# A Basic Explanation of Asymmetry



## Kippington

*A Basic Explanation of Asymmetry*

Way back when I began sharpening I remember reading through many forum threads about asymmetry in double bevel knives and having no idea what was going on. All this talk about 70/30 and 80/20, "You should be doing this and shouldn't do that", but no real explanation for what was actually going on. So I ignored the whole thing and went on sharpening in my 50/50 way.

A few years (and many knives) later, I realized after spending hours grinding further back behind the edge, I had developed my understanding on kitchen knives to the point where I could not only understand, but explain it in simple-enough terms. It really boils down to 3 general rules which, when understood individually, combine to explain the whole thing. 

So we'll start off with a diagram of a crappy knife, then introduce one rule at a time and improve it till we get something which represents a good knife (the rules are in random order and only numbered for ease of reading).






_Figure 1. A huge, fat, symmetrical knife_

*Rule 1 - Food releases off a curved surface better than it does off a flat surface*

Most cuts we do in the kitchen are flat, and when a flat surface on the food comes into contact with a flat surface on the side of your knife, the large amount of surface area in contact between them increases drag and can be enough to hold them together. This is known as _stickage_, and it's a pain in the ass to put up with. We can minimize this nasty effect with the use of a curve instead of a flat on the side of the knife, because there is less surface area shared between a flat and a curve (the same effect can be had with a multi-faceted compound bevel) when compared to a flat-on-flat.




_Figure 2. A curvy, fat, symmetrical knife_

*Rule 2 - The thinner the knife, the easier it moves through what it is cutting*

This is pretty much self explanatory. Thicker knives have to push more out of the way on either side as they pass through food.

But here's a problem: The thinner you make a knife, the less curve you can fit on either side. This compromises Rule 1, and so we have to balance how thin the knife is with how much stickage we are willing to put up with.
The heat-treatment and kind of steel will determine how thin you can get your knife before its strength becomes compromised.




_Figure 3. A curvy, thin, symmetrical knife_

So here we are at a nice compromise of thickness vs. curvature. Cut food falls off on either side of the knife and it's not so wide as to get wedged in the food all too often. Perfect, right?
It turns out there's another way to improve the shape even further, and it has to do with how we use kitchen knives.
When cutting food, we generally hold the knife in our dominant hand and the foodstuff in the other. Lets say you're right handed and the food is held securely in your left. Do you really need the ability for food to drop off the left side of your knife if you're already holding it down? We may as well sacrifice some of the curve on that side and make the knife thinner overall. Like so:




_Figure 4. A curvy, thin, asymmetrical knife_

This flatter surface on the left also has the added benefit of helping your left hand guide the up/down movement of the knife in a more predictable fashion.
Of course, using this little trick introduces a new problem: Steer.

*Rule 3 - Asymmetry in the grind will determine the amount of steer the user experiences*

A blade pushing through foodstuff will turn if it's getting deflected more on one side compared to the other. This asymmetry we introduced in Figure 4 has increased the amount of deflection on the right side, and as such the blade will steer towards the left (of the user).




_Figure 5. Different amounts of deflection on either side of the blade (green arrows) will cause the knife to steer off-center (red arrow)_

We can counter-act this somewhat by sharpening the knife in such a way to make it want to steer in the other direction.




_Figure 6. Asymmetrical sharpening. Note the right bevel is both shorter and more acute to the blue line when compared to the left_

If we zoom into the sharpened area you can see that the size and the angles of the bevels are uneven. This is done on purpose for two reasons: It helps steer the knife to the right, which in turn cancels out the existing steer to the left. And it also helps keep the sharp point closer in line to the middle of the blade (the blue line), which is very important in the case of clad/san-mai knives.




_Figure 7. The differing size and angle of the bevels introduce deflection in the opposite direction of Figure 5, helping to cancel out any steering overall_

So that's basically it! 
Hopefully it's not too hard to understand and helps alleviate the confusion that some people have on the topic.
I should point out that while these general rules do apply to single bevel knives, the sharpening of them is done differently to what I've shown here. No correction is done to steering on a single bevel knife.
Let me know if I've missed something.


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## HRC_64

Excellent post OP

Bumping this thread so more people see it.


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## milkbaby

Great cartoons, a picture is worth a thousand words! :doublethumbsup:


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## James

This should be stickied


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## txtrqdrt

Agreed - this is a very helpful post. Thank you Kippington :thumbsup:


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## Benuser

Excellent!


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## cyberbaton

Great job, thank you. Someone say that you should spend some time on right side and less amount of time on left side. Is it correct approach, or only angles are important?


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## Benuser

I generally have the right side as convexed as I can, and I even keep the shoulder on the left one on purpose in some extreme cases. But steering is a very individual matter. Get used to it, loosen your grip and little by little you will compensate for it and need less correction of the geometry. 
A good trick to see how the blade itself behaves is by making a cut without any pressure, only with the blade's weight in the inverse sense of your normal cutting. If you normally push, try this pulling and vice versa. See under which angle cuts the best.


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## Mute-on

I didn't even have to read any of the words to understand this. A perfect explantation of what took me ages to conceptualise earlier in my knife sharpening journey.

Many thanks!


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## GeneH

Awesome diagrams and explanation. That really makes steering issues with asymmetrical convex shapes easier to understand. And yep, not going there with any of my blades. I don't see intentional asymmetry in my future.


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## Anton

thanks for sharing and the time put into this


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## Benuser

Please be aware that good Western knives aren't either strictly symmetric. Often the left side is flatter, and the right one more convexed. See good Sabs or Herders. But off-centering the edge is indeed a change the Japanese have introduced.


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## StonedEdge

Just wanna says thanks to the OP for this, I think one of the Daves had a thread on assymetry which I can't for the life of me find again. The illustrations are spot on


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## Benuser

http://www.kitchenknifeforums.com/showthread.php/5656-Asymmetry-–-The-REAL-DEAL


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## StonedEdge

Benuser, that's the one! Thanks to you as well!


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## Benuser

My pleasure!


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## Kippington

Thanks everyone, it feels good to give a little back to the crew that taught me so much. :doublethumbsup:

Gene, you're closer to this than you think!



cyberbaton said:


> Someone say that you should spend some time on right side and less amount of time on left side. Is it correct approach, or only angles are important?



The important thing: The overall effect that each bevel and curve has on the performance of the knife.
It's up to you if you want to change it or keep it the same.


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## pd7077

Perfect explanation! Thanks for taking the time to write this up.


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## Drosophil

This is so well explained. Thank you!


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## Mute-on

cyberbaton said:


> Great job, thank you. Someone say that you should spend some time on right side and less amount of time on left side. Is it correct approach, or only angles are important?



On a double bevel knife, as illustrated here, the angles are more important. The amount of time is a byproduct of however long it takes to get your angles right :thumbsup:


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## jbeng77

This is good stuff. I fear that implementing this is going to be easier said than done. I'll work on it.


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## StonedEdge

It sounds daunting but in practice it's pretty straight forward...that said it's good to know that some j-knives don't have assymetrical bevels


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## Boynutman

So I have a question related to this. When applying a small micro bevel (a hair's width, lets say 0.1-0.2mm), would this count as a significant asymetry?
I think not... doesnt feel like it... but what are your thoughts?
I am a righty, apply my micro bevels on the rh side out of habit, but ideally these should perhaps be on the lh side. Or am I exagerating here?

To be complete, I am talking about double bevelled gyutos here.

Thanks!


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## StonedEdge

No..a micro bevel doesn't really factor into a knife's assymetry as it is at the very edge of the edge. Assymetry is mostly dealt with above the edge. Think of it as part of the primary bevel while the micro bevel is the very end part of the secondary bevel. Make sense?
Primary bevel: shoulders of the knife
Secondary: the taper leading to the actual cutting edge


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## Kippington

Boynutman said:


> When applying a small micro bevel (a hair's width, lets say 0.1-0.2mm), would this count as a significant asymetry?



Actually, this is a damn good question which touches on something I forgot to cover in my initial post.
The short answer is no, it doesn't have much of an affect. But if it does, you'll feel the knife steer off center as you cut through certain foods.

