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Comment by rlonstein | Hacker News Reader

Nice. I learned this "at the knee" from my grandfather and father. A few things in no particular order... This skill takes practice, the sharpening systems only help to get the angle consistent; you'll be happier if you learn to do it without one, practice on knives and especially scissors you don't care too much about first, you'll need a few stones and probably end up with several before you find the ones that work best for you and your edges, razor-sharp is over-rated except for skinning, wood planes and chisels and it's harder to maintain; working-sharp is plenty.

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Re your last point: There is some well researched material, along with scanning electron microscope images of edges, that says this is incorrect. When sharpening to say “working sharp” you leave a burr on the edge that can quickly be folded over, and reduce longevity of the sharpness of the edge. The most durable edges have been deburred to the true edge apex, and this often will give you an edge that would rate “razor sharp” or ~50 BESS on a sharpness tester. This has been proven out in a real life commercial setting, slaughterhouses. The edges that Dr. Kraichuk sharpened would stay sharp for 7 full carcasses, rather than 4-5 done with previous methods that can leave a burr on the blade.

For more information about this, including the proof with SEM photos and extensive testing via scientific method, check out the work of Dr. Vadim Kraichuk

https://www.amazon.com/Knife-Deburring-Science-behind-lastin...

There is a lot of discussion about this in the Tormek forums, where Dr. Kraichuk was a frequent contributor. I can attest to how well this works, every knife and woodworking tool in my house is hair splitting sharp, and they stay that way with little effort.

I don't disagree at all but this might be a problem with folk knowledge and terminology. I was taught to remove the burr or wire, you could feel it, and took it off with a steel or ceramic stick. My grandfather was a machinist and woodworker and I doubt he knew what the edge looked like. "razor" meant a pass with very high count fine (3k, 6k+) stones and maybe paste (I have green paste... I think it's Chromium Oxide ~45k) and leather strop. I'll do that for my straight razor, I don't for the kitchen knives.

I'm not going to break out references to everything in the Knife deburring book, but I'd advocate that anyone who wants proof of what I'm basically parroting back (with photos and sharpness tests, wear tests, and real world tests to back that up) read the book.

Once you've ground an edge, there may be a burr or wire that you can feel. Secondary honing brings that edge to something so fine, you can't see it or feel it, but it's not the edge apex. There is either a wire edge so small you can't see it, a feather edge, or a foil edge. These edges after honing may even pass sharpness tests, but will almost immediately roll and lose sharpness. This is exacerbated by the modern "super" steels and stainless steels that are used in knives today, and that is a whole other avenue of discussion.

For example, take a pretty bog standard Global kitchen knife. This is a high vanadium content stainless steel, so it should be ground with a diamond or CBN wheel. Sharpening with conventional abrasives will actually erode the substrate steel around the vanadium carbides in the blade, giving the edge a toothed appearance that eventually results in carbide breakout during use. Because these knives are an "in-between" burr forming steel (which means they don't necessarily form a positive burr or negative burr) and because the vanadium carbides need to be honed away with diamonds, the recommended method for honing this knife would be to sharpen 12 deg per side edge angle, progressing up to 1000 grit CBN or diamond wheel while grinding into the edge, then de-burr the edge with a slotted paper wheel at 5 micron diamond paste, then with felt wheel running away from the edge, impregnated with diamond spray at 1 micron, and +0.8 degrees edge angle. This will remove the wire edge and deburr the edge down to the root of the edge apex. Then hone with slotted paper wheel with Chromium Oxide (which is about grit level 60,000 or 0.5 micron) on a paper wheel for the last pass. This should read about 40 BESS on a tester, and a SEM photo will show no foil or feather edge. That is about 10-15 BESS sharper than a safety razor, but that is what is required to get rid of the different type of burrs that will cause the knife to dull quickly. These degrees are very precise, free-hand sharpening will not end up with the desired effect.

Anyway, not far off what your grandfather recommended, but somewhat different. According to Dr. Kraichuk's testing, leaving the knife more dull than 50-90 BESS almost always has an undesirable edge burr, be it foil, feather, or wire. This burr will roll over almost immediately under use, bringing the knife to a "working sharp" level of 300 BESS, which is pretty bad.

I can't really summarize this book in a HN comment, but if you're at all interested in this research, check out that book. You can get it on a PDF from the author's website, http://knifegrinders.com.au but the author died suddenly so don't look for any support.

> razor-sharp is over-rated except for skinning, wood planes and chisels

Razor-sharp is quite useful for razors. It's much safer to shave with a razor-sharp razor than a dull one.

Well, yes, and my straight razor is that sharp. Kitchen knives no and certainly not hatchets or axes.

Razor-sharp knives are safer to use than dull ones. Earlier today I was invited to a dinner by a family member, and she cut her finger, because, in her own words, she had to apply some force to cut an onion and she lost control of the knife (seriously, the f*king onion. It's ridiculous and I blame her husband for being lousy at sharpening). Cutting with razor-sharp knives requires almost zero force applied, which means you can focus on precision of movement, not strength.

Occasionally a newly sharpened knife when you've only seen dull ones can be dangerous too. If you have only ever encountered dull knives, you get used to the "press and wait til it breaks through and slams uncontrollably" to the point where you can mostly* get by, but you're not as used to safe handling when just getting ready to cut.

Sharp is still safer in general!

Or you can buy a jig like Spyderco Sharpmaker and have a razor-sharp edge in 5 minutes.

I find the Sharpmaker great for touching up an edge, but not nearly aggressive enough (without adding an aftermarket set of diamond rods) for repairing or setting a new edge

I used to own one, but I find the rods too short - it's good for small, 12-cm blades, but it's useless for anything bigger.

Right now I switched to proper water stones :)

this is basically the 2023 answer

I don't care if you are a fifteenth generation swordmaker who practiced for sixty years...you cannot hold a blade in your hands steadily, at sub-mm precision, for more than one stroke

changing the angle even slightly is effectively starting over

but if you must go old school - BELGIAN COTICULE...all other sharpening stones are inferior, it is no contest imho

>> you cannot hold a blade in your hands steadily, at sub-mm precision, for more than one stroke

That's what the guiding rails are for... So far whetstones with guiding rails are the best sharpening method I found. As you can see from my other comment in this sub-thread, I find Spyderco lacking.

This is FUD. If you believe this I have some $8000 speaker wire to sell you.

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