Someone knows how to sharpen a knife

[Steven Mikes]

Someday I'll do this to my kitchen knife..


https://www.reddit.com/r/oddlysatisfying/comments/gp8z5e/today_i_sharpened_my_favorite_kitchen_knive_and/?utm_medium=android_app&utm_source=share

[Mike Allen1010]

OMG! I give up now – that's a level of sharpness I've never achieved in a lifetime of sharpening!

I want to find that guy to persuade him to teach me to do that. I at sharpening knives – can never get the bevel angle right etc. Seems like some kind of reversible, motorized sharpening wheel would be helpful. Just a guess I got no idea how he gets it that sharp.

[David Eisenhauer]

Impressive. Thanks for sharing Steven.

[bill epstein]

Amazing! Further down the page this caught my eye https://www.reddit.com/r/oddlysatisfying/comments/gptvlx/thats_how_they_make_a_tunnel/?utm_source=share&utm_medium=web2x

[Winston Chang]

OMG! I give up now – that's a level of sharpness I've never achieved in a lifetime of sharpening!

I want to find that guy to persuade him to teach me to do that. I at sharpening knives – can never get the bevel angle right etc. Seems like some kind of reversible, motorized sharpening wheel would be helpful. Just a guess I got no idea how he gets it that sharp.

I recently learned how to sharpen kitchen knives, and I think it's actually easier than freehand sharpening woodworking tools.

Maintaining an exact angle isn't as important as it is for chisels and plane blades. I'm not an expert on knife sharpening, but I have some theories about why this is.

- With knives, a rounded bevel isn't really a problem like it is for chisels and plane blades. A rounded bevel on a chisel or plane blade will tend to get more rounded over time (unless you make specific effort to correct it). With knives, the blade is much thinner and the bevel is much smaller, and there's much less material to remove, so a slightly rounded bevel doesn't really cause problems -- you can easily reset the bevel next time you sharpen. Because you can easily reset the bevel, this means you can add a microbevel on a finishing stone without worrying about causing problems later on. The exact angle of the microbevel doesn't matter; it just needs to be a little higher than the rest of the bevel.

- Since you sharpen both sides of a knife blade, this makes it easier to get a sharp apex. With chisels and plane blades, you usually work the bevel side a lot, and then try to cleanly remove the burr from the back, and in my opinion, that's a more difficult operation to do well.

- As mentioned earlier, knives a much thinner than chisels and plane blades, so there is much less material to remove, so sharpening them is much faster.

- Finally, knives don't need to be as sharp as woodworking tools to work well. A little toothiness is actually considered helpful in kitchen knives, so after a certain point, a cleaner, more polished edge is actually detrimental for most real-world cutting tasks.

To do tricks like the sideways grape-slicing in the video, it helps to have a very shallow bevel angle. Here's a video I made doing the same trick with a knife that's sharpened to 12 degrees on each side. Before doing this, I refreshed the edge on a 4000 grit stone for about a minute. That's a relatively low finishing grit by woodworking standards, but a little toothiness helps for slicing cuts like this. Here's a link -- hopefully it works!

https://imgur.com/EY2VKiI


For learning how to have a somewhat-consistent angle, I found it really helpful to use these plastic angle guides. They're just wedges at specific angles. You put one on top of your stone, then bring your knife to the wedge to find the angle, then you move the knife along the stone, trying to maintain angle. You can return the knife to the wedge to make sure that you're still at or close to the correct angle.

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One more thing: I'd venture that your woodworking tools are sharper than my knife and the knife from the original video. But they also aren't long enough to make big slicing cuts, and they're also much thicker than the knives, so if you tried to slice a grape like that with, say, a plane blade, there would be much more resistance from wedging action than there is at the cutting edge.

[Mike Allen1010]

Winston, thanks a lot for your insight and suggestions – super helpful!

I was struck by the width of the blade of the knives used in both yours and the original demonstration. Seems like wider blades like that would make it easier to get such a shallow 12° bevel angle.

Looking at most of my woodworking knives seems like blades are a lot thicker and bevel angles is steeper than 12°. I want to learn how to do this great kitchen trick!

Best, Mike

[Winston Chang]

I was struck by the width of the blade of the knives used in both yours and the original demonstration. Seems like wider blades like that would make it easier to get such a shallow 12° bevel angle.


The knife I was using was a normal size chef knife. The part that's beveled 12 degrees (on each side) is tiny, probably only about 1mm wide. The rest of the knife has a "bevel", though the angle is very shallow, maybe 1-2 degrees on each side. This is all just to say that you can probably do this on a knife you already own. :)

Incidentally, I was inspired to try this out with a plane blade that's sharpened to about 32 degrees. The angle is larger than the knife's 24 degrees, but the edge is much more refined, since it's finished on a Shapton 12000 grit stone. I ran out of grapes, so I used a cherry instead. The blade was able to start the cut very easily, but didn't make it very far before it started moving the cherry. I think it's because of the wedging action -- the plane blade is thicker, and the cherry is more substantive than a grape, leading to more resistance. Anyway, I think if you try doing this with blades you already have, you might be surprised at the result!