# Knife thinning question(s)



## beanbag (Nov 11, 2021)

Hello folks,
I have one of those Tsunehisa / Hokiyama OEM (or whatever it's called) blades that has the hammered finish and Aogami super. Despite putting a new edge on it, it still wedged badly in onions and baby carrots. I guess it must be too "thick behind the edge" or something. Anyway, I did the blade thinning thing where I first mark the edge with a sharpie, and then lay the entire big bevel (3/4" tall) against the stone and grind away, taking the grind close to the apex but not going over.
I don't want to take it to a zero grind plus micro bevel, because that will probably be too weak. I also don't need it to cut with minimal friction, but just be anti-wedge. And also somewhat durable and micro-chip resistant. How big of a (primary) bevel should I leave, what angle, should I try to convex the shoulder of that bevel, what finish should I leave on the big bevel, etc?


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## stringer (Nov 11, 2021)

Just start with easing the shoulders of the wide bevels. Work for twenty minutes and then test in the carrot again. Repeat at necessary. I usually finish wide bevels at about 2k. I micro bevel everything pretty much nowadays. As small and skinny as I can get while not being chippy. But same thing. After you thin, build your micro bevel. Test your knife. Use it. See how the edge lasts and if it chips. Make another adjustment. Test it, etc. 

Don't try and make the knife perfect all at once. Make an adjustment, test it, adjust, test. Get the geometry right then worry about surface finish/aesthetics.


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## rickbern (Nov 11, 2021)

What grit stone are you using? You’d be wasting time with too fine a stone. I start with a 220 shapton for this


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## cotedupy (Nov 11, 2021)

^What they said^ There are a lot of variables in this, and matters of personal preference, but the general points above are important:

Thin with as low a grit a stone as you have that will allow to remove the scratch patterns in a progression after with your other stones. But don't use a 120 if your next stone 800 - bite the bullet and use the 800, it'll take the same amount of time in total, but you'll find it less frustrating because it's more precise (at least I do). Ideally though start low as RB said and progress a bit.

Also as Stringer said - go in stages and worry about the finish after. Easing the shoulders is the better way to do it, but if you feel you're still not getting it right, you can always sacrifice a small amount of material, take it to a zero bevel, and rebuild the edge. That's quite easy to do.

Lastly - before you have a go at it in earnest think about how you want it in the end. Paying particular attention to how uniform you want the grind thickness along the length of the edge, and how that works into the distal taper of the spine. As I say there are a lot of variables, and fun potential to make the knife completely suited and ideal for you. And if you work little bits at a time, and check it a lot, there's not a hug amount of things you can balls up. So go wild!


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## ian (Nov 11, 2021)

Hmm, if it’s wedging in _baby_ carrots it might not be the shoulder of the wide bevel that’s the problem. Might just be fat behind the edge. Idk tho. Also, rouding the shoulder will change the aesthetics and make it harder to polish, if that’s something you care about.

Post some pics? Choil shot, shot of the primary bevel?


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## beanbag (Nov 15, 2021)

This is what I mean:
First I mark the edge with a sharpie.
Then I place the "big bevel" right against the stone and grind away.
The black sharpie line gets thinner and thinner.
I intend to stop before it disappears because that would take it to a zero grind and start to affect the profile.
Plus, I already put on a good edge in the first place and don't want to mess it up.

What I found was that stones of 220 grit, or even "muddy" 300 grits don't work well because:
a) little bits of grit come off and make scratches into the black line. I don't want one of these grit pieces to hit the edge.
b) these stones tend to dish, plus the mud pile-up, causes a convex grind in the big bevel. Then when I move up to the next stone, it takes a really really long time to get all the scratches out. Thus while I might start with a 220 stone, I switch over to a Shapton 320 glass once I see scratches in the black sharpie line get close to the edge. The SG 320 is good about not throwing out grit and dishing, but it does tend to glaze over quickly. (Any suggestions to make it last longer before needing a refresh?)

So anyway, the "shoulder" I am talking about is the top of the black line, not the "shinogi" line. At the moment, both black lines are about 0.6mm thick, and I can almost cut thru a baby carrot without it cracking. I can either continuing grinding away to make the black line thinner, or try to convex the shoulder at the top of the black line. (Already tried a little bit of the latter and it didn't seem to help wedging)


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## stringer (Nov 15, 2021)

beanbag said:


> This is what I mean:
> First I mark the edge with a sharpie.
> Then I place the "big bevel" right against the stone and grind away.
> The black sharpie line gets thinner and thinner.
> ...