For a more detailed explanation:
Lets imagine you buy a brand new gyuto and take it out of the box. Assuming the makers have done their job correctly, the knife should not steer due to asymmetry... and importantly *it should be thin behind the edge.* 






When a knife is thin behind the edge, any bevel you set through normal sharpening will be so small as to have a tiny effect on the overall steering of the knife.
This is very important when you consider: If the maker needed to correct a problem with steer using only the tiny bevel available to them along the cutting-edge, they may have had to put an extreme angle on it to get the desired counter-steer effect.

As the end user, you might go along happily using the knife and sharpening it every so often. Lets say you don't do any thinning to the areas behind the edge - The edge bevel gains a _slight_ increase in size each time you sharpen the knife, and as a result that initially small bevel grows larger and begins to have more _and more _of an affect on the performance of the knife. Some people don't see this as a problem and allow it to spiral out of control.






What happens if you stick to the extreme asymmetric sharpening angle that was on the knife out of the box? As you can imagine, the magnified counter-steer effect of the larger bevel grows disproportionately to the asymmetry behind the edge, resulting in an over-correction to the steer.
The best way to deal with this is to *THIN YOUR KNIFE! Fat edges are bad, mmmkay?* :spankarse:
But if this is too advanced for you to attempt (or maybe you don't have the time or equipment), you'll need to make up for it by adjusting the asymmetry of the edge bevels. You can do this if you feel the knife starting to steer off-center during normal use by slightly changing the sharpening angles the next time you take the knife to the stones. Just be aware that if you get the knife thinned later on, you may have to revert back to the original sharpening asymmetry.


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## HRC_64

mods really need to sticky this thread !


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## Bolek

Kippington said:


> *A Basic Explanation of Asymmetry*
> 
> Way back when I began sharpening I remember reading through many forum threads about asymmetry in double bevel knives and having no idea what was going on. All this talk about 70/30 and 80/20, "You should be doing this and shouldn't do that", but no real explanation for what was actually going on. So I ignored the whole thing and went on sharpening in my 50/50 way.
> 
> A few years (and many knives) later, I realized after spending hours grinding further back behind the edge, I had developed my understanding on kitchen knives to the point where I could not only understand, but explain it in simple-enough terms. It really boils down to 3 general rules which, when understood individually, combine to explain the whole thing.
> 
> So we'll start off with a diagram of a crappy knife, then introduce one rule at a time and improve it till we get something which represents a good knife (the rules are in random order and only numbered for ease of reading).
> 
> 
> 
> 
> 
> _Figure 1. A huge, fat, symmetrical knife_
> 
> *Rule 1 - Food releases off a curved surface better than it does off a flat surface*
> 
> Most cuts we do in the kitchen are flat, and when a flat surface on the food comes into contact with a flat surface on the side of your knife, the large amount of surface area in contact between them increases drag and can be enough to hold them together. This is known as _stickage_, and it's a pain in the ass to put up with. We can minimize this nasty effect with the use of a curve instead of a flat on the side of the knife, because there is less surface area shared between a flat and a curve (the same effect can be had with a multi-faceted compound bevel) when compared to a flat-on-flat.
> 
> 
> 
> 
> _Figure 2. A curvy, fat, symmetrical knife_
> 
> *Rule 2 - The thinner the knife, the easier it moves through what it is cutting*
> 
> This is pretty much self explanatory. Thicker knives have to push more out of the way on either side as they pass through food.
> 
> But here's a problem: The thinner you make a knife, the less curve you can fit on either side. This compromises Rule 1, and so we have to balance how thin the knife is with how much stickage we are willing to put up with.
> The heat-treatment and kind of steel will determine how thin you can get your knife before its strength becomes compromised.
> 
> 
> 
> 
> _Figure 3. A curvy, thin, symmetrical knife_
> 
> So here we are at a nice compromise of thickness vs. curvature. Cut food falls off on either side of the knife and it's not so wide as to get wedged in the food all too often. Perfect, right?
> It turns out there's another way to improve the shape even further, and it has to do with how we use kitchen knives.
> When cutting food, we generally hold the knife in our dominant hand and the foodstuff in the other. Lets say you're right handed and the food is held securely in your left. Do you really need the ability for food to drop off the left side of your knife if you're already holding it down? We may as well sacrifice some of the curve on that side and make the knife thinner overall. Like so:
> 
> 
> 
> 
> _Figure 4. A curvy, thin, asymmetrical knife_
> 
> This flatter surface on the left also has the added benefit of helping your left hand guide the up/down movement of the knife in a more predictable fashion.
> Of course, using this little trick introduces a new problem: Steer.
> 
> *Rule 3 - Asymmetry in the grind will determine the amount of steer the user experiences*
> 
> A blade pushing through foodstuff will turn if it's getting deflected more on one side compared to the other. This asymmetry we introduced in Figure 4 has increased the amount of deflection on the right side, and as such the blade will steer towards the left (of the user).
> 
> 
> 
> 
> _Figure 5. Different amounts of deflection on either side of the blade (green arrows) will cause the knife to steer off-center (red arrow)_
> 
> We can counter-act this somewhat by sharpening the knife in such a way to make it want to steer in the other direction.
> 
> 
> 
> 
> _Figure 6. Asymmetrical sharpening. Note the right bevel is both shorter and more acute to the blue line when compared to the left_
> 
> If we zoom into the sharpened area you can see that the size and the angles of the bevels are uneven. This is done on purpose for two reasons: It helps steer the knife to the right, which in turn cancels out the existing steer to the left. And it also helps keep the sharp point closer in line to the middle of the blade (the blue line), which is very important in the case of clad/san-mai knives.
> 
> 
> 
> 
> _Figure 7. The differing size and angle of the bevels introduce deflection in the opposite direction of Figure 5, helping to cancel out any steering overall_
> 
> So that's basically it!
> Hopefully it's not too hard to understand and helps alleviate the confusion that some people have on the topic.
> I should point out that while these general rules do apply to single bevel knives, the sharpening of them is done differently to what I've shown here. No correction is done to steering on a single bevel knife.
> Let me know if I've missed something.


In practice how sharpen a 50/50 knife to a asymmetry of fig 7 ?


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## Boynutman

@kippington and Stonededge, thanks! That makes a lot of sense, never really considered the thickness behind the edge issue and how growing bevels may magnify steering.


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## Kippington

No problem, glad to help.



HRC_64 said:


> mods really need to sticky this thread !



It would be cool if they could do that! :biggrin:



Bolek said:


> In practice how sharpen a 50/50 knife to a asymmetry of fig 7 ?



When you sharpen the left side, lift the spine a little higher off the stone. Have the spine closer to the stone on the right side, and use slightly fewer strokes.


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## Bolek

Thanks. Will try.


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## Benuser

U


Bolek said:


> Thanks. Will try.



What kind of knife is concerned?


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## Bolek

Benuser said:


> U
> 
> What kind of knife is concerned?


First atempt will be made on a valuless SS quite sharp and fine behind the edge butcher knife. If it is a succes then a blue 2 Zakuri gyuto.


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## Valkyrae

Really excellent post. First time I've seen a good explanation of why asymmetry might be a beneficial thing, and not just a product of the craftsmen having a right-hand bias!


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## HRC_64

Bolek said:


> First atempt will be made on a valuless SS quite sharp and fine behind the edge butcher knife. If it is a succes then a blue 2 Zakuri gyuto.



Are you trying to thin the grind or correct steering?


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## woodworkcan

Very interesting.
Has anyone tried the grind like in figure 7 on traditional single-bevel knives?
I have never seen someone grind the ura like that before.


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## tripleq

woodworkcan said:


> Very interesting.
> Has anyone tried the grind like in figure 7 on traditional single-bevel knives?
> I have never seen someone grind the ura like that before.



The uraoshi of a traditional knife is slightly concave and meant to be sharpened flat. There is precious little metal to work with for adding bevels. Some people put micro bevels on the heel of the uraoshi for strength on debas but it isn't wise to go further than that. In order to put a grind like # 7 on a single bevel you'd have to grind the uraoshi to the point of negating the design and/or ruining the knife completely.


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## woodworkcan

tripleq said:


> The uraoshi of a traditional knife is slightly concave and meant to be sharpened flat. There is precious little metal to work with for adding bevels. Some people put micro bevels on the heel of the uraoshi for strength on debas but it isn't wise to go further than that. In order to put a grind like # 7 on a single bevel you'd have to grind the uraoshi to the point of negating the design and/or ruining the knife completely.



