(How) Would You Re-Grind this Blade?

[Cushing H.]

It appears that my choice of title for this thread was unfortunate. When I wrote "How", I meant "what geometry would you shoot for", NOT how you would technically grind the thing. I have absolutely no problem or hesitancy with doing this freehand on my grinder and keeping things sufficiently cool - I was only asking a question about what final appearances did the group think would be most appealing. I still think I would prefer to walk the shinogi back a little bit to create a more shallow primary bevel - but I will heed Stacy's advice to keep the shinogi where it is. I will post photos when done.

 

[Richard338]

Since you like the knife, I would use it as a pattern and make 2 or 3 yourself.
I made three nakiri and finished them a few weeks apart. Each one thinner than the last. The last one is certainly best.
You can pick an interesting steel and test some grinds. That shape of blade is about the easiest grind that there is, at least for me.

 

[Cushing H.]

Since you like the knife, I would use it as a pattern and make 2 or 3 yourself.
I made three nakiri and finished them a few weeks apart. Each one thinner than the last. The last one is certainly best.
You can pick an interesting steel and test some grinds. That shape of blade is about the easiest grind that there is, at least for me.

Thanks Richard. I actually already have a couple modified Nakiri blanks that I want to try out to see which I like better .(the mods are somewhat longer for slicing, and somewhat wider for "scooping" of food, which I do a lot.....

 

[Cushing H.]

Alright folks - here is the result of this little venture. The grind went well: 120 grit ceramic, taking the edge down to 0.004-0.005" (the thinnest I can go without a coolmist ), then 220 grit ceramic, followed by A100 and A65 gators. During that grind, I barely nudged the shinogi at all. A "warning" to anyone who tries this (and you will see this in the photos below) - although protecting the blade with duck tape sounds like a good idea - I would NOT do so.

two reasons: it is REALLY hard to get the adhesive off of the blade in the vicinity of the shinogi. After multiple tries of fingernail pushing, goo-gone adhesive remover, really hot water, etc, I had to resort to scrubbing the stuff with a green scrubbie. two results: some scratches on the bevel (removed by minor touch ups with 120grit and up belts), and damage to the Kurouchi finish near the shinogi, which resulted in the need to push that shinogi back just a little in a couple areas to improve the look a little.

The second (the biggest reason), the adhesive on the duck tape is so aggressive it actually lifted the Kurouchi off of the blade in large areas on both sides of the blade. I would not have expected that the Kurouchi would be THAT delicate! I am not going to cry about this (all knives have history) and this is now part of its story - but others doing something like this should be forewarned. It is curious that anything unexpected here did not happen during the grinding - but was due to other stuff :-( . Photos below. (this knife is now sharper than it ever was...




You DO realize, though, that this now begs the question of whether I do a light flat grind to get rid of the Kurouchi while keeping some semblance of the makers mark. But that is a different discussion.....

 

[milkbaby]

I know you already did it, but IMO nakiri are typically thin already, so no need to grind the shinogi line a lot higher unless it had been sharpened enough times to lose a lot of height from cutting edge to the spine.

 

[Fitzhugh]

On that different discussion... Would it be sacrilegious to restore it with some surface treatment along the lines of cold bluing/room temp black oxide treatment? I'm not familiar with the options, just that they are out there. You'd leave the Maker's mark that way, if that's important.

[Restore is obviously has the wrong connotation but I can't think of a good word].

 

[Cushing H.]

I know you already did it, but IMO nakiri are typically thin already, so no need to grind the shinogi line a lot higher unless it had been sharpened enough times to lose a lot of height from cutting edge to the spine.

the stock is 0.10”, not sure how that compares to your experience.? What kind of primary bevel width in that case do you think would be reasonable in that case (without getting overly nerdy about trigonometric calculations)

serious question ... nothing else intended...

 

[Cushing H.]

On that different discussion... Would it be sacrilegious to restore it with some surface treatment along the lines of cold bluing/room temp black oxide treatment? I'm not familiar with the options, just that they are out there. You'd leave the Maker's mark that way, if that's important.

[Restore is obviously has the wrong connotation but I can't think of a good word].

Honestly, i was kind of wondering about this, but no way i have the background to even guess on this. The kurouchi is bacically decarburization, right? What kind of finish could mimic that

 

[Cushing H.]

