Wide double bevel practice knife - zakuri?

[chiffonodd]

I have a kochi 240 gyuto that I adore for obvious reasons. Because of a recent move across state lines, crazy job, and a subpar kitchen in the new apt, I have not had many opportunities to cook with it -- maybe three meals. So it is not in need of sharpening yet and honestly does not feel like it even needs a touch up.

That said, the day is surely approaching when it will. One option of course is to send it to Jon when in need, but I'd really like to work on my own sharpening skills for this sort of grind. But I absolutely DO NOT want to screw up the geometry of this knife, so I want a cheap wide bevel knife to practice double hamaguriba edge sharpening.

I've read a lot of threads, looked at lots of pictures, and visited a lot of interest stores. At this point, I'm thinking Zakuri as a good choice? Can snag a 210 gyuto on rakuten for ~$50 USD + shipping. The grind won't be as sophisticated as the kochi but it will at least provide me with an opportunity to practice wide bevel sharpening - particularly the act of first sharpening with the blade practically flat up to the shinogi, then lifting the spine to hit the edge, and then blending.

Am I on the right track with Zakuri? Or are there other/better candidates out there for this purpose?

 

[Dardeau]

Buy the itinomonn KU 210mm suji. It will end up getting used quite a bit after you get your skills down.

 

[chiffonodd]

Here's some indication of the grind on a zakuri gyuto:

And here's my kochi. . .

Obviously not the same but perhaps enough similarities to be instructive? Also when it comes to refinishing. Want to get into fingers tone too. Next rabit hole :biggrin:

 

[chiffonodd]

Buy the itinomonn KU 210mm suji. It will end up getting used quite a bit after you get your skills down.

Good point. Might as well get something that will fill anothe niche moving forward.

 

[Pensacola Tiger]

It sounds like a good plan to practice with a Zakuri, but neither the Kochi nor the Zakuri have hamaguriba edges, which are typically found on yanagibas and debas, but have a flat, or even a subtle concave grind. Put a straightedge up to your Kochi and you'll see the bevel is not convex.

 

[chiffonodd]

It sounds like a good plan to practice with a Zakuri, but neither the Kochi nor the Zakuri have hamaguriba edges, which are typically found on yanagibas and debas, but have a flat, or even a subtle concave grind. Put a straightedge up to your Kochi and you'll see the bevel is not convex.

Hmm there are a couple threads from Dave and Jon were they talk about sharpening wide bevel knives (even the double bevel gyutos) using a technique similar to hamaguriba for both sides. So that is what I imagined I would have to do with the kochi. But I see you are right and that in fact the kochi even has a bit of a hollow grind behind the edge. I don't see any way to preserve that with stones. So I assume it is best to use the "hamaguriba" technique (term used here loosely, more like blending multiple bevels) after sharpening the wide bevel flat up to the shinogi line, hitting the shoulder a bit to thin, and then lifting the spine to hit the edge, and then blending the two? Some of the hollow grind will be lost over time but what's my alternative?

 

[malexthekid]

I suppose the question to asm is the hollow grind full intentionally or just a result of wide bevel grinding on a wheel?

And i can image an issue with slowly over time changing from slight hollow to slight convex as you keep sharpening. Thougj i onage ot would take quite a while to get there. But i should defer to a better expert.

 

[Pensacola Tiger]

I consider working the wide bevel on a double bevel knife as thinning, at least on the Carters, Moritakas and Tanakas I have used. As you say, I lift the spine to put the actual cutting edge on, though I don't blend it, as there isn't much to blend. I work the wide bevel when I detect a decrease in performance, though some people will work it every time they sharpen (like Curtis, if anyone remembers him from KF).

This same regimen would apply to the Kochi, though the slight concavity might extend the time before the bevel needed to be worked to thin the blade.

 

[XooMG]

No, a hollow behind the edge is not intentional. It is a consequence of the way they grind and finish and will be eventually ground out.

A dead-flat kireba is not optimal in my opinion. A weak convex can be achieved by thinning the first few millimeters behind the edge and blending a little; and progressive thinning and refinishing will enhance it and draw the meat of the convex higher up the kireba. The maker did not program a perfect geometry into the knife, and it can be optimized for different tasks or tastes if you're going to put work into it.

I sold my Kochi, but would have modified it over the course of a few thinnings, had I kept it.

For practicing that kind of modification, the shorter Zakuri are pretty nice knives to learn on...they're rough enough that losing a little kurouchi won't scare you, and good enough to keep when you figure them out. I think the cladding on them is much easier to work with than it would be on some other knives like Tadafusa. Other cheap kurouchi knives can be used, but I was happy enough with the value of the Zakuri knives that I didn't start looking for cheaper Tosa pieces.

However, for just sharpening, this is not brain surgery and you will not mess up the knife or seriously affect the geometry. To seriously change the geometry (and I do this pretty often) takes quite a bit more work than you think. The worst thing you can do is way over-sharpen until the edge is pretty thick and needs slight thinning (not necessarily a bad thing if adding convexity as I said above). I agree if you have zero experience, it is not ideal to attack a very thin edge with coarser (1000-grit or coarser) stones right away. A cheapie gives you a good sense of the rate of metal removal.

To sharpen the Kochi early on, I recommend not letting it get very dull, and do the occasional touchup with something around a 2k to 4k stone. You won't grind off too much and you can focus on your consistency of angle.

 

[chiffonodd]

To sharpen the Kochi early on, I recommend not letting it get very dull, and do the occasional touchup with something around a 2k to 4k stone. You won't grind off too much and you can focus on your consistency of angle.

Thanks for all the advice. With respect to the quoted section of your post above, I assume you're talking about more than just stropping on the 2K - 4K, right? I have a 3K/8K combo stone that I could use to "sharpen" on the 3K with edge leading and then strop on the 8K to finish. Sound about right for what you were mentioning?

 

[XooMG]

I think edge-trailing strokes ("stropping") give a nice spooky feeling to the fingers, but they should be used sparingly to prevent pulling a large burr.

I wouldn't worry too much about specifics; but yes, reset your "sharp" edge with the 3k and do a couple of strokes with 8k to polish or add a light microbevel. It doesn't take a whole lot, especially if the edge is thin.