A 30/70 right hand 70/30 left hand edge bevel.

[Transmaster]

I have 3 knives that are ground 30/70 except for the fact I could get them ground this way I am not sure why I purchased them with such a grind now. I was worried at first how I would maintain the edge geometry. There are several YouTube showing professional sharpenders doing it by hand with whetstones more or less Like what I have in My collection. It is no big deal. Now that I know what to look for I don't see any of these professionals using anything more than perhaps a #2000 grit stone to finish with. Having such a edge grind is one of those things that only a exacting professional chef can make use of, or need. For the rest of us we probably couldn't tell the difference.

 

[Desert Rat]

https://www.kitchenknifeforums.com/threads/a-basic-explanation-of-asymmetry.33951/

 

[Kawa]

Are we talking about 1 side has an obtuse angle and the other side has a shallow angle?

Or do both sides have the same bevel angle, but the 2nd bevel is thicker/heigher on one side and smaller on the other?

Both will be called 30/70 (or 40/60 whatever) sometimes. Or even assymetric grind.

 

[Transmaster]

https://www.kitchenknifeforums.com/threads/a-basic-explanation-of-asymmetry.33951/

Thanks a good explanation.

I have been looking at this issue and it is beyond anything that would apply to me. It would be interesting to have someone who actually has use for these alternative grinds and how they would be used educate us.

 

[Kawa]

Im still not sure what youve got.

Your picture is exaclty what I mean above, but has a better description then I call it: do you have different angles of edge offset?

You just cut with them like any other knife. They probably feel like they are steering, but you get used to that.

 

[azn_knives_4l]

Im still not sure what youve got.

Your picture is exaclty what I mean above, but has a better description then I call it: do you have different angles of edge offset?

You just cut with them like any other knife. They probably feel like they are steering, but you get used to that.

I read at one point that all knives steer and that we adjust. I think it was Shihan.

 

[Transmaster]

Until I get a microscope for viewing knife edges I will not know what kind of 30/70 grind I have on the what I have.

Of I all of the knives I have I consider this Messermeister Kakugata Usuba to be one of my very best. I had to order it from Australia.

 

[Delat]

That looks more like a single bevel than what’s commonly referred to as asymmetric grind. Single bevels are their own sort of peculiar beast with their own specific sharpening requirements.

 

[kujaku]

my Deba(single bevel)

 

[kujaku]

the sukehisa instruction manual, which explains the angle at which to sharpen the knives and how to sharpen them.
from the description of the sharpening method, it seems natural to interpret the 7:3 as a ratio of time or frequency of sharpening.

 

[Benuser]

The 70/30 gives an idea of how much the edge is off-centered — to the left, in the case of a right bias.

 

[ile74]

Until I get a microscope for viewing knife edges I will not know what kind of 30/70 grind I have on the what I have.

Of I all of the knives I have I consider this Messermeister Kakugata Usuba to be one of my very best. I had to order it from Australia.

View attachment 329697

View attachment 329696

View attachment 329698

Single bevel knives have 0/100 asymetric angles and 0/100 offset. They have thin edges but tend to steer in hard foods. Steering is desired in certain techniques for shaving thin slices like katsuramuki. Asymmetric sharpening aims at the good sides of both world, a thin blade and prevention of steering.

I myself sharpen a lot of single bevel knives and it is a natural way of sharpening for me. The knife is in the dominant hand and most of the sharpening is done with edge trailing strokes. The burr is removed by turning the knife and sharpening with edge leading strokes. So my double bevel knives also tend to be naturally something like 30/70, 20/80 and offset too.

Sharpen as you see comfortable. Adjust the angle and how much you sharpen on the right and left side depending on how much the knife steers.

 

[ile74]

from the description of the sharpening method, it seems natural to interpret the 7:3 as a ratio of time or frequency of sharpening.

This is exactly what I think about sharpening asymetrically. It can also be seen in the cross-section of the geometry.

 

[Delat]

the sukehisa instruction manual, which explains the angle at which to sharpen the knives and how to sharpen them.
from the description of the sharpening method, it seems natural to interpret the 7:3 as a ratio of time or frequency of sharpening.
View attachment 329854

https://knifewear.com/blogs/articles/single-bevel-sharpening

 

[Delat]

Here’s a more common example of asymmetry like @Benuser mentions. You can see the core steel offset to one side. Although both sides are convex, there’s more convexity on the right face (when edge down) to improve food release.