Keep doing what you're doing in terms of lying the big bevel down on the stone. Just alter where you are putting your finger pressure. To get rid of the shoulder on that old micro bevel you will have to put pressure down close to that black line. You can do it with a higher grit stone to reduce the impact of slurry dulling and minimize the amount of convexity you add. But it will take more time which will increase the chance of a mistake. It won't necessarily help with wedging but it should help reduce the amount of initial downward pressure you need to get into your product which can make cutting more pleasurable. Also, in general, I feel that people get too caught up on "wedging". It's much more important to me that a knife thinly slice carrots efficiently than the knife cuts carrots into chunks silently.


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## stringer (Nov 15, 2021)

stringer said:


> Keep doing what you're doing in terms of lying the big bevel down on the stone. Just alter where you are putting your finger pressure. To get rid of the shoulder on that old micro bevel you will have to put pressure down close to that black line. You can do it with a higher grit stone to reduce the impact of slurry dulling and minimize the amount of convexity you add. But it will take more time which will increase the chance of a mistake. It won't necessarily help with wedging but it should help reduce the amount of initial downward pressure you need to get into your product which can make cutting more pleasurable. Also, in general, I feel that people get too caught up on "wedging". It's much more important to me that a knife thinly slice carrots efficiently than the knife cuts carrots into chunks silently.


And there's not really much of a way to thin without touching up the microbevel a little after you are done. At least not that I have found.


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## HumbleHomeCook (Nov 15, 2021)

stringer said:


> And there's not really much of a way to thin without touching up the microbevel a little after you are done. At least not that I have found.



This. You're going to need to _at least _refine that edge when you're done.


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## ModRQC (Nov 15, 2021)

I agree with the latter part... well I agree to everything said, but I was about to call the shot until seeing later posts. Even if incremental, thinning the wide bevel while trying not to touch the edge makes the edge geometry more and more obtuse in relation with the overall geometry. I sometimes still see a glint of the old microbevel, especially when convexed, but most of it and mainly its own "shoulder" have been thinned down. I never save the edge, but go at resharpening it straightaway. For a matter of fact, I tend to lightly dull the apex before getting to work anyhow - sort of normalizing a plateau there, and sort of forcing next sharpening to really expose fresh steel. I don't trust to keep an apex that's seen thinning work.


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## stringer (Nov 15, 2021)

beanbag said:


> The SG 320 is good about not throwing out grit and dishing, but it does tend to glaze over quickly. (Any suggestions to make it last longer before needing a refresh?)



Several options:
Atoma diamond plate
Coarse SiC on granite or plate glass
Rub it with another coarse stone
Use a synthetic nagura to "clean" it
Flush it with more water
You can try scrubbing it intermittently with a scour pad or kitchen rag
Sandpaper


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## beanbag (Nov 15, 2021)

stringer said:


> Several options:
> Atoma diamond plate
> Coarse SiC on granite or plate glass
> Rub it with another coarse stone
> ...


Thanks for the suggestions.
But what I meant was, was there something about my sharpening technique that causes it to glaze over prematurely? e.g. using too much pressures, too much or not enough rinsing with water, etc.


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## beanbag (Nov 15, 2021)

stringer said:


> It won't necessarily help with wedging but it should help reduce the amount of initial downward pressure you need to get into your product which can make cutting more pleasurable. Also, in general, I feel that people get too caught up on "wedging". It's much more important to me that a knife thinly slice carrots efficiently than the knife cuts carrots into chunks silently.


I'm not worried about the low pressure to start a cut. What happens is the knife goes in easily but then suddenly stops. Then the carrot will crack and the blade will slam into the cutting board. Before I started this thinning process, it would get stuck with about 1/4" left, then crack and slam. At least now it cracks somewhere near the last 1/8" and there is only a gentle slam. Compared to the Takamura which just glides all the way through with no abrupt increase in pressure.


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## ModRQC (Nov 15, 2021)

Have a look at the choils. Takamura are lasers in the purest sense, and half of the times an almost desesperately V-grind geometry. These usually can cut carrots quite well if sticking is not a problem for the user, but sticky they are. The best of Takamura’s grinds will cut carrots and give you additional food release overall. Baby carrots… if it wedges it’s because you thin the knife without thinning the edge. The microbevel and relative thinness behind are just about the only factors there. The situation you speak of doesn’t make sense to me if you’re not reporting problems also with a rather wide range of produces where we could deduce what might be going on.


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## stringer (Nov 15, 2021)

beanbag said:


> Thanks for the suggestions.
> But what I meant was, was there something about my sharpening technique that causes it to glaze over prematurely? e.g. using too much pressures, too much or not enough rinsing with water, etc.



No I doubt it is you. Synthetic stones have a tendency to glaze/load/burnish and must be periodically refreshed to expose good cutting material. I listed several different methods because depending on your setup and equipment one or another might be easier. And different stones respond different to different methods.


