asymmetric grind clarification

[TeaThyme]

Greetings

I was just reading a post that mentioned grinds not being symmetrical to help food release. I've never put any thought into this before. Can someone clarify whether the knife in this picture is meant for a left or right-handed person? How much does this actually effect the food release of the knife?

Would appreciate some enlightenment here

 

[Bico Doce]

The grind looks flatter on the left side (when the knife is in cutting position not in the picture) so it will favor right handed users. You want the side with more convexity facing opposite of what your cutting so it can aid in the release after the cut is made

 

[tostadas]

Asymmetric grinds usually have one side with more convexity, while the other side is flatter as Bico mentioned. However, it's often unclear just from a choil shot. Sometimes the choil is ground differently than the rest of the blade, or the blade itself is installed crooked, making it appear to be asymmetric.

One way to check is to look down the length of your knife, with one side facing up, and lay a credit card or other flat edge across it at different points. If you rock the credit card back and forth, you can get an idea of the convexity or flatness on that side. Repeat on the other, and compare the two.

 

[dragjp]

Supplementary video

credit to @milangravier
The whole recording helped me a lot to understand the profile and stone finishing, still review it couple times a week while learning jnats.

 

[Delat]

The info above is on the money. Here's an example that's pretty clear - it's often easier to tell with San Mai where the core is obvious.

In this choil shot you can see the core is clearly offset to the left blade face (right side in the photo). This gives the sharpener more "meat" or cladding on the right face to add convexity, while the left face is essentially flat.

 

[Benuser]

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

 

[TeaThyme]

Wow, thanks for the helpful information! This explains a lot

My first impression was that the right side of the blade (while cutting) is very flat. The left side is ground more at an angle but is completely straight, whereas the right side is very slightly convex.

 

[HumbleHomeCook]

Run a credit card or something along the sides and you'll see it. Cards are nice as they don't scratch.

 

[stringer]

I don't think anyone has really answered your question of how you would know if the geometry is inverted. Basically, you will experience steering (where the knife wants to veer one way or the other instead of kindly going straight down) especially in harder produce that is taller than the knife. You might also see stiction or general poor food release with wetter ingredients. And you would find it more difficult to do very thin slices. Inverted geometry will make fine detail work annoying. You can compensate for all of these things and make adjustments over time if you have a knife with bad geometry for your handedness or cutting style. But it's easier to start off with something that isn't working against you.

 

[Benuser]

In addition only to what @stringer said: strange steering has not always to do with geometry. In most cases it is just a burr that has been overlooked.

 

[esoo]

As a lefty, I can comment that the biggest issue you will see is poor food release from a knife that is right biased. Speaking in very general terms, many knives will be thin enough at and just behind the edge that they will still cut well, but as food travels up the blade it will tend to want to stick. This will be worse with large items (cucumber or mushroom slices) in that they will not want to wipe off the blade as easily.

Here is an example of fairly symmetric blade - a Myojin SG2. You can clearly see the core and that the amount of metal on each side of the core is fairly even

@Delat's example above shows a good example of asymmetric where the core is offset. Here is an example where the core is more centered, but you can see that the amount of metal on each side of the core is different. The core on right side (which is the left side when the blade is pointed down and in hand) is flatter. As I said, this knife will cut, likely without much steering, but there will be food release issues. This is a Hitohira Ashi.

The biggest issue that can be faced as a lefty is that you can see a choil online and it may look good, but these are hand made products that vary from knife to knife and you are likely not getting the knife they took a picture of. My most interesting case is I have a knife that was obviously meant for a right hander (due to the choil grind), but the rest of the blade is left biased.

 

[McMan]

I've found choil shots are not as helpful as they might seem when gauging asymmetry.
You could rotate the blade one or two degrees in either direction and it would still appear to be at 12 0'clock, but just these very minor adjustments one way or the other make the choil 'read' much more/less asymmetric than it might be.
It's easier to gauge using a choil shot if the blade is ground differently on each side--for example, is one side relatively flat and the food release side is more notably convexed.
For your blade, which appears flat ground, I'd suggest using a straight edge (like a business card). Sit the card flush on the big bevel. (If you can sit it flush, it's flat ground or concave; if you can't it's convex.) Whichever side has the card closer to the spine will (usually) answer your question about RH/LH.