That is also my concern and my understanding of the single-bevel design. And why I don't want to try with my "nice" knives.


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## DanDan

So the general fix for unwanted steering is to thin the blade? What if you've been doing light thinning before every sharpening (low-angle) and notice steering while cutting? A more intense thinning is warranted then?

Now for probably a silly question (and I'm not sure how to word it correctly): If I'm a lefty, and I'm just sharpening regularly (without any notice to asymmetry), can it have negative consequences if I hand it to a righty? i.e. Could I cause steering to the left just as a consequence of sharpening naturally as a lefty?


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## Benuser

For a part steering is an individual question. It depends partially on your grip and the orientation of your wrist. Some people can compensate huge steering, without being aware of it anymore. Find out under which angle the blade performs the best. Try cutting by pulling without any pressure and see which inclination the blade takes.
Thinning equally both sides behind the edge will reduce steering, not eliminate it. 
If it steers clockwise, you may reduce the friction on the right side or increase it on the left side, by taking a higher sharpening angle. Probably you should do both.
For steering anti-clockwise do the opposite: thin the left side and increase the right angle.


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## Kippington

DanDan said:


> So the general fix for unwanted steering is to thin the blade? What if you've been doing light thinning before every sharpening (low-angle) and notice steering while cutting? A more intense thinning is warranted then?


It's hard to say without seeing the knife in person, but perhaps you have been thinning the bevel at a different angle from the original grind - or as you say, too light of a thinning. In this case a more intense thinning would work, if done only to the opposite side from the direction your blade is steering towards.







But do it too much and you might end up with a symmetrical grind.



DanDan said:


> Could I cause steering to the left just as a consequence of sharpening naturally as a lefty?


Your sharpening _technique _will have more of an influence over the steer, rather than your use of either the left or right hand.


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## TEWNCfarms

Kippington said:


> Actually, this is a damn good question which touches on something I forgot to cover in my initial post.
> The short answer is no, it doesn't have much of an affect. But if it does, you'll feel the knife steer off center as you cut through certain foods.
> 
> For a more detailed explanation:
> Lets imagine you buy a brand new gyuto and take it out of the box. Assuming the makers have done their job correctly, the knife should not steer due to asymmetry... and importantly *it should be thin behind the edge.*
> 
> 
> 
> 
> 
> 
> When a knife is thin behind the edge, any bevel you set through normal sharpening will be so small as to have a tiny effect on the overall steering of the knife.
> This is very important when you consider: If the maker needed to correct a problem with steer using only the tiny bevel available to them along the cutting-edge, they may have had to put an extreme angle on it to get the desired counter-steer effect.
> 
> As the end user, you might go along happily using the knife and sharpening it every so often. Lets say you don't do any thinning to the areas behind the edge - The edge bevel gains a _slight_ increase in size each time you sharpen the knife, and as a result that initially small bevel grows larger and begins to have more _and more _of an affect on the performance of the knife. Some people don't see this as a problem and allow it to spiral out of control.
> 
> 
> 
> 
> 
> 
> What happens if you stick to the extreme asymmetric sharpening angle that was on the knife out of the box? As you can imagine, the magnified counter-steer effect of the larger bevel grows disproportionately to the asymmetry behind the edge, resulting in an over-correction to the steer.
> The best way to deal with this is to *THIN YOUR KNIFE! Fat edges are bad, mmmkay?* :spankarse:
> But if this is too advanced for you to attempt (or maybe you don't have the time or equipment), you'll need to make up for it by adjusting the asymmetry of the edge bevels. You can do this if you feel the knife starting to steer off-center during normal use by slightly changing the sharpening angles the next time you take the knife to the stones. Just be aware that if you get the knife thinned later on, you may have to revert back to the original sharpening asymmetry.



This is a really informative thread, thanks! So what would a Correctly sharpened knife/bevel look like? Since you showed the bevel that was sharpened too much/high. Also do you have a video or can link a video showing these exact methods to obtain a good food release asymmetry? Ive followed the Korin videos and others and thought I was doing a 70/30 right, but after reading this I question it now, also the new Masashi I have is supposed to have good food release and I didnt use it before sharpening and I wonder if I didnt achieve the asymmetry like I hoped.


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## zetieum

moderators: stick this post!

Thanks for effort of making the schemes and thx for sharing it: Invaluable!


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## Kippington

Thanks zetieum!

TEWNCfarms, I believe you've misunderstood the concept. There are two distinctly separate parts to this:






If you are only messing around with asymmetrical sharpening, you'll never get better food release off the existing grind.
In the original post I go all the way to figure 5 without talking about sharpening. Only once we get to 6 and 7 does it get introduced.
So tell me - have you been playing around with just the sharpening, or have you been modifying the grind as well?


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## TEWNCfarms

Kippington said:


> Thanks zetieum!
> 
> TEWNCfarms, I believe you've misunderstood the concept. There are two distinctly separate parts to this:
> 
> 
> 
> 
> 
> 
> If you are only messing around with asymmetrical sharpening, you'll never get better food release off the existing grind.
> In the original post I go all the way to figure 5 without talking about sharpening. Only once we get to 6 and 7 does it get introduced.
> So tell me - have you been playing around with just the sharpening, or have you been modifying the grind as well?



Ahhh I see ! Thanks for the response! Ive Only been doing the sharpening not the grind. I dont really know how I would go about changing the grind. And the grind on the Masashi is pretty good from what I can tell, so I dont want to start hacking away at it and mess it up you know...


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## Benuser

I hope you start your sharpening behind the edge with a bit of thinning. Or you end in no time with a great looking poor cutter. Let the bevel be in line with the face.


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## TEWNCfarms

Benuser said:


> I hope you start your sharpening behind the edge with a bit of thinning. Or you end in no time with a great looking poor cutter. Let the bevel be in line with the face.



What exactly do you mean in line with the face? And do you mean I need to thin it before I start sharpening?! Thanks for your help!


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## Benuser

Try to let the right, convex side flow into the bevel, as to form a continuous arc.
Yes, you're moving a previous configuration to a slightly thicker part of the blade. 
Some very common figures for a chef's knife: just above the edge, thickness is 0.2mm. At 5mm from there 0.5mm. At 10mm about 1mm.
If you don't thin when sharpening performance will rapidly decrease, and a Herder will turn into a Wüsthof within a year.


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## Kippington

Benuser said:


> Try to let the right, convex side flow into the bevel, as to form a continuous arc.



Cool way of phrasing it! :doublethumbsup:


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## TEWNCfarms

Benuser said:


> Try to let the right, convex side flow into the bevel, as to form a continuous arc.
> Yes, you're moving a previous configuration to a slightly thicker part of the blade.
> Some very common figures for a chef's knife: just above the edge, thickness is 0.2mm. At 5mm from there 0.5mm. At 10mm about 1mm.
> If you don't thin when sharpening performance will rapidly decrease, and a Herder will turn into a Wüsthof within a year.



Awesome I appreciate the help


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## Benuser

My pleasure.


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## TEWNCfarms

Benuser said:


> Try to let the right, convex side flow into the bevel, as to form a continuous arc.
> Yes, you're moving a previous configuration to a slightly thicker part of the blade.
> Some very common figures for a chef's knife: just above the edge, thickness is 0.2mm. At 5mm from there 0.5mm. At 10mm about 1mm.
> If you don't thin when sharpening performance will rapidly decrease, and a Herder will turn into a Wüsthof within a year.



Is there a specific way to thin so I make it arc better? Or just slowly thin going up. Again Im just so afraid to mess up the original convex you know. I do love this Masashi, its really interesting to feel the difference with the Gekko ktip which is Much thinner and flat


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## Benuser

Nothing to dramatise. We're speaking here about perhaps the last two millimetres before the edge, which has perhaps a width of half of a millimetre. Forget the idea of a clear, pronounced bevel. That's only fine for the makers of poor EDCs. Easy to make and impress the public, but not very effective as far as cutting is concerned. I would start by removing the shoulder, and find out at which minimal angle you still feel comfortable. Make a scratching move perpendicular to the edge, and raise the spine little by little until you've reached the angle at which you raise a clear burr on the opposite side.
Or, instead of short scratching moves, make the more conventional move along the edge, and again, raise the spine little by little. See your progress by verifying the scratch pattern with a loupe, or use the Marker Trick. 
I guess you know Mr Broida's excellent videos on YouTube. 
Don't be afraid, it's no high tech. Until the twenties everybody sharpened his own razor. Until much more recently everybody on the countryside sharpened his own tools. 
You need a lot of effort, time and powered tools to make errors who cannot easily be repaired. Others only need a bit of explanation. 
We don't ask you to rebuild an entire blade. Just to restore a previous configuration that has moved a fraction of a millimetre.