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## ModRQC (Nov 15, 2021)

Don’t forget that the core of these carrots is where most resistance is met. So if the edge is really good, the knife rather thin, but still the edge obtuse, you’ll get an easy enough cutting into but then it might stop dead/crack these carrots.


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## beanbag (Nov 15, 2021)

ModRQC said:


> Even if incremental, thinning the wide bevel while trying not to touch the edge makes the edge geometry more and more obtuse in relation with the overall geometry.





ModRQC said:


> Baby carrots… if it wedges it’s because you thin the knife without thinning the edge. The microbevel and relative thinness behind are just about the only factors there.



I guess I don't understand this point you're making. The actual edge was sharpened at approx 10-11 degrees. That's the black bevel marked with the sharpie. The wide bevel is.. I dunno, something like 1.x degrees. When I thin that down, it's angle doesn't change significantly. The black sharpie line gets thinner, the shinogi line moves up a tiny bit.


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## ModRQC (Nov 15, 2021)

And the edge gets thicker RELATIVELY with the geometry because you try to save it. Which in turns might amount to little less than wedging in small carrots if the BTE is thin enough. Sure, a quite less acute cutting sensation too but how can I know that you know when talking baby carrots?


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## ian (Nov 15, 2021)

I’m not sure it works like that. I mean, sure, thin edge plus thin wide bevel = less wedging, but if you keep the primary bevel angle constant and thin the wide bevel, it’s only going to help. It’s not even like the shoulder of the primary bevel is becoming more of a sharp transition when you do this. The angles of the wide and primary bevels aren’t changing. What’s changing is that the transition happens closer to the edge, and there’s more and more wide bevel and less and less primary bevel.


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## ModRQC (Nov 15, 2021)

ian said:


> I’m not sure it works like that. I mean, sure, thin edge plus thin wide bevel = less wedging, but if you keep the primary bevel angle constant and thin the wide bevel, it’s only going to help. It’s not even like the shoulder of the primary bevel is becoming more of a sharp transition when you do this. The angles of the wide and primary bevels aren’t changing. What’s changing is that the transition happens closer to the edge, and there’s more and more wide bevel and less and less primary bevel.


 
What happens is the v of the edge getting wider and wider proportionally with the relative V of the grind. Want or want not it will result with more and more wedging on small/hard foods while much less of note with say onions if the edge and overall geometry are still thin! You look at this like you would thin, but he says he leaves the sharpie mark mostly intact at the edge. From your own first comment in this thread how can you fail to see this as related with problems cutting baby carrots?


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## beanbag (Nov 15, 2021)

"The black sharpie line gets thinner and thinner"
Post #6


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## ModRQC (Nov 15, 2021)

beanbag said:


> This is what I mean:
> First I mark the edge with a sharpie.
> Then I place the "big bevel" right against the stone and grind away.
> The black sharpie line gets thinner and thinner.
> ...




Plus all you said about not wanting stones that scratches the sharpie line, AND that sharpie line being as wide as we see it in the pic. You’ve worked well in terms of precision, but your knife is thick at the very edge and none too thin above. Honest choil shots might help or not but your focus on baby carrots and not wanting to mess up a previous sharpening says it all.

Edit: especially against a Tak of which we’ve heard none unlogical ways of thinning applied until now.


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## ian (Nov 15, 2021)

ModRQC said:


> What happens is the v of the edge getting wider and wider proportionally with the relative V of the grind.



This doesn’t make sense to me. The knife’s getting thinner. This is only going to help with wedging. Instead of the food having to get pushed apart to make way for a 1mm wide, 10 degree primary bevel, it has to get pushed apart to make way for a .5mm wide, 10 degree primary bevel, which is easier.


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## M1k3 (Nov 15, 2021)

Initiates cut fine > increased resistance > cuts like a champ again? If I'm understanding correctly, sounds like you need a bit more convexing of the bevels.


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## beanbag (Nov 16, 2021)

M1k3 said:


> Initiates cut fine > increased resistance > cuts like a champ again? If I'm understanding correctly, sounds like you need a bit more convexing of the bevels.


No, on the third step, the carrot cracks, so the knife falls thru anyway


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## stringer (Nov 16, 2021)

beanbag said:


> No, on the third step, the carrot cracks, so the knife falls thru anyway



Sounds like a cutting technique issue to me . Use more force. Move faster. Use more lateral movement. And remember what I said above:

"People get too caught up on "wedging". It's much more important to me that a knife thinly slice carrots efficiently than the knife cuts carrots into chunks silently."


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## Jovidah (Nov 16, 2021)

Maybe I'm dumb, but isn't there a huge overlap between 'silent' and 'not wedging' though? Whenever a knife wedges the product goes crack. If it goes through smooth, no crack.


