# Right handed 70/30 uneven grind bevel angles



## justmarc (Jan 13, 2018)

I recently purchased several relatively inexpensive kitchen knives, all are SS, (Vanadium SS, Vg-10, and AUS8). They are 120mm and 150mm Pettys and gyutos and one is a 210mm Wa Gyuto VG-10.
Any bevel angle suggestions for sharpening these 70/30 grind uneven bevel knives?


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## Grunt173 (Jan 13, 2018)

Until something else is suggested,maybe this will help.
[video=youtube;LEiAVk7x2JM]https://www.youtube.com/watch?v=LEiAVk7x2JM[/video]


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## JBroida (Jan 13, 2018)

excuse the copy and paste from an email i wrote a while back:

Sharpening angles are one of the most common things I am asked about. I find it's often important to talk about them together with asymmetry, but let me address the sharpening angles first. In general, there is not going to be an exact angle that is correct, but rather a range of angles that works. For instance, most double bevel Japanese knives will work well with angles somewhere between 10-15 degrees per side. The closer you are to the 10-degree side of things, the sharper the knife will feel, but it will also be more fragile, brittle, and may not hold its edge as long. The closer you are to the 15-degree side of things, the more tough and durable the knife will be, though it won't feel quite as sharp. It's also ok to go even lower or higher than this, depending on your personal preference, though I often recommend staying within this range until you have a better understanding of how things work for you. For what its worth, Japanese craftsmen aren't measuring the angles when they make or sharpen the knives either. Lastly, it's important to keep in mind that you don't have to always use the exact same angle. If you want your knife to feel a bit sharper, go a bit lower. If you need a more tough and durable edge, go a bit higher.

As for asymmetry, it seems that this is a rather confusing issue for many. Part of the confusion stems from the fact that many of the ways that we describe these asymmetries are gross oversimplifications. For example, the ratios like 50/50 or 60/40 don't really describe anything of substance. Is it the ratio of the percentage of sharpening on each side? Is it a ratio of the angles on each side? In reality, it's neither. No craftsman in Japan it's there and measures angles or ratios. What really matters is the way that the knife cuts. The asymmetry deals with two main issues-thinness behind the edge and steering. The more asymmetrical a knife is, assuming the angles are equal, the thinner the knife is behind the edge. However, the more asymmetrical the knife is, the more likely it is to steer. It's also important to keep in mind that the angles are not always equal. When figuring out asymmetry for any given knife, the first thing that you want to do is cut with the knife. When you cut with a knife, you want to assess whether it is steering to the right or to the left, and how easily it moves through the food. If you notice that your knife is steering to one direction or the other, you want to create more surface area on the side that it is steering towards, so that the knife cuts straight. This can be done by adjusting the angle (either more or less acute) and/or adjusting the amount of time spent sharpening on each side. If you notice that the knife is wedging in food as it goes through, this may mean that you need to sharpen at a more acute angle, or that you need to thin behind the edge. Some of this can also be dealt with through adjusting asymmetry, as previously mentioned. Does that make sense?


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## justmarc (Jan 13, 2018)

John, Thank you for your explanation. That's the first time anyone ever explained it in a real and practical sense of using the asymmetrical bevels.


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## Nemo (Jan 13, 2018)

As ever, Jon's explanation makes a confusing topic easy to understand.

It's also worth looking at Kippington's visual explanation of assymetry: http://www.kitchenknifeforums.com/showthread.php/33951-A-Basic-Explanation-of-Asymmetry


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## ian (Jan 14, 2018)

+1 to Kippington's thread and Jons reply.

There are a couple things I don't quite understand about asymmetric (say, single bevel, in the extreme) edges. If anyone has some input about how much of the following is on track, I'd love to hear it.

*****Why make/use them?*****

As far as I can see, there could be 4 reasons. For single bevel knives, they would be:

a) In some (for me, unusual) applications, like making sheets of cucumber using a rotating cut, the steering that comes with a single bevel can be useful. 

b) In a (right handed) single bevel knife, the edge bevel and globally convex geometry on the right side should push food away as you're cutting it, so it doesn't stick to the knife. You don't usually need the knife to push away the food on the left side, because you're holding it with your other hand, so it makes sense to concentrate this effect on the right by putting the bevel there.

c) It's (a little more than) half as much work to sharpen a single bevel knife.

d) People often say that single bevel knives are sharper, because of a smaller total edge angle. I'm a little confused about this, though, since then the question is "why don't we just sharpen double bevel edges with half the angle?". I'm guessing that there's something about the shape of the single bevel that makes a single bevel edge with 15/0 angles more durable than a double bevel with 7.5/7.5 angles? (I don't get why this would be true.) Additionally, I could imagine that it is easier to sharpen 15/0 than 7.5/7.5, because maybe it's harder to hold the small angle.... I'm just guessing blindly here though.