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## TEWNCfarms

Benuser said:


> Nothing to dramatise. We're speaking here about perhaps the last two millimetres before the edge, which has perhaps a width of half of a millimetre. Forget the idea of a clear, pronounced bevel. That's only fine for the makers of poor EDCs. Easy to make and impress the public, but not very effective as far as cutting is concerned. I would start by removing the shoulder, and find out at which minimal angle you still feel comfortable. Make a scratching move perpendicular to the edge, and raise the spine little by little until you've reached the angle at which you raise a clear burr on the opposite side.
> Or, instead of short scratching moves, make the more conventional move along the edge, and again, raise the spine little by little. See your progress by verifying the scratch pattern with a loupe, or use the Marker Trick.
> I guess you know Mr Broida's excellent videos on YouTube.
> Don't be afraid, it's no high tech. Until the twenties everybody sharpened his own razor. Until much more recently everybody on the countryside sharpened his own tools.
> You need a lot of effort, time and powered tools to make errors who cannot easily be repaired. Others only need a bit of explanation.
> We don't ask you to rebuild an entire blade. Just to restore a previous configuration that has moved a fraction of a millimetre.



Ohh okay I see what youre saying, thanks so much! I actually have a lens magnifier for my phone I completely forgot about, I can use that. Haha and yeah youre right on that I didnt even really think about that that everyone sharpened their own tools and stuff. Thanks for the great information


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## Benuser

You're most welcome.


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## Gjackson98

always a pleasure to read your posts.


----------



## masibu

This is gonna be a long post but im trying to put all the info in I can think of so I can hopefully get some answers.

Looking through this thread im getting the idea that the bevel should appear to be wider on the left hand side despite being sharpened at a higher angle than the right and should also take more strokes to sharpen than the right hand side. I've received blades that have appeared to have been assymetrically sharpened (misono and especially sugimoto come to mind but there are probably others) but the wider bevel is on the right hand side than the left and these were for a right hander (that being me).

I have been using a lower angle on the right hand side than the left but it takes me roughly twice as long on the right hand side compared to the left to maintain this assymetry of keeping the bevel wider on the right hand side (thinning as necessary/when I can be bothered). Is this the incorrect approach? Should i be going to town on the left hand side until the apex shifts over closer to the right so I end up with a larger bevel on the left hand side than the right?

I haven't had any issues doing it the way I have been and do notice a small decrease in food drop off since i started sharpening this way instead of the usual 50/50 that i was doing for years. It seems to be more in line to what the makers of these knives did which was why I took this approach but I could be horribly wrong. I haven't noticed any issues by doing it the way I have but then I've never handled a knife that has been sharpened by someone else that I've been impressed with. Thats not to come across as arrogant but rather a lot of chefs or butchers ive happened to come across barely know how to sharpen/dont do it at all or barely get it done frequently enough. I've been teaching myself the whole way wading through pages of (mis)information and youtube videos and correcting myself along the way.

Also, regarding the microbevel.. is there any advantage to applying it on one side vs the other? Should I apply a 50/50 micro bevel on an assymetric edge (possibly sharpening more on one side than the other)? Should I be applying an assymetric micro bevel if I'm sharpening assymetrically? Am I asking too many questions?

I have been playing around with different microbevels recently but not enough to comment seriously. For example a massive angled left side only micro bevel with the right side at edge angle seemed to shave my right arm at a really low angle compared to the left. This is assuming im using the same blade sharpened in the same manner I mentioned earlier. I didnt cut anything with it unfortunately but im wagering that the food release would be even better on the right hand side of the knife. However I'm unsure whether that would also sacrifice durability by keeping the apex so assymetric? I back bevel the same assymetric edge bevels after microbevelling which seems to reduce the influence of the micro bevel anyway so I really have no idea what the "correct" approach is. FWIW I have been primarily setting microbevels assymetrically for the sake of it as opposed to either 50/50 or on one side only as it just seemed like a safe bet.

Sorry for the long winded post but I guess I'm trying to make sure that I'm heading down the right track


----------



## Kippington

Firstly, please take a look at the most recent picture posted above. Your post mentions small (perhaps even negligible?) changes to food drop off from your modifications... but from what I can tell, you've only been talking about variations in asymmetrical sharpening, and you haven't made any changes to the asymmetry of the grind. Could this be the case?

If you're only talking about sharpening, the answers to your questions will always revolve around the specific grind of the knife you're sharpening. For example, if you're experiencing no steering issues at all, there'd be no reason to change your sharpening bevels from their current angles and sizes.

As for micro-bevels - they're an interesting topic because they have a lot to do with how the knife in question is intended to be used.
Micro-bevels are so small that they don't affect food release, meaning for this consideration it hardly matters which side they go on. They are, however, _very important_ to blade usage and edge retention. Gyutos and chef's knives are used mostly in an up-and-down orientation (perpendicular to the board), so I'd want to have the micro-bevel done to the side that has the shallower angle (in our diagrams, the right side). Doing it like this would increase the chances of the edge hitting the cutting-board dead on, as opposed to side on (at an angle).

But importantly, this whole dynamic changes once you have a knife that is designed to run alongside something that isn't supposed to be cut - for example, shaving razors which run along skin, or honesuki that run along bones. As you found with shaving arm hair, in these scenarios you're much better off with the micro-bevel on the opposite side of the blade from the side which contacts the material that isn't to-be-cut. This aids in keeping the edge flush to where it needs to be and allows less material to get in-between the blade and the surface it rides up against.

This also follows through to single-bevel blades. Imagine what would happen if you had a micro-bevel on the flat (read:_wrong_) side of a chisel. It would throw the chisel off being 'true' causing it to wonder off (much like in the bottom right picture). It would also play long-term havoc on the resharpenablility of the flat side.


----------



## Benuser

Thanks for the chisel analogy!


----------



## masibu

Yeah im strictly speaking from a sharpening perspective only, no altering of the grind at all. The food drop off was fairly minor (not that I was expecting much of a change at all). I haven't noticed any steering with any knives but then I'm probably so used to it that if there were steering problems I've probably adjusted naturally anyway. I can only recall it ever being an issue many years ago with a yoshikane skd (regret selling that knife away!) To which I thinned it out dramatically and changed the bevels to what was probably 50/50 at the time.

Ive been happy with the edges I've been getting since changing my method as it seems a lot faster than what I was doing (although it took a bit of getting used to regularly having uneven bevel sizes at first) but wasn't sure if I was taking the right approach and whether by doing that it may have negative effects on performance at some point eg edge retention and resistance to damage.

Sharpening 50/50 with micro bevels was straight forward as i kept them the same for each side but im trying to visualize the edge assymetrically and my head gets a bit topsy turvy with ideas for what would work best. It would seem that ive been doing the reverse of what has been recommended here by applying a higher angled micro bevel to the left side compared to the right? It hasnt posed a problem so far but then again my bevels are shorter (is this what you mean by shallower or are you referring to angle?) And have obtuse angles on the left side for the vast majority of my knives compared to the right. I guess its something to tinker with for the time being.

Cheers for explaining that and the pictures. I will probably stare at them some more whilst i decide whether I want to reprofile another knife to compare with what ive been doing


----------



## Kippington

No problem!


masibu said:


> ...my bevels are shorter (is this what you mean by shallower or are you referring to angle?)...


I can see why this is confusing.
The terms *'shallow' *_(acute)_ and *'obtuse'* are directly related to sharpening angles. The descriptors 's_hallow_' and '_higher_' are used for angle because of how we hold the spine at a certain height from the stone while sharpening.
The terms *'short'* and _*'wide'* (long)_ refer to the length of surface area the bevel covers as it moves up the blade face. Some people use time on the stones as an indicator for short or long bevels (e.g. "sharpen twice as many strokes on the left side") but this is actually a terrible way of describing surface area, as it holds little regard for both the condition of the blade prior to sharpening and the angles being used. For example, grinding a shallow angle over an obtuse one can take a lot of time, but reversing it takes seconds.


masibu said:


> I haven't noticed any steering with any knives but then I'm probably so used to it that if there were steering problems I've probably adjusted naturally anyway.


