Change from 70/30 to 50/50 edge

[HappyamateurDK]

Hey all.

I recently bought a Kiya no. 6 carbon gyuto. I can't say for sure, but I have a strong suspicion it's a rebranded Misono Swedish carbon.

Would there be any disadvantages getting it resharpened to a 50/50 edge instead of the factory 70/30 edge?

It would make it easier for me to maintain a 50/50 edge.

Have a nice day

 

[ModRQC]

You can sharpen it at whatever angle you like. Won't change the fact that the grind is flatter on the left side, thus asymmetric. Since it's monosteel you don't have to worry about the edge passing from core to cladding. Eventually, your symmetrical sharpening would tend to make the grind more and more symmetric too.

 

[HappyamateurDK]

You can sharpen it at whatever angle you like. Won't change the fact that the grind is flatter on the left side, thus asymmetric. Since it's monosteel you don't have to worry about the edge passing from core to cladding. Eventually, your symmetrical sharpening would tend to make the grind more and more symmetric too.

But will an 50/50 edge on a asymmetric grinded knife make it perform worse ?

 

[Benuser]

Eventually, your symmetrical sharpening would tend to make the grind more and more symmetric too.

I'd tend to respectfully disagree. The edge of the asymmetric knife is off-centered to the left. If you keep it in place, but sharpen it only at the same angle, expect strong clock-wise steering, especially after a few sharpenings. As the right bevel will no longer form a continuous arc with the right face, I expect a serious loss of performance.
In no way the way you sharpen the edge can modify the fundamentals of the blade.
You may regrind the left face and add some convexity to it, and in the same time recenter the edge as well. Quite an operation and a waste of material which will shorten the blade's life span, but it is possible. Expect a poorer food release.
If you create even bevels on both sides, thus recentering the edge, without regrinding the left face, a sharp shoulder will raise on the left face, causing anti-clockwise steering. That's what eventually happens if you go on sharpening both sides equally as some salesmen suggest.

A Basic Explanation of Asymmetry

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...

www.kitchenknifeforums.com

Asymmetry The REAL DEAL

When we venture into using Japanese kitchen knives we often find that we’re interested in sharpening our own knives and begin searching for information on this subject. This leads us to research waterstones, sharpening techniques, and the subject of blade asymmetry inevitably comes up...

www.kitchenknifeforums.com

 

[ian]

But will an 50/50 edge on a asymmetric grinded knife make it perform worse ?

Yea, steering is the issue.

 

[Benuser]

Have seen quite a few Japanese knives that had undergone such a treatment with an Edge Pro. Both sides equally sharpened, both in angle as in amount. Very nice edges, by the way. Horrific performers, far to thick behind the edge, steering and wedging like crazy.
Quite a job to have it again work properly. Not very difficult, but time consuming, and a big waste of steel. The best time one has with a knife was gone.

 

[slickmamba]

if the asymmetry is just at the edge, yes you can totally regrind to 50/50 and never think about it again

 

[ModRQC]

Misonos ain’t got much beef to pretend at asymmetry. Sharpening symmetrically won’t change much, push the edge slowly back to center, and on a long enough timeline of multiple sharpenings, it will just look like any J-knife that are pretending to be symmetrical but are mostly offset favoring the right side.

Now if we were talking Masahiro VC I wouldn’t have risked my initial answer here.

 

[esoo]

My lefty Misono was clearly asymmetric all the way down from the spine. You were never getting it to be a true 50/50

 

[Ruso]

What other’s said - if the knife is 30/70 making it 50/50 will result in steering.
Same goes if you try converting 50/50 into 30/70 or what not.

 

[ModRQC]

Misono Dragon just came in:

This knife could either be sooo easily brought symmetrical, soooo easily worked on to accentuate this to something 95/5 that would actually mean something with a needle like blade of this type.

Now Masahiro VC on the other hand:

while doable would be a lot of work and losing actual significance of the intended grind.

