Do you test sharpness while still in the vise?
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Since it’s a hassle to take the knife out of the vise after each grit to check for sharpness then realign and re-clamp, I was wondering if you guys have found a good way to test for sharpness while the knife is still in the vise?
I tried cutting some carpet foam (1/2″ thick and fairly dense open-cell foam) into ~1.5″ wide strips, and pulling that across the blade while still clamped, but I’m not sure if that’s a good test. For a knife in relatively good condition where I went 400-600-800-1000, I found it cut the foam easily and cleanly after 400 and 600, but took a bit more effort after 800 and 1000. Yet when I took the knife out after 1000 it sliced paper pretty easily.
Might this be a case where the foam just happens to cut best with a toothy 400-600 grit edge, so it’s just not a good material to use after 800 and 1000 grit? The reason I’d like to use the foam is just that I have a ton of spare carpet foam so it’s expendable.
Lots of people prefer a toothy edge as a working edge, some people like that at 600, others at 1000 depending on steel and cutting application. Those little teeth work well for some things as perhaps your foam is showing. In the folder world a common edge is a toothy mirror polish, which is a lite stropping to bring out some shine on the edge after progressing to 1000. So leaving the teeth in place.
I don’t sharpness test in the vice, I want to get into a microscope for that. But if applicable, it would be a great time to try your HHT.
I have found that my USB at 250x is very inconclusive as to how sharp the edge is and even if a good burr is raised. It is very good at scratch patterns.
For the burr, nothing beats feeling it with fingers along the entire edge (vertical up strokes of course on one side only of course).
For sharpness while mounted, I have tried many methods but my go to is my thumbnail scrape (not cut). The nail will catch easier and easier as the knife gets sharper. This correlates well to my dismounted test of shiney rolled paper squiggly cuts, phone book paper, etc.
Its actually the only use of a phone book these days for me. LOL
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I have found that my USB at 250x is very inconclusive as to how sharp the edge is and even if a good burr is raised. It is very good at scratch patterns.
For the burr, nothing beats feeling it with fingers along the entire edge (vertical up strokes of on one side only of course).
For sharpness while mounted, I have tried many methods but my go to is my thumbnail scrape (not cut). The nail will catch easier and easier as the knife gets sharper. This correlates well to my dismounted test of shiney rolled paper squiggly cuts, phone book paper, etc.
Its actually the only use of a phone book these days for me. LOL
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I use my thumbnail to see if the edge bites in easily and that’s usually enough. It’s probably safer and smarter to just use a plastic pen or marker for the same effect: hold the marker/pen at an angle to the blade, ideally similar to the angle of the stones, and set it on the edge. If the edge bites into the marker/pen and holds it, then you have a sharp edge.
-Clay
I do test the sharpness in the vise after each grit, starting at 200 or 400 and then every progression after. I use a sheet of phone book paper held between my first two fingers and my thumb. Starting at the heel at a 45 deg. angle I push the paper into and along the length of the blade. When the blade starts to get sharp you can tell from sound, feel and visual inspection of the cut in the paper. The sound will get wispy and softer and the feel will become smoother and smoother as the edge gets sharper and sharper. I don’t visually inspect every edge I do, I do visual inspection (loop or microscope) when I get an unexpected result or when I have the time to experiment or test one thing or another.
Testing for a burr gets easier the more you do it, I use two methods. Mostly I use my forefinger nail and push my nail up the blade and feel for a snag on the nail the length of the blade. I’ll use this up to 600 grit. If I have to test for a burr past 600 I’ll use a Q-tip laying it on the side of the blade and drag it up the side and if there is a burr is will snag on the Q-tip quickly, if there is no snag when dragging it past the edge then there is no burr.
I would recommend that you test sharpness as well as looking through a loop or microscope. The visual evidence will sometime contradict the sharpness test but the more experience I’ve gained it’s easier to be able to use a microscope especially and inspect for scratch patterns and edge quality.
For me though if the knife cuts properly and feels good and sharp, that is the test I’m most interested in!
Might this be a case where the foam just happens to cut best with a toothy 400-600 grit edge
You will find that different materials like different edges. Most butchers don’t prefer a toothless edge, a toothy edge in my experience works well for raw meat, tough fruits and vegetables, some fibrous material ect. ect. The trick is getting the right finish for the knifes purpose, geometry, thickness and who is using it. While “sharp is sharp” not everyone likes the same edge. Find what you like first, experiment, don’t always think “in the box”.
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