If you're happy with your knifes' performance, changing up your angles would most likely be causing it more harm than good.
If you want to understand asymmetry better, perhaps you can find a knife with a related problem and work to improve it from there. If it ain't broke, don't fix it! 
People tend to show the methods of asymmetric sharpening without describing the reasons behind doing it - this can lead to presumptions, overthinking and overall confusion on behalf of the listeners. For example, this video pretty much explains it as a cultural thing! 
My hope is that this thread educates people on _why _asymmetry is done, and how it affects the overall performance of the blade. Then it's up to you to decide how to go about achieving those results.


----------



## masibu

Before I get into my post, just wanna be clear that I'm referring more to edge strength than I am to steering although I would assume there may be a difference in the way our knives cut



Kippington said:


> No problem!
> 
> I can see why this is confusing.
> The terms *'shallow' *_(acute)_ and *'obtuse'* are directly related to sharpening angles. The descriptors 's_hallow_' and '_higher_' are used for angle because of how we hold the spine at a certain height from the stone while sharpening.
> The terms *'short'* and _*'wide'* (long)_ refer to the length of surface area the bevel covers as it moves up the blade face. Some people use time on the stones as an indicator for short or long bevels (e.g. "sharpen twice as many strokes on the left side") but this is actually a terrible way of describing surface area as it holds little regard for both the condition of the blade prior to sharpening and the angles being used (e.g. grinding a shallow angle over an obtuse one can take a lot of time, but doing the reverse takes seconds).



I figured you were referring to shallower angles but I think what I was trying to confirm was whether the microbevel is put on the right hand side in your case is because of the shallower angle or because of the shorter bevel on the right hand side. I'm assuming from the pictures that you're grinding more on the left hand side at an obtuse angle (compared to the right hand side) and also developing taller bevels. I would assume that sharpening this way would lead to the apex favouring the right hand side in your case and the micro bevel on the right hand side would then be beneficial to centre it/straighten it more and strengthen it?

I'm going back to that chisel analogy though now and the microbevel is put on the wider bevel, which is the opposite to what you're doing? However that is single edged and different to a knife. In my case the apex is going to slightly favour the left hand side (but at a shallower angle in comparison I would assume than with your knife as i sharpen the right side at a lower angle) and so it probably would make more sense to microbevel the left hand side.

I'm curious because if I'm using the shallower angle on the right hand side (but the bevels are wider), would it be more beneficial to micro bevel both sides (smaller angles than I would if applying it to just the one side) compared to applying it to just one side? Looking back at that chisel again (and realising that my edge probably starts to resemble a chiselesque edge although not as extreme) I'm questioning whether I should be microbevelling the shallow angled and wider right bevel and then end up going round in circles.

Again thanks for the response. At this point I guess im obsessing over the details and I would probably benefit from trying your method on another knife just to compare differences


----------



## Kippington

To put it simply, I'd suggest that the micro-bevel on a gyuto is done in such a way that the very edge has roughly the same angle on the left side as the right - Remember: this is talking about the micro-bevel only, a small hairline of a thing. Doing it this way completely ignores (or has nothing to do with):

Centering the edge directly below the middle of the spine

How short or wide the bevels are on either side
Steering
Food release
The micro bevel is too small to really affect any of these.

We tend to do it on whichever side has the more acute bevel of the two, and in doing so builds more reinforcement behind whichever side has the shallower angle - generally the right side for a right handed asymmetry. This helps increase edge retention.
Remember, this only applies to a knife designed for mostly up and down work, perpendicular to a cutting board surface. As I mentioned earlier, this rule would reverse if you're dealing with a single bevel knife, or a double bevel that was designed to ride up accurately against a material or mark that you don't want to cut into.

Clear as mud?


----------



## masibu

Alright sweet as, I was taking that approach originally and started over analysing it trying to figure out the principle of it all. Definitely have more confidence in what im doing now, cheers.


----------



## Kippington

My pleasure!


----------



## DainBramage1

Interesting stuff! A couple questions:
1. Is half convex the way a 70/30 or other would come from from a manufacturer, or is this purely custom and/or done after purchase?
2. I hope i didn't miss it, but what is your preferred method for sharpening/creating the convex side?

Thanks!


----------



## chinacats

I'll let Kip respond but throw out the fact that most everything from Japan is asymmetrical...but add a link for some further reading...

https://www.kitchenknifeforums.com/threads/asymmetry--the-real-deal.5656/


----------



## Kippington

DainBramage1 said:


> 1. Is half convex the way a 70/30 or other would come from from a manufacturer, or is this purely custom and/or done after purchase?


It can be done many ways. Half convex, full convex, S-grinds, sabre grinds (wide bevels) and even concave grinds are all possible ways to get a 70/30. Manufacturers can use any of these, but will mostly use convex as it is the easiest to do.
Here's an example (from marc4ptoknives on Instagram) of a Tanaka Kyuzo Migaki. It has a 70/30 grind which is clearly _not _convexed, but instead a concave wide-bevel.








DainBramage1 said:


> 2. I hope i didn't miss it, but what is your preferred method for sharpening/creating the convex side?


Slack belts are pretty boss for convex, but it can be done by hand on a stone too. Doing it well involves a lot of back and-forth-testing, for the first few times at least.

I should mention that its not a good idea to use the belt for sharpening... it's for doing the grind.
A kitchen knife which is properly thin behind the edge will have small edge bevels, so hand sharpening will only take a couple of minutes at most.


----------



## DainBramage1

Kippington said:


> It can be done many ways. Half convex, full convex, S-grinds, sabre grinds (wide bevels) and even concave grinds are all possible ways to get a 70/30.



Thanks! One more question… can you think of any reasons not to turn a 50/50 (Tojiro DP 240mm) asymmetrical?


----------



## Kippington

If you post a choil shot I can give you a decent answer.
Without it I'm kinda in the dark.


----------



## DainBramage1

Kippington said:


> If you post a choil shot I can give you a decent answer.
> Without it I'm kinda in the dark.



As I was taking this, I realized this stock may be too thin to do this, yes?


----------



## Benuser

DainBramage1 said:


> Thanks! One more question… can you think of any reasons not to turn a 50/50 (Tojiro DP 240mm) asymmetrical?


Tojiro DP are asymmetric as any Japanese knife. With the right side, follow that face's grind. On the left one, do what is needed to make steering acceptable to you.


----------



## Kippington

DainBramage1 said:


> As I was taking this, I realized this stock may be too thin to do this, yes?
> 
> View attachment 54011


I'm not sure, its too blurry haha! 

What Benuser said should work just fine.


----------



## dgib7994

Kip - thanks for your diagrams, pictures and the wealth of knowledge in this thread. Awesome!

I have an asymmetrically ground and sharpened komakiri, its just a bit thick in general for me. The release is noticable, though


----------



## thirsty0ne

You make it look easy mate! Thx for the post...


----------



## stephen129

In the original post it mentions the edge being curved to reduce sticktion. If you've worn away a decent amount of your knife, how do you recreate an edge that is curved with stones? It would make a flat edge no?


----------



## lemeneid

stephen129 said:


> In the original post it mentions the edge being curved to reduce sticktion. If you've worn away a decent amount of your knife, how do you recreate an edge that is curved with stones? It would make a flat edge no?


There are a few ways to maintain convexity. One would be to rock the blade Murray Carter style. The other would be to use a worn down stone with a curve in it.


----------



## M1k3

Another is sandpaper on a mousepad.


----------



## labor of love

lemeneid said:


> There are a few ways to maintain convexity. One would be to rock the blade Murray Carter style. The other would be to use a worn down stone with a curve in it.


Does he have a video for this technique?


----------



## M1k3




----------



## labor of love

That’s a great video. First time I’ve heard of this. thanks


----------



## Byphy

M1k3 said:


> Another is sandpaper on a mousepad.



That's a creative method, sounds cool


----------



## M1k3

Byphy said:


> That's a creative method, sounds cool



Got it from the pocket knife community.


