Sharpness test

R

reaper185

Joined
Jan 23, 2023
Messages
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Quandary, riddle me this? If armhair shavin' and wittlin paper be a good test of pushcut type sharp, like razor sharp.
...then what typ of test would be better for slicey sharp from a toothy edge intended for use with a drawcut type action?
 
Paper towels, the cheap thin kind, are what I use to test how toothy an edge Is. Also, toothy edges arent only pull cut, you can orientate the micro serrations to work in a forward cut as well. It’s entirely dependent on how you sharpen.
 
Push or pull, I personally don't care much...
I never being big on following online tests, not a huge fan of trashing knives videos, or any non-standardized tests.
I still like to look at some because they carry some useful information, I like more information on subjects.
My benchmark for "tests" is BBB on YT and also opinions of the members of this forum, I found ton's of useful info.
My determination of sharpness is loosely say - if my working knife retains good working sharpness after such test,
I'm happy. Unfortunately, there is no general opinion about it because different people do different things with their knives and prefer different steels,
therefore - different bevel angles and finishes and the matter gets really wide open for preferences.

This is a "test" i did for another knife forum, Endura 4 ZDP, great knife BTW.
 
I cut more baling twine than anything else. So I've been thinking about getting a scale, such as an archery scale, that measures peak force. Hang up the scale, hang a loop of baling twine from the scale, and see how much force is required to cut the loop. Compare pushing, slicing, hacking, stabbing, whatever, in addition to comparing knives. A scale that integrated force instead of just measuring peak force would be better, but I have never seen such a thing.

The next step would be to hang a bale of hay from the scale, zero it out, cut the two strings, ...
 
For toothy bite in a slicing, drawcut fashion, it's simple in terms of the materials used and the method. What you observe while you're doing it is the main thing:

Test the edge in slicing fine paper, like phonebook pages, catalog pages, receipt paper, newsprint, etc.

Make repeated slices through the paper - both slowly and quickly. While doing that, watch for any slips or snags during the cut, or tearing of the paper. That will show you where burrs are, or where the edge needs to be more completely apexed.

When slicing in the paper, also watch for how straight each cut is. If you notice each cut tends to turn or arc in one direction or the other, that's an indication the edge geometry is asymmetric (bevel angle different on each side) or not centered relative to the spine. But if the edge sails through the paper in a path aligned with the blade's spine, then you know your edge is balanced & centered.

If you see erratic behavior from one cut to the next in paper, that could be a sign the edge isn't stable or strong. In other words, the geometry might be too thin to be stable, OR there's still a sharp but flimsy burr along the edge, which moves back & forth with each cut. You might see the edge sail through the paper on one cut, and then snag or tear the paper, or slip, in the next cut. And then on the next cut after that, it might cut cleanly again. That erratic behavior tells you the edge isn't stable enough to hold its shape. A quick fix for that: a tiny, barely-there microbevel applied in just a pass or two per side, with a medium or fine ceramic at the lightest possible touch will strengthen the apex and can also narrow the apex width, which makes cutting aggression even more so.

The above is what I always do, to test the edges I like on all of my knives. If they handle these tests^ well, then I know they'll do everything else I expect of them in normal use. I've never been let down, doing it this way. You can do other things as well for 'bonus' testing, like seeing how easily the edge will bite and slice into the face of the paper, instead of the edge of the paper. And I sometimes test with paper towels as well, to see just how keen & stable a toothy edge actually is. As with the other paper, any snags, slips or tears will be much more obvious in a paper towel, and will point out portions of the edge that could use more work.
 
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I've gotten to the point in my obsession where I won't pocket a knife unless it will whittle free-hanging hair. It's not healthy. 😂
 
Sharp but toothy edge - best draw cut test is on a Cherry Tomato. Blunt wont slice it and too refined ( polished ) will slide off and not bite in.
 
Stockman said:
Sharp but toothy edge - best draw cut test is on a Cherry Tomato. Blunt wont slice it and too refined ( polished ) will slide off and not bite in.
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A highly refined, polished edge should go through tomatoes like a laser IME. Depending on the steel it may not last for very long though.
 
chalby said:
A highly refined, polished edge should go through tomatoes like a laser IME. Depending on the steel it may not last for very long though.
Click to expand...
Give it a try, sharpen a kitchen knife down to about 2000 grit, this is where I like my kitchen knives with a bit of toothiness, and it will slice ripe tomatoes with ease. Then sharpen that same knife up to 8 - 12,000 grit and strop on 0.25 mic paste, this will shave like no tomorrow, slit hairs etc, but will struggle on a tomato.
The skin on the tomato, especially cherry tomatoes are rubbery and smooth and require that bit of toothiness to initially tear the skin to start the cut.
 
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