A Basic Explanation of Asymmetry

[Benuser]

U

Thanks. Will try.

What kind of knife is concerned?

 

[Bolek]

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.

 

[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!

 

[HRC_64]

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?

 

[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.

 

[tripleq]

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.

 

[woodworkcan]

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.

 

[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?

 

[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.

 

[Kippington]

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.

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.

 

[TEWNCfarms]

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.

 

[zetieum]

moderators: stick this post!

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

 

[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?

 

[TEWNCfarms]

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...

 

[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.

 

[TEWNCfarms]

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!

 

[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.

 

[Kippington]

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

Cool way of phrasing it! :doublethumbsup:

 

[TEWNCfarms]

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

 

[Benuser]

My pleasure.

 

[TEWNCfarms]

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

 

[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.

 

[TEWNCfarms]

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

 

[Benuser]

You're most welcome.

 

[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!

...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 'shallow' 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.

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.