----------



## lemeneid

M1k3 said:


> Another is sandpaper on a mousepad.


is there a vid of this too?


----------



## stephen129

M1k3 said:


>



Ah, interesting. So is this how I should be thinning my knives? Or is it only of it had a convex grind to start with?


----------



## Carl Kotte

stephen129 said:


> Ah, interesting. So is this how I should be thinning my knives? Or is it only of it had a convex grind to start with?



Well, perhaps it depends on your goals. I like thin knives and do not care about convexity until the end of the process. Then I make sure there’s a nice convexity (for less wedging).
But if you want to restore original geometry as closely to the original as possible perhaps the wobble movement is the way to go?!


----------



## M1k3

All depends. I use a version of Jon at JKI single bevel sharpening (hamaguri) for thinning and sharpening. But this convex way Murray Carter is doing is a viable option.


----------



## M1k3

lemeneid said:


> is there a vid of this too?



Not that I could find.


----------



## M1k3

Best I could find.


----------



## Benuser

Carl Kotte said:


> Well, perhaps it depends on your goals. I like thin knives and do not care about convexity until the end of the process. Then I make sure there’s a nice convexity (for less wedging).
> But if you want to restore original geometry as closely to the original as possible perhaps the wobble movement is the way to go?!


Unless you're using a very coarse stone and huge pressure convexity of the bevel comes almost by itself when different angles are being used. Blending requires only a single stroke. Facetting is only a problem with jig users. Check with your nail.
I apply Carter's rocking motion with some pressure on a charged rough split leather with a hard wooden backing. With simple carbons it contributes to the convexity. Stay behind the very edge. End with light edge stropping to clean up from the debris you have moved to it.


----------



## ian

Benuser said:


> Facetting is only a problem with jig users.



I assume this comment is about normal wide bevel sharpening or light thinning?

I did some major 2-angle thinning of the blade face (couple hours on an atoma 140 and Gesshin 400) on this Mizuno I have a couple weeks ago, and while there were no *sharp* facets at the end, I still felt the geometry was a bit more polygonal than I liked until I did a bunch of rocking strokes. Now it’s mind blowingly awesome.

Edit: I think I misread @Benuser’s first sentence as not applying to the rest of his post. So, +1 to everything he said, as usual.


----------



## HRC_64

I think its oversimple to think a couple strokes will turn a scandi V into a "convex" edge.

A real convex edge has metal where the V has already removed it, so "taking more metal away" 
by blending V facets doesn't correct this problem...

Hope this makes sense, but this is why the mouspad etc work...
you neve get the V to start with that way...you have real convex.

Similar as you would never say a clamshell-sharpened double bevel (or single bevel),
is a "convex" grind in general (and not a wide bevel variation, etc)

the edge rolling style works also, though similarly... it helps to not over flatten ("V") the edge
before you start applying the method.

just my $0.02


----------



## Southpaw

My title for this post

“yet another reason it sucks to be left handed”


----------



## Benuser

Southpaw said:


> My title for this post
> 
> “yet another reason it sucks to be left handed”


No. 'Why left-handers better have their own knives'. Instead of looking for knives that are sub-optimal to everybody, better have a look at those with an inverted geometry. Very common ones are available with Masahiro and Misono. Left face convexed, right one flat, edge off-centered to the right.


----------



## ian

Still sucks to be a lefty (I imagine), because it's so much harder to acquire lefty knives by your favorite maker...


----------



## M1k3

Southpaw said:


> My title for this post
> 
> “yet another reason it sucks to be left handed”





ian said:


> Still sucks to be a lefty (I imagine), because it's so much harder to acquire lefty knives by your favorite maker...


But if you have @CiderBear buy it, it'll be left handed.


----------



## Southpaw

Benuser said:


> No. 'Why left-handers better have their own knives'. Instead of looking for knives that are sub-optimal to everybody, better have a look at those with an inverted geometry. Very common ones are available with Masahiro and Misono. Left face convexed, right one flat, edge off-centered to the right.


My Masamoto is left handed, it is conveyed for my side lol but the KS is so damn sticky it doesn’t matter. I hear polishing them helps, or maybe I’ll just sharpen it to the point where it starts to be convexed, so it’ll be a 240 yani by that point

trouble with that is if I want a lefty one that if you want a high quality lefty knife you have to pay 50% more for it a lot of the time.


----------



## Southpaw

M1k3 said:


> But if you have @CiderBear buy it, it'll be left handed.



maybe me and @CiderBear should get married and register at CKTG


----------



## CiderBear

Southpaw said:


> maybe me and @CiderBear should get married and register at CKTG


Deal


----------



## soigne_west

The thing I don’t get is the mark up for left handed grinds.


----------



## esoo

soigne_west said:


> The thing I don’t get is the mark up for left handed grinds.



This. 50% more for a lefty single bevel knife sucks.


----------



## ian

I have no idea about 50%, but a markup doesn't seem unreasonable if they're used to grinding right handed knives all the time. I mean, maybe it does take them significantly longer to grind it. And maybe they're more likely to screw up and have to fix the mistake. I don't know. Wish it was otherwise, though, for the sake of you good people. Hopefully karma will give us a great sharpener who only grinds for lefties...


----------



## labor of love

You’re paying a right handed person to make the left handed version of what is essentially a right handed knife(single bevels).
I’m pretty sure the ONLY reason they even make them at all is that some guys are willing to cough up the dough.


----------



## Kippington

Left-handed people get charged a devils tax





It's only fair, you guys are so damn good at everything...


----------



## M1k3

Kippington said:


> Left-handed people get charged a devils tax
> 
> 
> 
> 
> It's only fair, you guys are so damn good at everything...


Having a lefty work on my left side was pretty cool. This "new" right handed guy on my right side, sucks. He has lots of "first day" moments. Not that this advances the conversation....


----------



## nexus1935

Wow thanks so much for this super clear explanation in a few simple diagrams! I've been reading about those asymmetrical grinds for so long, but didn't realize that they were intended to offset the steer.


----------



## Kippington

nexus1935 said:


> Wow thanks so much for this super clear explanation in a few simple diagrams! I've been reading about those asymmetrical grinds for so long, but didn't realize that they were intended to offset the steer.


No problem!

-----------

There's something obvious which I should've added to the original post - Steering during a cut can increase stickage on a concave surface.

If we imagine a knife is steering to the left (like in the following picture), a slice of food on the right side will cut into a curve which is much more likely to stick to the a convexed surface of the knife. With a larger curve-on-curve contact area, this can act to reduce the advantage of a convex grind.


----------



## Benuser

What happens with food release if I try to compensate for steering by holding the knife slightly clockwise inclined?


----------



## Kippington

Benuser said:


> What happens with food release if I try to compensate for steering by holding the knife slightly clockwise inclined?


Depends on the grind and the resulting steer.


----------



## cotedupy

A quick q.- I have a cheap Deba, which to be honest I'm unlikely to use for any particularly delicate fish filleting in the near future. More likely the occasional bit of fish, some poultry (inc. bones), and ideally veg...

Would it be possible to put a bit of a proper grind on the underside which would stop it steering, and make it a more general-purpose knife? Anyone tried similar?


----------



## Kippington

You could try it, but it would be like a bastard child of the two disciplines. I don't think you'll ever successfully get rid of the steer completely, that would take an insane amount of steel removal from a deba. It would weigh something like 70% of it's original weight, and would be significantly shorter at the heel.


----------



## Nemo

cotedupy said:


> A quick q.- I have a cheap Deba, which to be honest I'm unlikely to use for any particularly delicate fish filleting in the near future. More likely the occasional bit of fish, some poultry (inc. bones), and ideally veg...
> 
> Would it be possible to put a bit of a proper grind on the underside which would stop it steering, and make it a more general-purpose knife? Anyone tried similar?


Much easier to buy a heavyweight gyuto or a "western deba"


----------



## Kippington

Oh and I was assuming it was a honyaki/monosteel deba. Wouldn't work at all if it's laminated.


----------



## cotedupy

Thank you guys, you have saved me a lot of fruitless effort! It shall remain a nice-looking, but largely unused, knife. Not something I have any problem with at all tbh... and feck it maybe I'll take up fishing, I am living on a beach atm


----------



## ian

Kippington said:


> Oh and I was assuming it was a honyaki/monosteel deba. Wouldn't work at all if it's laminated.