 

[blokey]

I always find Glestain one of the best to demonstrate asymmetry, they makes both right and left hand knives, made very obivous by the side of dimples, and their convexity is very apparent.
https://miuraknives.com/japanese-kn...32-japanese-knife-glestain.html#/36-size-24cmhttps://miuraknives.com/japanese-kn...tk-japanese-knife-glestain.html#/49-size-19cm

 

[M1k3]

Choil shots can get you in the ballpark. Sometimes you might think you hit a home run. But you could actually just be sitting in the bleachers.

 

[esoo]

I always find Glestain one of the best to demonstrate asymmetry, they makes both right and left hand knives, made very obivous by the side of dimples, and their convexity is very apparent.
https://miuraknives.com/japanese-kn...32-japanese-knife-glestain.html#/36-size-24cmhttps://miuraknives.com/japanese-kn...tk-japanese-knife-glestain.html#/49-size-19cmView attachment 237064View attachment 237065

Misono Swedish has the same idea, with the change in side of the logos. Leftys don't get the dragon or flower engraving however.

 

[TeaThyme]

Ah, this is so interesting to see! The myojin choil seems killer!

Well I've been looking at a Yoshikage Kiritsuke 210 SKD specifically. I was so certain something was off with the knife. I had a suspicion it was a knife for a left-handed user. The choil picture I posted was of the knife in question. Unfortunately I can't really check anymore with a credit card. I only have the photos that I made. I will definitely pay more attention in the future to this. It's good to know some manufacturers make the bias clear with their logo.

 

[Benuser]

A little warning here, I repeat about ten times per year.
A lot of retailers present their knives as ambidextrous, even if they're are not. Have seen extremely right-biased blades blatantly being sold as ambidextrous. Apart from lasers truly ambidextrous Japanese knives are rare, very rare.
Another misunderstanding may raise from edges presented as 50/50, suggesting it makes a knife ambidextrous. It is perfectly possible to put a symmetric edge on a blade which is not: only problem, it doesn’t work. Left-handers still will have produce sticking on the left face, for right-handers it is a suboptimal edge. The edge won't be in line with the blade's axis.
The same with a proposed 'adapted' edge by the retailer's 'master-sharpener' who will at a moderate tariff miraculously change the knife into one suited for left-handers. A sharpener cannot change the knife's fundamentals. The poor food release, or more exactly the sticking will remain. Apart from all kind of steering and wedging problems that will occur later, when the knife gets slightly thicker behind the edge, unless the owner is himself a very experienced sharpener.

 

[Bolek]

Is there any special tric to sharpen a right handed Misono Swedish?

 

[Benuser]

Is there any special tric to sharpen a right handed Misono Swedish?

There are probably hundred methods, this is just how I do. There is a little problem with its factory edge: weak and overly convexed by excessive buffing. Therefore it's no good idea to just follow the factory edge, which in many other cases is a reasonable approach.
I would try to let the right bevel form one continuous arc with the right face, and be somewhat convexed, ending at about 10-12°. As for the left side, much depends on how used you are to compensate steering. You may choose for a very narrow straight bevel of 15‐18°. If steering isn't that much a problem to you you may convex it as well, by thinning behind the edge on the left side, and keep the angle a bit lower.
How I proceed: I start by thinning behind the edge at the right side at a very low level, and go on until a fat burr got raised, and deburr the left side at the angle I have in mind. Starting with a 320. A fat burr, because you want to make sure the fatigued OOTB edge got really removed. I use a sharpie and a loupe to verify. Raise an equally fat burr on the right bevel. You don't want to move the edge.
Recent 240 Swedish Carbons come much fatter OOTB than they used to in other times. So, there is a bit more work to start with. That said, I still like them a lot. Remarkable F&F and an exceptional regular grinding. Don't forget to ease the right side of spine and choil. Two minutes with a piece of sandpaper are all you need. Enjoy your Misono!

 

[Bolek]

Thanks

 

[Benuser]

My pleasure! To give an idea of the geometry I've in mind, here, very fat but clear, a Misono Swedish Yo-Deba.