In a Misono gyuto case I think asymmetrical is mostly romanticism.

 

[ian]

if the asymmetry is just at the edge, yes you can totally regrind to 50/50 and never think about it again

If the asymmetry is just at the edge, whoever sharpened the knife should be spanked.

 

[ModRQC]

Converting an asymmetrical knife in a needle-like geometry is easy, and especially easy on any knife not brought up thin behind the edge OOTB, thus about 1/2 to 1/3 as thick anywhere within 5mm closing to the edge as at the spine, making any asymmetry even more easier to blend with much needed thinning into symmetry. Needle like geometries are easy because they're mostly too thin throughout to be treated any much different than any other V grind, or to see asymmetry really change something in cutting if the edge is treated symmetrically.

One exception was my Morihei Hisamoto, which was ridiculously thin throughout while not particularly behind the edge, and ridiculously sharpened pretty much like a single-bevel - with an "almost-" ura left side. I made it, and sharpened it, into a symmetrical grind. It steered some OOTB, but mostly was too flexible because too thin, which aggravated what little steering there really was. Two sessions sufficed to erase steering and make it very very keen but ordinary, with a 50/50 edge.

If you want to see that a knife has been brought asymmetrical throughout in a significant way, look at the choil but only in conjunction with the tip as seen in a perfectly straight spine shot: tip should be mostly flattened on the non cutting side, tapering only on the cutting side. Misono knives ain't nothing like that, the tip is about symmetrically tapered on both sides. Edge is sharpened 70/30, and knife grinded 70/30 just over it with that well known overpolished shoulder. There is some added convexity to the cutting side, some flatness on the non-cutting side, but mostly a V grind with exaggerated asymmetry at the edge only. It's essentially ready to be treated asymmetrically, but with thin grinds not thin behind the edge, it's also pretty much ready to be treated symmetrically. Just sharpening 50/50 a couple of times would already see most of the exaggeration at and just behind the edge blending into a mostly-V edge that the asymmetrical grind throughout the faces is already tending to blend into anyway.

Rest is just romanticizing over the idea of asymmetry. Bring me beef in geometry, grinded almost flat on the non-cutting side, and already thin behind the edge, and that will be where you really need to start working with asymmetry. In cheaper knives, only Masahiro VC pretended as much, even though the Morihei Hisamoto really tried too.

 

[DavidPF]

Do Japanese cooks in Japan run into all these problems? If not, why not? If they do, why don't the knife makers bother learning to fix the problem?

It's not "just a Japan thing"... Toyotas and Hondas don't ship with asymmetric gearing that runs the right side of the car 30% faster than the left side, and expect every customer to know how to shim the steering to compensate.

 

[Kawa]

Do Japanese cooks in Japan run into all these problems? If not, why not? If they do, why don't the knife makers bother learning to fix the problem?

It's not "just a Japan thing"... Toyotas and Hondas don't ship with asymmetric gearing that runs the right side of the car 30% faster than the left side, and expect every customer to know how to shim the steering to compensate.

Well, steering isn't a problem if you learn how to use it, account for it and get used to it. And with time, you don't know better.
I have a Sakai Takayuki gyuto with a 70/30 edge OOTB, and I maintained it that way. As a starter I might changed it unintentially to 80/20 or 65/35 (or whatever) after sharpening. Immediately I could feel difference in steering, but that only lasts for a week. After that you can switch knives during a prep and there is no problem with steering, because you will know how your knives handle and you automatically correct.

You only notice it with a new knife or if the edge has been changed after sharpening. After a (short) while, you work with your tool.


This is all amateur homecook opinion, dont know how it will feel after 8 hours of cutting...


Whats the intended reason for a 70/30 edge for example? It that a middle way between a 50/50 grind and a singel bevel? More precision, but not the max steering?