Sharpening and thinning should be done in a way to keep the core at the edge while respecting the geometry and reducing steering. I don’t have this knife anymore but I think I was sharpening at 10 degrees right, 20 left.

 

[azn_knives_4l]

The 70/30 gives an idea of how much the edge is off-centered — to the left, in the case of a right bias.

I really need to explore this more but it's scary I accidentally sharpened noticeable and negative steering into my Kochi at one point and followed Jon's advice to fix but I really want to test for myself if it's because surface area or centering of the apex or shape of the sides or what, lol. Jon describes as due to surface area, fwiw, and I trust him so I'll repeat that here but I still want to learn more. Reading on wedge physics would answer, too, but that's so boring.

 

[Transmaster]

That looks more like a single bevel than what’s commonly referred to as asymmetric grind. Single bevels are their own sort of peculiar beast with their own specific sharpening requirements.

Yes, this is the trademark grind of the Usuba, it also has the hollow ground back side, the urasuki. I asked the US HQ'ed Messermeister why they didn't sell this Usuba State side and they told me people were just interested in the Nakiri. That people looking for a Usuba knew exactly what they were and knew how to use them.

 

[ile74]

Although both sides are convex, there’s more convexity on the right face (when edge down) to improve food release.

So the left side is less convex, and therefore the secondary bevel must be steeper (higher angle) to counter steering. Did I understand right?

Edit: Just to clear my communications, I don't mean to argue but to learn things.

 

[azn_knives_4l]

So the left side is less convex, and therefore the secondary bevel must be steeper (higher angle) to counter steering. Did I understand right?

I don't think it's this. These need balanced against depth and angles, too, so it's more holistic.

 

[Transmaster]

My Usuba is Kimchi magic I use it on the cabbage and the Daikon radishes.

 

[ile74]

I don't think it's this. These need balanced against depth and angles, too, so it's more holistic.

The most extreme example of asymetric sharpening is single bevel with 0/100 angle and 0/100 offset. Only way to counter steering is to lift spine on uraoshi sharpening and basically do some over zero degree secondary bevel which is totally unacceptable.

 

[azn_knives_4l]

The most extreme example of asymetric sharpening is single bevel with 0/100 angle and 0/100 offset. Only way to counter steering is to lift spine on uraoshi sharpening and basically do some over zero degree secondary bevel which is totally unacceptable.

Right. But these can be balanced in numerous ways otherwise.

 

[ile74]

Right. But these can be balanced in numerous ways otherwise.

I don't mean to argue but to learn things. What do you think they are, additionally to offset and left/right side angles?

 

[azn_knives_4l]

I don't mean to argue but to learn things. What do you think they are, additionally to offset and left/right side angles?

It's some balance of these as they relate to shape/curvature, surface area, and even the finish. I think the physics are most similar to drag so all of it matters like with a boat's hull in water.

Edit: This segment of physics is *wild*. Fluid dynamics is hell and the first principles models are overwhelming to many, many people.

 

[kujaku]

https://knifewear.com/blogs/articles/single-bevel-sharpening

Sorry if this was confusing, but I was talking about double beveled knives.

 

[ile74]

It's some balance of these as they relate to shape/curvature, surface area, and even the finish. I think the physics are most similar to drag so all of it matters like with a boat's hull in water.

Ok, so we discussed a different matter. I was discussing bevel geometry. Not about the finishes of the surfaces.

 

[azn_knives_4l]

Ok, so we discussed a different matter. I was discussing bevel geometry. Not about the finishes of the surfaces.

You can't leave these out of the equation to steering. They absolutely matter.

 

[ile74]

You can't leave these out of the equation to steering. They absolutely matter.

Do you say that for example yanagiba, which is made kurouchi, tsuchime, kasumi, hon kasumi or honyaki steer differently if the geometry is exactly same?

 

[azn_knives_4l]

Do you say that for example yanagiba, which is made kurouchi, tsuchime, kasumi, hon kasumi or honyaki steer differently if the geometry is exactly same?

You're getting really deep into specifics on extreme corner cases. Are we talking generally or do you have a specific knife or construction in mind? Your example here is entirely different from your earlier questions and statements. Short answer? Maybe.

 

[Benuser]

Once you're used to a strongly asymmetric double-bevelled blade, you compensate for steering by very slightly turning your wrist clockwise. It will add friction to the left side, and reduce to the right one.