Kato geometry

[mark76]

I was wondering what you impression is of the geometry of a Kato knife. They are usually described as convex, but I view many of their geometries as full flat grinds. I realize they differ somewhat due to being handmade, but still..

This is my Kato:



On the left side it is somewhat (slighty) convex, on the other side it might even be concave.

What are your experiences?

 

[Asteger]

I think if you look at Kato from heel to tip you miss the boat, because the geometry isn't consistent along the blade. It's more convex in the middle and less so at heel and tip. Perhaps you see a flat grind looking right at the heel, but that doesn't capture it.

I'll re-use something I wrote earlier, although you contributed on that thread too and maybe have already read it:

... the grind is inconsistent. I haven't really heard people say this aside from talk of Kato 'hoodoo-voodoo' .... I don't mean inconsistent as in 'bad' and under/overground. Rather, on the front/right side I think the convexity is more pronounced and seems to come closer to the edge in the middle of the blade, with less convexity towards the heel and tip, and so when the knife goes through food ... there's this sort of 'V' wedging effect ... pushing food away from the middle of the blade to either end, in addition to just away from the blade ... You see it when you thin and your stone rides up much higher around the heel especially when compared to the middle ...

 

[XooMG]

 

[Asteger]

Photos and no words :scratchhead: so profound ... Nice demonstration and, yes, very convex there, definitely

 

[Matus]

The one in my possession looks like the photos above - strong convex.

 

[Chuckles]

Many knives that are described as convex or very convex have most of their convexity on the edge half of the blade face and are noticeably flatter up on the spine third of the blade face. The convex grind on a Kato starts at the spine and as a result is more subtle in appearance. At least that is how I see it.

Here is a Mizuno Honyaki to compare.

 

[spoiledbroth]

that being said the "left" side of mark's photo (technically that'd be the right side of the bade..?) does display a convexity that I'm able to see.

I like XooMG post haha not many words needed there methinks...

 

[XooMG]

Sorry for the rushed pic.

 

[spoiledbroth]

this thread has risen to the level of pornography

 

[mark76]

this thread has risen to the level of pornography

Nothing wrong with that, I guess, with the number of knife lovers here .

Thanks gents for your pictures. If anyone has more of them: highly appreciated!

 

[Matus]

I only have a choil shot at the moment, I could take a few more photos that show the bevels if necessary

Kato next to prototype Sakai Takayuki Siousin (swedish stainless) - I find the difference quite striking - two extremes one could say.

 

[spoiledbroth]

Holy cow - two extremes - you can say that again!

 

[mark76]

Thanks again, gents. I repeated Roberts "trick" with the ruler. And guess what? My Kato is convex on both sides. It gets more convex towards the middle of the blade. And the right side is a bit more convex than the left side. Choil shots can be deceiving...

 

[Benuser]

I don't understand. XooMG shows a convexed left face, on Mark's figure it's concave.

 

[Asteger]

I don't understand. XooMG shows a convexed left face, on Mark's figure it's concave.

Hard to tell in a photo, but at heel the geometry is quite different from mid-blade where it is very convex on the front side. Have a look at my first post above. I don't know what to call it ... the 'V grind' maybe? as when facing the front side it has that sort of shape, pronounced convexity mid-blade which tapers off toward the heel and tip. This has to be the 'secret' to the good performance of such a fat blade. On the front side, food's pushed away from the blade but also away from the middle of the fat spot 'V' towards the heel and tip. I don't remember anyone noticing or explaining this before, maybe because we tend to imagine geometry will be similar along the length of the blade

 

[Asteger]

I don't understand. XooMG shows a convexed left face, on Mark's figure it's concave.

Hard to tell in a photo, but at heel the geometry is quite different from mid-blade where it is very convex on the front side. Have a look at my first post above. I don't know what to call it ... the 'V grind' maybe? as when facing the front side it has that sort of shape, pronounced convexity mid-blade which tapers off toward the heel and tip. This has to be the 'secret' to the good performance of such a fat blade. On the front side, food's pushed away from the blade but also away from the middle of the fat spot 'V' towards the heel and tip. I don't remember anyone noticing or explaining this before, maybe because we tend to imagine geometry will be similar along the length of the blade

... Here, this might help explain it a bit more and dispell some of the Kato 'hoodoo-voodoo'. Sorry for the simple graphics, but it goes something like this:

 

[CrisAnderson27]

... Here, this might help explain it a bit more and dispell some of the Kato 'hoodoo-voodoo'. Sorry for the simple graphics, but it goes something like this:

This grind is an evolution of what you get when a guy who makes Japanese swords starts making kitchen knives, :wink:

 

[XooMG]

Maybe when I have some time, I'll show mine from heel to tip. Mine is not totally uniform, but it doesn't vary immensely.

 

[mark76]

I think that's a pretty good explanation of the grind, Asteger. Though to complicate matters the left side is a bit different from the right side (at least on my Kato).

 

[F-Flash]

Kato kikuryu gyuto 240mm

And comparison with toyama gyuto with same handle. Kato weights 277g, toyama 227g.

Kato

Toyama

 

[icanhaschzbrgr]

some more pictures of 180mm Kato (near the heel, mid blade and near the tip):

left side:








right side :








I needed to repair a few big chips on the edge once and had to thin the blade afterwards. While on the stones I immediately noticed much more pronounced convexity on the right side.

 

[Benuser]

Thanks, guys.

