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View Full Version : how to fix shinogi line and uneven blade geometry?



jgraeff
05-13-2013, 01:23 PM
Hey guys i have a single bevel blade that i got off Jbprince a long time ago before i even knew what a single bevel was. I remember being in horror when i went to wipe the garlic off the backside of the blade only to find my finger in shreds haha.

anyways the shinogi line has never been straight and if you look at the edge it almost looks warped like its at a slant, however the spine is perfectly straight.

i have tried with a marker to hit certain spots and fix it. i have made it better however its still not how id like it to be. i always make sure to lap my stones and rotate through the process with single bevel.

I cant seem to get this right no matter how hard i try, i spent about an hour the other night and to no success. On another note the thing takes and extremely scary edge even of a 2k stones.

http://farm8.staticflickr.com/7298/8734820011_e0e57cf7f1.jpg (http://www.flickr.com/photos/93646376@N06/8734820011/)
IMG_6269 (http://www.flickr.com/photos/93646376@N06/8734820011/) by jgraeff2 (http://www.flickr.com/people/93646376@N06/), on Flickr

http://farm8.staticflickr.com/7299/8734819555_dba325237d.jpg (http://www.flickr.com/photos/93646376@N06/8734819555/)
IMG_2084 (http://www.flickr.com/photos/93646376@N06/8734819555/) by jgraeff2 (http://www.flickr.com/people/93646376@N06/), on Flickr

http://farm8.staticflickr.com/7320/8734818699_bb11862ae7.jpg (http://www.flickr.com/photos/93646376@N06/8734818699/)
IMG_3062 (http://www.flickr.com/photos/93646376@N06/8734818699/) by jgraeff2 (http://www.flickr.com/people/93646376@N06/), on Flickr

i am giving this to snowbrother to help him was hoping to fix it a bit first. any suggestions

mhlee
05-13-2013, 02:24 PM
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.

jgraeff
05-13-2013, 03:34 PM
i will leave that up to him i got the knife for like 50 bucks and i didnt know much about it, havent used it since culinary school and only been sharpened yesterday when trying to fix it, it was sent to me like that but i never thought anything of it back then.

It works very well i know that going to send it out to him and see if he can utilize it for now, hopefully he can fix it himself.

Mike9
05-13-2013, 05:37 PM
The shinogi line does no work - the cutting edge does - but you knew that. In other words I doubt that the cutting edge cares what the shinogi line is doing. I have discovered that it is purely aesthetic on some level.

Jmadams13
05-13-2013, 05:49 PM
I agree with mike. Some of my best cutters have lines like a blind monkey was doing the grinding

xuz
05-13-2013, 06:04 PM
I agree with the previous posts, but as a general practice when you send your knives in for professional Japanese sharpening services,
is bevel work included in basic sharpening?
Or do you have to specifically ask for refinish up to the shinogi?

JBroida
05-13-2013, 06:20 PM
unless otherwise specified, most japanese knife sharpeners will do the entire blade road (from shinogi line down).

cwrightthruya
05-13-2013, 06:26 PM
I agree with the previous posts, but as a general practice when you send your knives in for professional Japanese sharpening services,
is bevel work included in basic sharpening?
Or do you have to specifically ask for refinish up to the shinogi?

This depends on who you send it to. I believe Jon at JKI does it automatically, while others do not.

@jgraeff---As has been said before, a straight shinogi line is not necessary for a knife to function well. You need a straight bevel and a straight edge with good geometry and that is all. You have to remember that the sides of the knife were ground or hammered before the bevel was cut. So, in essence you can have a dead flat/straight bevel while still having a terrible looking wavy/slanted/tilted shinogi line because this line is the function of where the two planes meet.

cwrightthruya
05-13-2013, 06:28 PM
As an example: I have a Nakiri that I know has very straight bevels, and the shinogi line is wavy as hell. But, this was also hand hammered with a karouchi finish.

JBroida
05-13-2013, 06:37 PM
single and double bevel knives will be different in the sense of the shinogi line

cwrightthruya
05-13-2013, 07:05 PM
Very true, I should have said that. I had a Usuba that is the same, but not nearly as bad.

mhlee
05-13-2013, 08:03 PM
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
05-13-2013, 08:58 PM
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
05-14-2013, 02:25 AM
unless otherwise specified, most japanese knife sharpeners will do the entire blade road (from shinogi line down).


I agree

Dave Martell
05-14-2013, 02:27 AM
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.