "showy" edge, I'll examine with a jeweler loupe. Of course the best test I've found is to swing the knife around in the air and listen for a WOOSH sound so I know it's sharp enough to slice particles in the air. :P
 
Lots of interesting responses. Me, I hand the knife to my girlfriend and stick my arm out. She then deploys the blade and picks out a remaining tuft of arm hair and cuts at it. I watch the hairs to see if they pop off or are just shaved. Stones, green compound strop, then naked horsehide strop.
 
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