On that different discussion... Would it be sacrilegious to restore it with some surface treatment along the lines of cold bluing/room temp black oxide treatment? I'm not familiar with the options, just that they are out there. You'd leave the Maker's mark that way, if that's important.

[Restore is obviously has the wrong connotation but I can't think of a good word].

Honestly, i was kind of wondering about this, but no way i have the background to even guess on this. The kurouchi is bacically decarburization, right? What kind of surface treatment could mimic that? I have always heard the decarburization is really hard ... i would not have guessednit is so fragile.....?

 

[Cushing H.]

Sorry for the double post. My ipad was behaving badly....

 

[Fitzhugh]

I've never used any myself but I think Brownells and Birchwood Casey are the main brands, at least at the hobby level.

 

[Hubert S.]

I have used a product from Jax with great results on a piece of metal and wood furniture. I made some test pieces and found it is really important to clean the steel very well to get an even finish. I could not get good results with the Birchwood Casey gun blue when I tried it, but that was a long time ago and probably user error. I am wondering if there is something that you could use to protect the makers mark from darkening. Maybe you could coat it with nail polish before grinding off the kurouchi and then take it off with acetone after using the gun blue?

How do you like this nakiri? It seems to have a lot more curvature, especially towards the heel, than most knives I have looked at. I am planning to make a nakiri and would like to know what you will change when making your own.

 

[Cushing H.]

I am wondering if there is something that you could use to protect the makers mark from darkening. Maybe you could coat it with nail polish before grinding off the kurouchi and then take it off with acetone after using the gun blue?

If I grind the Kurouchi I would just go for a clean metal finish. There are many out there, I believe, that consider the Kurouchi an inferior finish (certainly, they seem to be much less expensive that their clean metal counterparts. I am going to think about this for a while - see how much looking at the finish bugs me

How do you like this nakiri? It seems to have a lot more curvature, especially towards the heel, than most knives I have looked at. I am planning to make a nakiri and would like to know what you will change when making your own.

I really like this nakiri. It came from the maker with this amount of curvature. I flattened it just a little during this regrind - but not much. Although it may not "look" as nice, I tend to like more curvature than less because, with repeated sharpenings, it is easier to avoid creating concave sections on the blade. Also, I consciously try to use more "slicing" motions than up and down "chopping" motions because slicing just cuts the food better and easier. With that slicing motion, with a little bit of rocking of the blade at the same time, the edge curvature is a non-issue. re. balance" most of my japanese knives have magnolia handles, whereas this one has a heavier wood more like a dense tropical. I like the feel and balance of that heavier handle much more than the magnolia handles. If I have any concerns with this nakiri, it is that its length sometimes does not allow me to take a single long pull stroke when slicing. As an experiment I created a pattern which I have described as a "modified nakiri" - slightly longer and wider blade (image below). longer to allow more slicing motion, wider to facilitate scooping up of cut food. I made one of these for my son, and this second blank I am going to grind and try for myself. I really do not know whether I will like the feel of this modified version better or worse than the typical pattern though..... Not sure if that helps you?

 

[Cushing H.]

I am planning to make a nakiri and would like to know what you will change when making your own.

Hubert - just a couple more thoughts re. "what I would change". I have really moved more towards reaching for a different knife, depending on what I am going to do/cut. If I am prepping a relatively small amount of vegetables, I go right for that nakiri. If I am prepping a large amount of vegetables, I reach for a chinese cleaver (similar to the nakiri, but bigger in all dimensions.). If I am prepping meat (or tofu) I will reach for a santoku. So, if you follow that kind of pattern, the existing design of that nakiri is great, if you are doing relatively small prep jobs. for me though, I would keep the handle on the heavy side (the modified version above has a western handle, which was for my son - i personally prefer the Wa "D" style handle..... Again - I hope that helps a little.....

 

[Hubert S.]

Cushing, thank you for all the details. I have some 2" wide stock (1/16" AEB-L) that I was planning to use. I don't use a heavy cutting board, so I just lift the board and slide whatever I am cutting into a bowl or directly into the pot or pan. I have a bench scraper for scooping but hardly every use it for anything other than dough.