For double bevel asymmetric knives, c) isnt relevant, and lets forget about a) since I dont work in a Japanese restaurant. So, it seems like the main points would be b) and (maybe?) the ability to get smaller total angles because of some mysterious sort of increased durability in an asymmetric edge? 

*****How to sharpen asymmetric double bevel knives*****

Let's assume we don't want our knives to steer. I get that the point is to correct the steering effected by the overall geometry of the blade by sharpening the edge asymmetrically. (Although as Kippington explains, when you have a clad knife it's also important to line up the edge with the center of the blade so that the edge is just composed of the core steel.)

Presumably, the exact amount and direction that the knife steers is some complicated quantity depending on the overall geometry of the knife, the angles and lengths of the edge bevels, and maybe the position of the edge relative to the rest of the knife. 

You can understand how the edge position and the lengths of the edge bevels change under sharpening as follows. Essentially, these changes depend on the angles chosen for each side, and the time spent on each side.

For instance, here we have a (rather dull) 45/45 angle double bevel. After sharpening 3x as much on the right side, the edge moves to the left, and the right bevel gets longer than the left bevel.







Here we have 23/14 angle double bevel, and we sharpen the same amount on both sides. The edge moves slightly to the left, since the perpendicular to the 14 side points more to the left than the perpendicular to the 23 side points to the right, and the right bevel gets relatively longer. 






(Ok, in my picture the bevel on the right side also starts out slightly longer, so maybe itll actually take a bit longer to take metal off of that bevel, since the finger pressure is distributed over a larger area. Not sure how much this will matter, though, i.e. if it would cancel out the effects mentioned above.)

Presumably, if the overall geometry of the knife makes it want to steer to the left (as I guess is the case for right handed asymmetric knives), making the left edge bevel longer and a higher angle will compensate for that. As long as you can keep the edge basically in the center (should we make sure to do this for monosteel knives, or are there reasons not to?), you can basically balance the asymmetric angle ratio with the asymmetry in time spent on the two sides however you want, it doesnt matter too much which method of compensating for steering you emphasize more. Although I guess I can imagine that if you just decide Im just going to make the angles equal on both sides, and spend more time on the left side you could maybe get all the way to a (left-handed) single bevel edge without completely compensating for the steering.



Anyway, sorry for the neverending post. I realize that my goal to 

*completely figure out how the amount of steering is affected by the blade geometry, and to maximize how much my knife pushes away food to the right, while simultaneously compensating for steering and putting the edge right in the center*

will be completely impossible to implement using freehand sharpening (or any other kind, really), even if I somehow completely understand the geometry and composition of the knife Im using. So, of course, Ill mostly just try to compensate for steering by feel. It will definitely make me feel more comfortable with the whole thing if I have a good picture in my mind of what I am doing, and what I should be shooting for, rather than turning everything into trial and error.


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## Benuser (Jan 14, 2018)

Justa a few remarks: with a Japanese blade, you will often see the edge to be off-centered, to the left. This allows even a better food separation.
When you sharpen a knife you will first want to know whether you're OK with the previous configuration, in which case you may reproduce it on its new location. Start by thinning behind the edge, and raise the spine only little by little until you've raised a burr. Verify the scratch pattern to see the progress. Once the burr has been raised you may go to the other side, and start again, fairly behind the edge. No need of angle or proportion figures.
If you want to change anything: say you experience clock-wise steering. You may reduce the friction on the right side by some more thinning, you may end with a lower angle than before, or you may increase the angle at the left bevel.
Once you've eliminated steering, make sure to equally thin both sides, or you will disturb the balance.


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## ian (Jan 14, 2018)

Benuser said:


> Justa a few remarks: with a Japanese blade, you will often see the edge to be off-centered, to the left. This allows even a better food separation.



Is the expectation that the user will then just deal with the steering, by modifying cutting technique?


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## Benuser (Jan 14, 2018)

ianbiringer said:


> Is the expectation that the user will then just deal with the steering, by modifying cutting technique?



Yes, both cutting technique and sharpening will help.


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## toddnmd (Jan 14, 2018)

ianbiringer said:


> Is the expectation that the user will then just deal with the steering, by modifying cutting technique?



I don't think so. The last sentence refers to working toward eliminating steering.


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