Sorry, why would it be harder if it was laminated? They’re ni mai, not san mai, correct? I can see the concavity on the left side making it hard to ever turn it into a gyuto, though.


----------



## Nemo

ian said:


> Sorry, why would it be harder if it was laminated? They’re ni mai, not san mai, correct? I can see the concavity on the left side making it hard to ever turn it into a gyuto, though.


I think that there are two potential problems:

1) the new cutting edge would be pretty close to (maybe within) the soft cladding.

2) there is a lot of hardened steel to grind through to get it there (although this would be the same with a monosteel).


----------



## ian

Nemo said:


> 1) the new cutting edge would be pretty close to (maybe within) the soft cladding.



I’m assuming you’d mostly just grind on the right (clad) side, since it’s ni mai.




Nemo said:


> 2) there is a lot of hardened steel to grind through to get it there (although this would be the same with a monosteel).



and then a fair amount of the metal would be cladding.


----------



## Kippington

ian said:


> Sorry, why would it be harder if it was laminated? They’re ni mai, not san mai, correct? I can see the concavity on the left side making it hard to ever turn it into a gyuto, though.


I was refering to Nemo's first point. By trying to turn the ura into a convex surface to stop steering, you'd probably cause the edge to wander off the hardened steel and onto the ni-mai cladding.


----------



## ian

Makes sense. I guess I was imagining making it thinner and only minimally flattening/convexity the left side. Thanks to you both!


----------



## Kippington

ian said:


> Makes sense. I guess I was imagining making it thinner and only minimally flattening/convexity the left side. Thanks to you both!


Made an image for clarity.




Edge is now on the cladding.


----------



## GBT-Splint

Thanks OP, very clear explanations. 
I have a Honesuki that I bought years ago, used to be a 70/30, turned it into a single bevel knife, doing so taught me a lot about knife geometry. works great


----------



## DavidPF

Kippington said:


> *A Basic Explanation of Asymmetry*
> 
> Way back when I began sharpening I remember reading through many forum threads about asymmetry in double bevel knives and having no idea what was going on. All this talk about 70/30 and 80/20, "You should be doing this and shouldn't do that", but no real explanation for what was actually going on. So I ignored the whole thing and went on sharpening in my 50/50 way.
> 
> A few years (and many knives) later, I realized after spending hours grinding further back behind the edge, I had developed my understanding on kitchen knives to the point where I could not only understand, but explain it in simple-enough terms. It really boils down to 3 general rules which, when understood individually, combine to explain the whole thing.
> 
> So we'll start off with a diagram of a crappy knife, then introduce one rule at a time and improve it till we get something which represents a good knife (the rules are in random order and only numbered for ease of reading).
> 
> 
> 
> 
> 
> 
> _Figure 1. A huge, fat, symmetrical knife_
> 
> *Rule 1 - Food releases off a curved surface better than it does off a flat surface*
> 
> Most cuts we do in the kitchen are flat, and when a flat surface on the food comes into contact with a flat surface on the side of your knife, the large amount of surface area in contact between them increases drag and can be enough to hold them together. This is known as _stickage_, and it's a pain in the ass to put up with. We can minimize this nasty effect with the use of a curve instead of a flat on the side of the knife, because there is less surface area shared between a flat and a curve (the same effect can be had with a multi-faceted compound bevel) when compared to a flat-on-flat.
> 
> 
> 
> 
> _Figure 2. A curvy, fat, symmetrical knife_
> 
> *Rule 2 - The thinner the knife, the easier it moves through what it is cutting*
> 
> This is pretty much self explanatory. Thicker knives have to push more out of the way on either side as they pass through food.
> 
> But here's a problem: The thinner you make a knife, the less curve you can fit on either side. This compromises Rule 1, and so we have to balance how thin the knife is with how much stickage we are willing to put up with.
> The heat-treatment and kind of steel will determine how thin you can get your knife before its strength becomes compromised.
> 
> 
> 
> 
> _Figure 3. A curvy, thin, symmetrical knife_
> 
> So here we are at a nice compromise of thickness vs. curvature. Cut food falls off on either side of the knife and it's not so wide as to get wedged in the food all too often. Perfect, right?
> It turns out there's another way to improve the shape even further, and it has to do with how we use kitchen knives.
> When cutting food, we generally hold the knife in our dominant hand and the foodstuff in the other. Lets say you're right handed and the food is held securely in your left. Do you really need the ability for food to drop off the left side of your knife if you're already holding it down? We may as well sacrifice some of the curve on that side and make the knife thinner overall. Like so:
> 
> 
> 
> 
> _Figure 4. A curvy, thin, asymmetrical knife_
> 
> This flatter surface on the left also has the added benefit of helping your left hand guide the up/down movement of the knife in a more predictable fashion.
> Of course, using this little trick introduces a new problem: Steer.
> 
> *Rule 3 - Asymmetry in the grind will determine the amount of steer the user experiences*
> 
> A blade pushing through foodstuff will turn if it's getting deflected more on one side compared to the other. This asymmetry we introduced in Figure 4 has increased the amount of deflection on the right side, and as such the blade will steer towards the left (of the user).
> 
> 
> 
> 
> _Figure 5. Different amounts of deflection on either side of the blade (green arrows) will cause the knife to steer off-center (red arrow)_
> 
> We can counter-act this somewhat by sharpening the knife in such a way to make it want to steer in the other direction.
> 
> 
> 
> 
> _Figure 6. Asymmetrical sharpening. Note the right bevel is both shorter and more acute to the blue line when compared to the left_
> 
> If we zoom into the sharpened area you can see that the size and the angles of the bevels are uneven. This is done on purpose for two reasons: It helps steer the knife to the right, which in turn cancels out the existing steer to the left. And it also helps keep the sharp point closer in line to the middle of the blade (the blue line), which is very important in the case of clad/san-mai knives.
> 
> 
> 
> 
> _Figure 7. The differing size and angle of the bevels introduce deflection in the opposite direction of Figure 5, helping to cancel out any steering overall_
> 
> So that's basically it!
> Hopefully it's not too hard to understand and helps alleviate the confusion that some people have on the topic.
> I should point out that while these general rules do apply to single bevel knives, the sharpening of them is done differently to what I've shown here. No correction is done to steering on a single bevel knife.
> Let me know if I've missed something.


I'm sure I'm just echoing others by now, but thank you very much for the clear explanation!


----------



## DavidPF

soigne_west said:


> The thing I don’t get is the mark up for left handed grinds.


It may partly depend on human efficiency. When you're doing repetitive tasks involving manual dexterity, you get into a groove and you get faster and better at it. When someone says "Please create a backwards version of the same result", you slow down and lose your groove, and you don't have all the same muscle memory to count on. I have no idea how much of an influence on making left-handed knives this actually is. A custom-made knife is less likely to need a surcharge, because it was already custom anyway. But a matching left-handed version of something that's "semi-production" seems like it might really be more work. For knives that are 100% machine-produced, I don't know about factory tooling etc.


----------



## Kippington

DavidPF said:


> It may partly depend on human efficiency. When you're doing repetitive tasks involving manual dexterity, you get into a groove and you get faster and better at it. When someone says "Please create a backwards version of the same result", you slow down and lose your groove, and you don't have all the same muscle memory to count on. I have no idea how much of an influence on making left-handed knives this actually is. A custom-made knife is less likely to need a surcharge, because it was already custom anyway. But a matching left-handed version of something that's "semi-production" seems like it might really be more work. For knives that are 100% machine-produced, I don't know about factory tooling etc.


Sounds right to me! Well written btw, I had similar thoughts but never could put them into words.