I drew a pattern for a nakiri a little while ago with very little curvature. I have since googled a little bit and found a post by Stacy where he recommended some curvature. It makes sense. I am still a bit unclear about how to grind the bevels on such a thin knife that is about 2" wide.

I just finished a santoku knife that is very light and has a really light wa handle. I have not used it much, so I don't know whether I will like the light handle. All my other knives have heavy handles and much thicker blades.

 

[Cushing H.]

e. I am still a bit unclear about how to grind the bevels on such a thin knife that is about 2" wide

I am not sure if this will answer your question, but lets try this. I have ground some pretty thin stock 0.06”), and so have faced the same question. What i have done is start the 45 degree bevel, then start walking it back down the blade, keeping the bevel flat and keeping the shinogi straight (and not grinding out the edge). There comes a point where the angle between the bevel and the flat is so shallow that you start getting some grind lines on the flat even though you are actually flat on the bevel. At that point i keep the shinogi where it is, shift to 120 grit and concentrate on thinning the edge while making sure the bevel is truly flat (this takes a while) Once the edge is thin enough (i currently shoot for 0.005” - i dip often and spray water on the belt, but do wish i had a coolmist), i then blend the bevel and flat at the (now somewhat uneven) shinogi at 120, then refine the entire surface finish (flat and bevel) with 220 ceramic, then A100 and A65 gator belts, all the while blending at the “line” between bevel and flat. In the end, the angle between the two is so shallow, you have to look hard to see it...

is that an answer to the question you were asking?

(oh, and on that thin stock, watch your fingertips versus the belt when you supporting the spine of the blade!)

 

[Hubert S.]

Thanks, that helps. If you had to put a number on it, how far from the edge would you say the transition occurs?

I did something similar on a knife I made for cutting German noodles. I flattened the bevel on a diamond plate and used Gator belts and then a Scotchbrite belt. I did this with the belt running the long way and rocking from flat to bevel. Blending everything worked really well.

 

[Cushing H.]

Oh i am not sure i can say (i dont have those blades here). It definitely depends on the thickness of the blade though (the thinner the blade the closer to the edge is the transition). Sorry...

 

[Hubert S.]

No worries. I am just going to try one and see what happens. Unfortunately, your method of waiting for the scratch marks on the flats to appear won't work for me, as that pretty much happens at random times when I grind... I've got to practice grinding.

 

[Cushing H.]

No worries. I am just going to try one and see what happens. Unfortunately, your method of waiting for the scratch marks on the flats to appear won't work for me, as that pretty much happens at random times when I grind... I've got to practice grinding.

Ah, yes ... the "feel" of grinding. at least for me, what works and makes sense is - first establish the 45 degree bevel off of the edge (but not quite to the center of the edge). then, carefully and slowly set the blade against the belt with the edge tilted towards the belt (so the edge contacts the belt before the bevel). then, keeping the edge in contact with the belt, rotate the spine towards the belt. There will come a time where the edge of the blade lifts ever so slightly away from the belt. Start grinding with pressure there, and you will walk the bevel back towards the spine a little. rotate back so that the edge just barely re-contacts the belt, and you will be grinding down the same flat bevel. At least I have found taht as the bevel gets a little wider it becomes easier to do this to get the bevel flat against the belt, then a little pressure on the other side of the blade (just opposite from where the bevel contacts the belt) is enough to keep that bevel flat against the belt as you do your pass. pressing a little higher grinds more towards the edge, pressing a little lower lengthens the bevel a little. just dont press too low, or twist too much with the other hand and you stay on the bevel, and dont unexpectedly grind on the flat. In a way, doing this "locks" the bevel against the belt..... (many others have talked about this earlier - but that is how I can describe what finally "clicked" for me)

Now, I am definitly not up to creating a razor sharp shinogi, but every blade I grind I practice on keeping that shinogi (line between the bevel and the flat) as sharp and even as I can. I definitely have a long way to go on that (especially, as you said, with thin stock). Natlek says you just can not do it unless you use a jig. Perhaps, but for now grinding freehand just feels much more natural to me. So..... for now I am sticking with full flat grinds, or the shallow "blended" grind we discussed above

I have a knife that is still in glue-up for the Wa handle that was really thin stock and a bear to grind uniformly - I will post a photo of it to this thread for you to look at it when I am finished with the handle....