how to fix shinogi line and uneven blade geometry?

[cwrightthruya]

Very true, I should have said that. I had a Usuba that is the same, but not nearly as bad.

[mhlee]

I've only done some minor work on my own single bevel knives, so, I'm no expert. But from what I see, this knife needs a lot of work.

First, the shinogi line is wavy, which isn't such a big deal, but the primary bevel from the edge is seriously wavy. This, based on my limited experience, is because inconsistent pressure was used when sharpening. Single bevel knives, more so that double bevel knives, require a light, consistent touch when sharpening. (The primary bevel and secondary bevel also seem to have been blended, but that's not a big deal from what I understand.)

Second, is how the shinogi line and the bevels toward the tip area have been seriously curved upwards. It looks like a lot more pressure and work has been put toward the front half of this knife and the front inch or so where it appears that there are several different levels of sharpening.

You may want to consider sending this off to Jon at JKI.

I made a misstatement. The wavy shinogi line is an issue. (I recall seeing some new knives with wavy shinogi lines but, I have since been corrected by a person much more knowledgeable than me - Jon at JKI - that this is manufacturer error.)

As I learned from Jon, the shinogi line is how you sharpen the secondary bevel, which, in turn, allows you to sharpen the primary bevel, as you put pressure on the shinogi line to sharpen the secondary bevel, and then, the primary bevel to sharpen the edge. So, the shinogi line and edge should be parallel - if the shinogi line is wavy, you'll end up with a wavy secondary bevel, and then a wavy primary bevel and edge.

Jon also explained how the shinogi line directly affects food release, which makes perfect sense, because the shinogi line is essentially the geometry of the knife.

Sorry for the misinformation.

[tk59]

At that price, you're not going to get something with a perfect grind. More than likely there is more than one substantial flaw in that knife. I wouldn't worry about it unless you were having issues at the edge. There's a good chance that knife will never have a perfect shinogi regardless of who works on it. If it were mine, I'd just use it and practice on it until I decided to upgrade (if I ever got to that point).

[Dave Martell]

unless otherwise specified, most japanese knife sharpeners will do the entire blade road (from shinogi line down).

I agree

[Dave Martell]

At that price, you're not going to get something with a perfect grind. More than likely there is more than one substantial flaw in that knife. I wouldn't worry about it unless you were having issues at the edge. There's a good chance that knife will never have a perfect shinogi regardless of who works on it.

I agree with this also.