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## stringer (Nov 16, 2021)

Jovidah said:


> Maybe I'm dumb, but isn't there a huge overlap between 'silent' and 'not wedging' though? Whenever a knife wedges the product goes crack. If it goes through smooth, no crack.



Knife technique can play a huge role here. I'll post a vid later


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## beanbag (Nov 16, 2021)

I appreciate the effort, but there's no need to make a vid at this time. I am purposely cutting the same way, but comparing different knives, and this same knife at different levels of thinning.


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## dAtron (Nov 16, 2021)

May we see a choil shot?


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## beanbag (Nov 16, 2021)

dAtron said:


> May we see a choil shot?


No,
It's a stamped blade, so at the heel, the metal is a little different shape, and that affects how the grind looks.
I realized something today, which was to determine how thick is a knife "behind the edge", you should just look at the size of the edge bevel. Smaller = thinner


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## dAtron (Nov 16, 2021)

Ok fair enough. Yeah smaller edge bevel generally means thinner blade. From the other picture you posted,. For how thin I like my knives i would thin some more and wouldn't worry about ruining the edge bevel. If you zero it out you can still reapply it in minutes. You can also introduce some convexity to strengthen the overall edge too.


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## PtownPhil (Nov 16, 2021)

Lunch from the market.


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## ian (Nov 16, 2021)

PtownPhil said:


> Lunch from the market.
> View attachment 152304
> View attachment 152305



This isn’t gonna make anyone thinner.


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## ian (Nov 16, 2021)

beanbag said:


> I realized something today, which was to determine how thick is a knife "behind the edge", you should just look at the size of the edge bevel. Smaller = thinner



I mean, it’s literally true that if your edge bevel is 12 degrees, then the width of the bevel tells you exactly how thick the knife is at the shoulder of the bevel. However, one should keep in mind that “thin behind the edge” to most people doesn’t just mean “how thick would a micrometer measure the knife as being exactly on the shoulder of the edge bevel.” Rather, it usually refers to the overall geometry within a few mm or so of the edge. Imagine taking a chonky wedge-like knife like the Munetoshi butcher, which has like a 10 degree angle on the _wide bevel, _thinning it so the edge bevel disappears, and then adding a tiny 12 degree microbevel with a few strokes. Then it’ll have a really small edge bevel, but noone would call it thin behind the edge.


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## PtownPhil (Nov 16, 2021)

ian said:


> This isn’t gonna make anyone thinner.


Woops.


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## beanbag (Nov 17, 2021)

dAtron said:


> For how thin I like my knives i would thin some more and wouldn't worry about ruining the edge bevel. If you zero it out you can still reapply it in minutes. You can also introduce some convexity to strengthen the overall edge too.



I agree with your sentiments and will go back to thinning.
How would you introduce convexity?


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## ian (Nov 17, 2021)

beanbag said:


> How would you introduce convexity?



Thin at a slightly higher angle near the edge. Depending on how much convexity you’re going for, this can just be a difference in finger pressure — putting your fingers pretty close to the edge while you’re thinning will tend to do a bit of this.


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## beanbag (Nov 17, 2021)

ian said:


> Thin at a slightly higher angle near the edge. Depending on how much convexity you’re going for, this can just be a difference in finger pressure — putting your fingers pretty close to the edge while you’re thinning will tend to do a bit of this.


I've had my fingers close to the edge the whole time, and if the stone is flat, it pretty much results in a flat grind still.


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## Jovidah (Nov 17, 2021)

Wobble more?


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## ian (Nov 17, 2021)

beanbag said:


> I've had my fingers close to the edge the whole time, and if the stone is flat, it pretty much results in a flat grind still.



Well, obviously I don’t know exactly what’s happening with you, but steel will tend to wear away right under your fingers if you are pressing reasonably hard. So, if your fingers are near the edge, you will tend to thin just there, instead of near the shinogi line, which gives your wide bevel a bit of convexity. If you want more convexity, you can raise your angle ever so slightly. At that point it stops functioning like a wide bevel tho


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## MowgFace (Nov 17, 2021)

Still confused as to why we cant see a choil shot...

I have plenty of stamped blades that are at least reasonably represented by the choil shot.


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## beanbag (Nov 17, 2021)

MowgFace said:


> Still confused as to why we cant see a choil shot...
> 
> I have plenty of stamped blades that are at least reasonably represented by the choil shot.


Because the last time I posted a choil shot of this knife, somebody said that the edge bevel was uneven and to send it back to the manufacturer. (Which is not true - only the metal at the heel was a bit deformed from the stamping process.) Maybe once I grind thru this defect, then the choil shot will be representative.


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## Vdark (Nov 17, 2021)

Delete


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