 

[Benuser]

Look at a vintage Sab, or a German knife from the twenties. You will notice a right face that's convexed on its entire width, and a left one that has a curve only in the last one or two centimetres.
The round right face helps with food release.
The makers didn't want to have both face an identical curvature, which would cause easy wedging. Just as with axes.
The only thing Japanese makers did was further improving the food release by off-centering the edge to the left, and so reducing the curvature on the left face.

 

[DavidPF]

Look at a vintage Sab, or a German knife from the twenties. You will notice a right face that's convexed on its entire width, and a left one that has a curve only in the last one or two centimetres.
The round right face helps with food release.
The makers didn't want to have both face an identical curvature, which would cause easy wedging. Just as with axes.
The only thing Japanese makers did was further improving the food release by off-centering the edge to the left, and so reducing the curvature on the left face.

I'm happy learning from this entire group of people in general, but Ben, in my experience your answers to people's questions (my own but many others' too) are particularly useful. Thank you.

Sure, it's partly because you know about blades, but it's also because you tend to answer with a real understanding of what the question meant. Not everyone has that.

 

[Nemo]

Do Japanese cooks in Japan run into all these problems? If not, why not? If they do, why don't the knife makers bother learning to fix the problem?

It's not "just a Japan thing"... Toyotas and Hondas don't ship with asymmetric gearing that runs the right side of the car 30% faster than the left side, and expect every customer to know how to shim the steering to compensate.

Have a read of Kip's thread (referenced/ linked above), "A basic explanation of assymetry".

Hopefully it will become clear why assymetry is not a problem that needs to be fixed, but a deliberate strategy to try to optimise the tradeoff between thinness and food release. Tends to work pretty well, too.

 

[DavidPF]

Have a read of Kip's thread (referenced/ linked above), "A basic explanation of assymetry".

I had already read it, and then read what was here, and was getting confused. Note to those with considerable experience: the truth about how knives work can sound really stupid to someone who never had to think about it before.

 

[DavidPF]

... assymetry is not a problem that needs to be fixed, but a deliberate strategy to try to optimise the tradeoff between thinness and food release. Tends to work pretty well, too.

Not as well as people tend to wish it would, considering the fairly frequent discussions of food release issues. Or are those discussions generally happening among people whose knives don't have this feature (i.e. are either more primitively ground or are too thin to have a shape)?

("Too thin to have a shape" is something I tend not to appreciate in other parts of life as well.)

Thinking about it a little more, food diameter would have to come into this too; maybe one reason why garlic seems to be a lost cause for sticking, other than it literally is sticky stuff.

 

[McMan]

Not as well as people tend to wish it would, considering the fairly frequent discussions of food release issues. Or are those discussions generally happening among people whose knives don't have this feature (i.e. are either more primitively ground or are too thin to have a shape)?

("Too thin to have a shape" is something I tend not to appreciate in other parts of life as well.)

Thinking about it a little more, food diameter would have to come into this too; maybe one reason why garlic seems to be a lost cause for sticking, other than it literally is sticky stuff.

Required Reading:

A Basic Explanation of Asymmetry

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...

www.kitchenknifeforums.com

 

[Nemo]

Not as well as people tend to wish it would, considering the fairly frequent discussions of food release issues. Or are those discussions generally happening among people whose knives don't have this feature (i.e. are either more primitively ground or are too thin to have a shape)?

("Too thin to have a shape" is something I tend not to appreciate in other parts of life as well.)

Thinking about it a little more, food diameter would have to come into this too; maybe one reason why garlic seems to be a lost cause for sticking, other than it literally is sticky stuff.

Well, of course it is a continuum.

However, to say that it doesn't work because people still talk about food release and how to improve it is like saying that a Formula 1 car doesn't handle well because people still talk about how to make them handle even better.

Yes, food size and composition has an effect on food seperation. In my car analagy, I guess that this is lile saying that the road is grippy or slippery.