----------



## Jeff

Kippington said:


> *A Basic Explanation of Asymmetry*
> 
> Way back when I began sharpening I remember reading through many forum threads about asymmetry in double bevel knives and having no idea what was going on. All this talk about 70/30 and 80/20, "You should be doing this and shouldn't do that", but no real explanation for what was actually going on. So I ignored the whole thing and went on sharpening in my 50/50 way.
> 
> A few years (and many knives) later, I realized after spending hours grinding further back behind the edge, I had developed my understanding on kitchen knives to the point where I could not only understand, but explain it in simple-enough terms. It really boils down to 3 general rules which, when understood individually, combine to explain the whole thing.
> 
> So we'll start off with a diagram of a crappy knife, then introduce one rule at a time and improve it till we get something which represents a good knife (the rules are in random order and only numbered for ease of reading).
> 
> 
> 
> 
> 
> _Figure 1. A huge, fat, symmetrical knife_
> 
> *Rule 1 - Food releases off a curved surface better than it does off a flat surface*
> 
> Most cuts we do in the kitchen are flat, and when a flat surface on the food comes into contact with a flat surface on the side of your knife, the large amount of surface area in contact between them increases drag and can be enough to hold them together. This is known as _stickage_, and it's a pain in the ass to put up with. We can minimize this nasty effect with the use of a curve instead of a flat on the side of the knife, because there is less surface area shared between a flat and a curve (the same effect can be had with a multi-faceted compound bevel) when compared to a flat-on-flat.
> 
> 
> 
> 
> _Figure 2. A curvy, fat, symmetrical knife_
> 
> *Rule 2 - The thinner the knife, the easier it moves through what it is cutting*
> 
> This is pretty much self explanatory. Thicker knives have to push more out of the way on either side as they pass through food.
> 
> But here's a problem: The thinner you make a knife, the less curve you can fit on either side. This compromises Rule 1, and so we have to balance how thin the knife is with how much stickage we are willing to put up with.
> The heat-treatment and kind of steel will determine how thin you can get your knife before its strength becomes compromised.
> 
> 
> 
> 
> _Figure 3. A curvy, thin, symmetrical knife_
> 
> So here we are at a nice compromise of thickness vs. curvature. Cut food falls off on either side of the knife and it's not so wide as to get wedged in the food all too often. Perfect, right?
> It turns out there's another way to improve the shape even further, and it has to do with how we use kitchen knives.
> When cutting food, we generally hold the knife in our dominant hand and the foodstuff in the other. Lets say you're right handed and the food is held securely in your left. Do you really need the ability for food to drop off the left side of your knife if you're already holding it down? We may as well sacrifice some of the curve on that side and make the knife thinner overall. Like so:
> 
> 
> 
> 
> _Figure 4. A curvy, thin, asymmetrical knife_
> 
> This flatter surface on the left also has the added benefit of helping your left hand guide the up/down movement of the knife in a more predictable fashion.
> Of course, using this little trick introduces a new problem: Steer.
> 
> *Rule 3 - Asymmetry in the grind will determine the amount of steer the user experiences*
> 
> A blade pushing through foodstuff will turn if it's getting deflected more on one side compared to the other. This asymmetry we introduced in Figure 4 has increased the amount of deflection on the right side, and as such the blade will steer towards the left (of the user).
> 
> 
> 
> 
> _Figure 5. Different amounts of deflection on either side of the blade (green arrows) will cause the knife to steer off-center (red arrow)_
> 
> We can counter-act this somewhat by sharpening the knife in such a way to make it want to steer in the other direction.
> 
> 
> 
> 
> _Figure 6. Asymmetrical sharpening. Note the right bevel is both shorter and more acute to the blue line when compared to the left_
> 
> If we zoom into the sharpened area you can see that the size and the angles of the bevels are uneven. This is done on purpose for two reasons: It helps steer the knife to the right, which in turn cancels out the existing steer to the left. And it also helps keep the sharp point closer in line to the middle of the blade (the blue line), which is very important in the case of clad/san-mai knives.
> 
> 
> 
> 
> _Figure 7. The differing size and angle of the bevels introduce deflection in the opposite direction of Figure 5, helping to cancel out any steering overall_
> 
> So that's basically it!
> Hopefully it's not too hard to understand and helps alleviate the confusion that some people have on the topic.
> I should point out that while these general rules do apply to single bevel knives, the sharpening of them is done differently to what I've shown here. No correction is done to steering on a single bevel knife.
> Let me know if I've missed something.




AMAZING EXPLANATION !!!


----------



## Fuzzy

Kippington said:


> *A Basic Explanation of Asymmetry*
> 
> Way back when I began sharpening I remember reading through many forum threads about asymmetry in double bevel knives and having no idea what was going on. All this talk about 70/30 and 80/20, "You should be doing this and shouldn't do that", but no real explanation for what was actually going on. So I ignored the whole thing and went on sharpening in my 50/50 way.
> 
> A few years (and many knives) later, I realized after spending hours grinding further back behind the edge, I had developed my understanding on kitchen knives to the point where I could not only understand, but explain it in simple-enough terms. It really boils down to 3 general rules which, when understood individually, combine to explain the whole thing.
> 
> So we'll start off with a diagram of a crappy knife, then introduce one rule at a time and improve it till we get something which represents a good knife (the rules are in random order and only numbered for ease of reading).
> 
> 
> 
> 
> 
> _Figure 1. A huge, fat, symmetrical knife_
> 
> *Rule 1 - Food releases off a curved surface better than it does off a flat surface*
> 
> Most cuts we do in the kitchen are flat, and when a flat surface on the food comes into contact with a flat surface on the side of your knife, the large amount of surface area in contact between them increases drag and can be enough to hold them together. This is known as _stickage_, and it's a pain in the ass to put up with. We can minimize this nasty effect with the use of a curve instead of a flat on the side of the knife, because there is less surface area shared between a flat and a curve (the same effect can be had with a multi-faceted compound bevel) when compared to a flat-on-flat.
> 
> 
> 
> 
> _Figure 2. A curvy, fat, symmetrical knife_
> 
> *Rule 2 - The thinner the knife, the easier it moves through what it is cutting*
> 
> This is pretty much self explanatory. Thicker knives have to push more out of the way on either side as they pass through food.
> 
> But here's a problem: The thinner you make a knife, the less curve you can fit on either side. This compromises Rule 1, and so we have to balance how thin the knife is with how much stickage we are willing to put up with.
> The heat-treatment and kind of steel will determine how thin you can get your knife before its strength becomes compromised.
> 
> 
> 
> 
> _Figure 3. A curvy, thin, symmetrical knife_
> 
> So here we are at a nice compromise of thickness vs. curvature. Cut food falls off on either side of the knife and it's not so wide as to get wedged in the food all too often. Perfect, right?
> It turns out there's another way to improve the shape even further, and it has to do with how we use kitchen knives.
> When cutting food, we generally hold the knife in our dominant hand and the foodstuff in the other. Lets say you're right handed and the food is held securely in your left. Do you really need the ability for food to drop off the left side of your knife if you're already holding it down? We may as well sacrifice some of the curve on that side and make the knife thinner overall. Like so:
> 
> 
> 
> 
> _Figure 4. A curvy, thin, asymmetrical knife_
> 
> This flatter surface on the left also has the added benefit of helping your left hand guide the up/down movement of the knife in a more predictable fashion.
> Of course, using this little trick introduces a new problem: Steer.
> 
> *Rule 3 - Asymmetry in the grind will determine the amount of steer the user experiences*
> 
> A blade pushing through foodstuff will turn if it's getting deflected more on one side compared to the other. This asymmetry we introduced in Figure 4 has increased the amount of deflection on the right side, and as such the blade will steer towards the left (of the user).
> 
> 
> 
> 
> _Figure 5. Different amounts of deflection on either side of the blade (green arrows) will cause the knife to steer off-center (red arrow)_
> 
> We can counter-act this somewhat by sharpening the knife in such a way to make it want to steer in the other direction.
> 
> 
> 
> 
> _Figure 6. Asymmetrical sharpening. Note the right bevel is both shorter and more acute to the blue line when compared to the left_
> 
> If we zoom into the sharpened area you can see that the size and the angles of the bevels are uneven. This is done on purpose for two reasons: It helps steer the knife to the right, which in turn cancels out the existing steer to the left. And it also helps keep the sharp point closer in line to the middle of the blade (the blue line), which is very important in the case of clad/san-mai knives.
> 
> 
> 
> 
> _Figure 7. The differing size and angle of the bevels introduce deflection in the opposite direction of Figure 5, helping to cancel out any steering overall_
> 
> So that's basically it!
> Hopefully it's not too hard to understand and helps alleviate the confusion that some people have on the topic.
> I should point out that while these general rules do apply to single bevel knives, the sharpening of them is done differently to what I've shown here. No correction is done to steering on a single bevel knife.
> Let me know if I've missed something.


Thank you, very helpful. Had the idea now have the pictures. Thumbs UP


----------

