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Let's talk about symmetry!

Mon Apr 28, 2014 8:42 am

As far as I came to understand, when it comes to (a)symmetry, most of the gyotos, santokus, nakiris, pettys and other knive types on this site are ground 50/50, with some lines being exeptions to confirm the rule. I also believe this collection to be a rather large and thus representative one.

Am I wrong?

Because if not, this article is quite confusing for me, stating that pretty much every japanese knive is ground asymmetric, mostly 80/20, 70/30 or 60/40.

Please help me clarify this, because I am very confused :)
Thanks.

Re: Let's talk about symmetry!

Mon Apr 28, 2014 1:19 pm

It's easy enough for you to see for yourself. Use a carpenter's square or straightedge on both sides of the knife to allow you to see the differences between the way the knife was ground. You are not looking at the cutting edge, but at the overall grind of the blade. I almost every case, you'll find that the right side is more convexed than the left. In fact, some knives may have no convexity on the left side. It is very rare to find a Japanese knife with perfect symmetry. Generally, the thinner the blade, the less effect asymmetry has on either use or sharpening. On some knives, like the Suisin INOX Honyaki series, it is very hard to see the asymmetry at all.

Now look at the cutting edge. It may be hard to see, but usually the edge bevel on the right side is slightly wider than the one on the left, but more importantly, it is usually ground at a slightly different angle in relation to the spine of the blade as well, following the asymmetry of the primary bevel.

What does this mean for the user of the knife? Well, in cases of extreme asymmetry (as in 90/10 or 99/1), the knife may exhibit "steering", or pulling to one side when cutting. Mild asymmetry has little discernible effect on cutting.

As far as sharpening is concerned, the preferable method is to follow the bevel angles that the knife came with. You can best see this when first sharpening the knife by using a magic marker on the bevels so you can judge the proper angle. This preserves the and keeps the blade at peak performance.

You can also just sharpen at any arbitrary angle, putting the same angle on both sides of the blade, and you probably won't notice any major change in the knife's performance, although it will exist. Most sharpeners do this, and most don't perceive the difference.

Bottom line? Don't be overly concerned with asymmetry when purchasing a knife. When you get it, try to preserve the asymmetry, but don't make an issue of it unless your knife starts to exhibit steering.

Re: Let's talk about symmetry!

Mon Apr 28, 2014 1:26 pm

+1 to Rick's entire post.

Mowgs.

Re: Let's talk about symmetry!

Mon Apr 28, 2014 2:10 pm

Yeah, can't really do much but +1 Rick's post.

Re: Let's talk about symmetry!

Mon Apr 28, 2014 3:25 pm

I cringed when I read the first post but Rick provided a sensible and data-driven discussion. Great job!

Re: Let's talk about symmetry!

Mon Apr 28, 2014 10:34 pm

Thanks a lot for the clearup. Does a slight asymmetry mean a difference in performance when used by a leftie? Should you look for knives ground "the other way round" when your left handed?

Re: Let's talk about symmetry!

Mon Apr 28, 2014 11:32 pm

Brainless wrote:Thanks a lot for the clearup. Does a slight asymmetry mean a difference in performance when used by a leftie? Should you look for knives ground "the other way round" when your left handed?


I'm not left-handed, so I can't speak from personal experience, but my left-handed wife says there is none.
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