 

[DavidPF]

However, to say that it doesn't work because people still talk about food release and how to improve it is like saying that a Formula 1 car doesn't handle well because people still talk about how to make them handle even better.

F1 drivers aren't saying "I keep having to get out of the car and steer the wheels by hand"

I think a lot of cooks get no better food release with their good knives, or only marginally better, than they would with a $3 knife. I'd be grateful to be wrong, and find out that all decent knives are very noticeably better at release than the proverbial Walmart special.

 

[Nemo]

F1 drivers aren't saying "I keep having to get out of the car and steer the wheels by hand"

I think a lot of cooks get no better food release with their good knives, or only marginally better, than they would with a $3 knife. I'd be grateful to be wrong, and find out that all decent knives are very noticeably better at release than the proverbial Walmart special.

You can, of course, make any analogy break by changing the point that is being made. You have domonstrated this well.

Having said that (as previously explained), when appropriately sharpened, double bevelled assymetric knives by and large do not steer. In my (limited) experience, single bevel knives are an altogether different kettle of fish.

A number of people have made a pretty decent attempt to explain the phenomenon of assymetry to you but you have argued almost every point while at the same time using your inexperience as a reason for not understanding.

If you don't want an assymetric knife, that's OK. If you want a $3 knife, that's OK too. Not the sort of stuff we usually talk about here, but it's OK.

I don't think that it's reasonable to argue, on the basis of (by your own admission) limited experience, that assymetric knives do not confer any benefit in use, in the context of many experinced knife users, sharpeners and knifemakers who are telling you that they actually do.

 

[McMan]

F1 drivers aren't saying "I keep having to get out of the car and steer the wheels by hand"

I think a lot of cooks get no better food release with their good knives, or only marginally better, than they would with a $3 knife. I'd be grateful to be wrong, and find out that all decent knives are very noticeably better at release than the proverbial Walmart special.

Then buy a bunch of these $3 knives. Happy trails!

 

[Kawa]

@Nemo , I understand your answer.
After reading this whole topic back with my morning coffee, I noticed that 2 things seem to mixed up here:

First we were mainly talking assymetry (the why, what does it do etc) at the blades face and/or cutting edge.
Suddenly the subject was changed to food release.

I see these subjects are strangled together, but can also be debated as 2 various subjects.


If that is true, I can understand were the question come from:
- Steering wil get 100% solved when an assymetric shape or edge has the perfect balance. A balanced knife simply doesnt steer.
- A perfectly balanced (assymetric grind with no steering) knife still can have bad food release.
- No knife has perfect food release for all ingredients.

@DavidPF
I think food release is better with an overthought knife. How much better? I can't tell. Maybe this is the kind of thing you notice and start appreciating after 8 hours of cutting every day (aka home amateur cook versus professional).

I've seen videos of someone cutting potatoes, which did stick a lot.
He changed something to his knife (can't remember what) and the next shot those same potatoes stopped sticking for 100%.

 

[Benuser]

I've seen videos of someone cutting potatoes, which did stick a lot.
He changed something to his knife (can't remember what) and the next shot those same potatoes stopped sticking for 100%.

Supposing they were the same type of potatoes, same temperature, and so on, same technique, only reflecting on the knife, I guess he off-centered the edge to the left, and let the right bevel continue the right face's convexity. No shoulder, one continuous arc. That's how I do with Sabs and vintage Germans or Sheffields.

 

[Kawa]

A lot of possible variables, yes

 

[DavidPF]

Then buy a bunch of these $3 knives. Happy trails!

Several experienced people have given slightly waffle-y responses, not confident at all that their knives release food THAT much better than anything else. So it's a breath of fresh air to find someone who's so confident he doesn't even bother to think or try to answer. Show your personal video with potatoes, garlic, and cheese falling right off your knife; or think for just a moment about the situation. Thinking might do you good, you never know until you try.

 

[jwthaparc]

What a fun thread!