A new prototype Gyuto just off the grinder. Thoughts?

Here is my latest prototype. I've been thinking about this for weeks and just couldn't wait to get to it.
Finally got my batch back from HT and this is the first thing I wanted to make.

This is a double hollow each side. It's light and thin, almost laser like, but should have very good food release on the board.

I have to say this took every bit of skill I had and then some. I used flat, convex, and hollow techniques in one blade. Just crazy difficult.
And belts, good grief this dulled 10 belts at least from 40 to 220. Every bit of it required fresh sharp belts or the blade would skitter around.
Took me three sessions this week to get it here.

So I would love to hear comments from makers or chefs on the attempt.
Don't hold back. I love a critical eye and a bold keyboard.

First session, the lower hollow.

 

I am not a chef nor a maker but I love the concept. Could you give us some more details on the geometry? It is hard to see how much hollow it is. How thick is it at the maximum thickness at mid blade and how much a minimum of the upper section?

I am also very curious how you are going to finish that: I except it to be a pain sand.

 

Looks very, very interesting. I'd love to take it for a test drive!

 

It is a bulk idea. "Double hollow each side" do you get this idea from a dragger? Would like to see how it perform compared to other grinds like simple convex, asymmetric convex, S grind etc. It would also be interesting to see the difference in performance between double sided double hollow and single sided double hollow.
Thanks

 

It has already been done for kitchen knives. See for instance the both excellent reviews of the Van Zanten knive by @mark76. https://www.kitchenknifefora.com/threads/review-of-top-damascus-gyuto-by-johan-van-zanten.4142/
Very interesting reading. Still it is faaaar from being common. Moreover, it seems that everyone agrees on the difficulty of achieving such a complex grind.

 

The standard geometry measurements are:

Taper from 2.3mm to 1.6 2 inches from the tip. Tapering to .4mm just off the tip, but this will be reduced further in sanding. The entire 3 inches of tip will likely be reduced further for tip slicing. I am still working that out. I need to test because the hollows should reduce resistance, so unsure at this point if further thinning is necessary.

.005 at the edge and stays thin behind the edge up the blade due to the hollow coming right to the edge. The ridge where hollows meet is .03 inches approximately or .72mm. It varies the length slightly +/-
Above the ridge the blade again resumes a very gradual increase in thickness up to the spine.
The hollows never dip below but maintain always a gradual increase in thickness.
This one is 190 mm heal to tip.

The grind is slightly asymmetrical, favoring the right, with the left mean bevel reduced as compared to the right.
This should work well with everything but butternut and the like. It is probably not going to split a pineapple well.

There are indeed others making a similar grind. The differences might be that I didn't run the top hollow off the edge except toward the tip (taper). I wanted to maintain a fair spine, but without being too thick.

The driving force in design is food release for the hollows, with ease of pass through in the thinness. Suntoku, your single sided d-hollow is an interesting idea. Somewhat Yanagi-like. That might be worth a try at some point.

I can understand why this isn't a common grind. I am sure the process will get faster, but this is a very difficult one and may not lend itself well to production knives.
I have to add a disclaimer on this one. This isn't going to be a for sale / perfect F&F knife. It is a true concept knife for testing the geometry. That said, I would really like to pass this around to the pros here and see what the consensus is.
I hope to have it finished in the next week.

 

It is crazy thin altogether! It is going to fly through food. Very nice.
I follow this. Definitively. With such a geometry also, it is a knife that will require experienced user: it is less robust than a convex I guess.

 

I concur in all accounts Zietum. I generally prefer "meatier" knives rather than lasers, that said I have a very thin one from Mark and it's extremely fun to use. And the tip, oh the tip is a ghost but I think it's certainly more catered towards careful/experienced users.
I think this double hollow concept seems very interesting and difficult to execute, will probably require some testing and tuning before it reaches its full potential but that prototype looks very interesting already. It's interesting how the convex between the two hollows resembles where the convex "meat" of the Kato grind is located (albeit this is a very thin knife ad very different grid all around).

 

Hand sanding about half done. Not nearly as difficult as I thought it was going to be. ...or I am desensitized by the long grinder sessions.

Anyway, it's cleaning up fairly well. Still has oil on it from sanding session...

 

Nice.

 

It is thin and I'm sure it will be a good cutter. It actually went a little thinner than I had hoped. It was hard to say how it would actually come out, even though I tried to draw it out on paper.
I think I am going to work up another one now that I know what I am up against, but I will certainly be testing this one out on some fat carrots and the like to see what it will do.

 

The idea is not new, it's interesting for me to work in this direction, and I like it. These knives are ordered by people who don't like sticking of products. By your favor Mark I'll show how I do it.

 

Those both look interesting. That lower one almost looks like a scandi with a hollow behind it. I'd like to try something like that.

 

I did some unsharpened cut testing with this one yesterday. Not as I expected. Although it cut terrifically, the food release was non-existent on whole potatoes thin sliced. Maybe that's just potatoes. :\
This may end up being my wife's next laser thin blade.
I am going to have to rethink the geometry. Hand sanding did wash out the line a bit, but not terribly.

 

the geometry is not like a scandi but like on the photo

 

That's a pity. Would it be possible that the concavity is not deep enough?

 

Potatoes are a fine test for that one application, but there is little that a thinly sliced potatoes won't stick too. Unless there is a large amount of convexity at the bottom to push the potato away from the blade, it will stick. However, if you have larger convex portions at the bottom then it does not do as well at more dense foods. Carrots, sweet potatoes etc.

I will always argue against fancy "S" grinds, or maybe I have just never seen it work as well as intended. I just don't think what happens in the top third of the blade really matters. IMO, A well placed and executed simply convex surface will do more than a double hollow, S, etc...(and take less time).

 

It did get a lot thinner than I intended, so yes, the concave hollow is not as deep as it might have been.
It's a trade-off between deeper hollows and thin behind the edge.
I have a 14 inch wheel that would go much deeper. I just need to figure out if this still will allow me to hit the other points (thinness).

 

You may very well be right Matt.
I have to experiment though. It helps me to fully understand the nuances. Maybe I get something good, maybe I don't. But I have to try it out.

 

That looks like it would eliminate stickiness for sure Andrei.