 

[Asteger]

This grind is an evolution of what you get when a guy who makes Japanese swords starts making kitchen knives, :wink:

Hi Cris - curious to know more about what you meant by this. Obviously you meant it in a good way, that Kato's well-informed by his sword background. However, does this kind of 'v' grind have a precedent in swordmaking?

I don't know, but can't imagine it would. I'd be surprised as Kato gyuto/petty seem designed so that stiffer, thicker knives can be made, but with a different sort of geometry & food release dynamic to compensate for the thickness. I can't think of another knifemaker or sword/knife-maker that takes this approach with gyuto/petty and I've also been surprised for a while that it wasn't more openly discussed here. There are loads of knives out there I'm not familiar with, though.

More generally, would be interesting to hear insights on why people imagine Kato went this route. (A few KKF members have visited Kato, though maybe were unable to communicate other than watch.) For example, I wonder if this approach might be harder to grind, considering that others don't seem to do it this way. I think there's also the issue that the geometry might be harder for users to maintain over time, partly also because the geometry's unconventional and less obvious to the user. I've said elsewhere that maintainability is not really discussed often and so seems an under-appreciated characteristic of good knives, if you consider that good ones should function well and require easy maintanence over the years.

 

[XooMG]

(removed to avoid conflict)

 

[Asteger]

(removed to avoid conflict)

XooMG, you often post this instead of comments, so not sure why. Discussion here so would be interested in your ideas

 

[CrisAnderson27]

It will be difficult for me to reply in any depth due to my position in this forum, but I will try.

Yes, it was meant positively. His geometry/grind is absolutely based off of his sword making experience. I only know one other maker who is using similar concepts and education/experience, though he is applying them a bit differently.

It's also not a 'v' grind at all. The curvature in the sides of the blade is called 'niku', and how the blade cuts is absolutely a function of it. Even completely dull that blade will still cut better than many (if not most) sharpened knives. With an edge it's something else entirely. A good maker will often check his blades by cutting food before putting an edge on them for that very reason. If it won't cut cleanly before sharpening (and by 'cleanly' I don't mean drop through a tomato, though with a proper grind on it before sharpening it may actually do that), then the edge is just a band-aid/crutch for an inferior knife.

As for maintainability, you're right in some ways. Thinning should be performed in a different manner than you would on a typical 'v' grind knife as you put it. More of a blending than a true thinning, and starting higher on the blade. Most guys in the kitchen knife world think of everything in terms of flat angles. Sharpening/thinning is strictly a matter of scrubbing away on a stone while holding the spine of the knife at a precise distance from the stone. Thinning this is a bit different, but everything in this world is a compromise. That's one I think is well worth it.

One last thing. If you want to check the grind on a blade, hold it horizontal in a dim room, pointed towards a set of blinds or other horizontal light source. With a sword you can do so like this:

With a kitchen knife, it's likely too thin (yes, even a Kato lol) to do it like that, so you would do it as I explained above:

You can learn the same amount about a sword by doing the same thing. If you tip it up and down in the light, you can see the reflection of the blinds change along the blade, showing you how the grind changes.

Hopefully that helps fill in some blanks.

 

[MAS4T0]

What you're seeing is "niku" literally "meat" which refers to a cross sectional geometry best described as appleseed shaped. Imagine an appleseed with the pointed side down compared to the diamond like shape you usually see on knives.
This isn't convex bevels, but full face convexity (or rather up to the shinogi). This is vital on swords as it supports the edge on off angle cuts, helping to prevent bending or breaking due to lateral stress (as it allows the blade to be THICK behind the edge without wedging).

Edit: Chris, how would you sharpen a kitchen knife with full niku? Is it a case of "polishing" the blade (as in the case of nihonto) and then adding a (micro)bevel below or is the blade sharpened as one would ordinarily sharpen a kitchen knife.

 

[Matus]

I am wondering whether we do not see here a tendency to 'overthink' the matter at hand (and I mean that only as personal opinion of someone with still rather limited experience and knowledge). It is obvious that the Convex grind of the Kato (and probably some others as well) knives is a complex one - the curvature of the convex grind chances quickly from edge towards the spine. Of course - such a transition only becomes more obvious and observable in actual use with not too thin knives. I would also add that while I find the cutting abilities of the Kato to be good, it is a knife that wedges rather easily, at least in my experience with one. It is the relatively large weight of the knife together with strong front-forward weight distribution that is up to large part responsible for its cutting properties. If the knife was half the weight, I doubt it would be too enjoyable to use.

Just my honest, personal opinion.

 

[spoiledbroth]

I was wondering if someone could help me understand the Kato "v grind"...


I saw Asteger's picture: I was wondering if the picture implies that the knife is ground more thinly at the tip and heel than in the middle?

 

[CrisAnderson27]

What you're seeing is "niku" literally "meat" which refers to a cross sectional geometry best described as appleseed shaped. Imagine an appleseed with the pointed side down compared to the diamond like shape you usually see on knives.
This isn't convex bevels, but full face convexity (or rather up to the shinogi). This is vital on swords as it supports the edge on off angle cuts, helping to prevent bending or breaking due to lateral stress (as it allows the blade to be THICK behind the edge without wedging).

Edit: Chris, how would you sharpen a kitchen knife with full niku? Is it a case of "polishing" the blade (as in the case of nihonto) and then adding a (micro)bevel below or is the blade sharpened as one would ordinarily sharpen a kitchen knife.

Honestly it's easier to just maintain a primary bevel like most knives...so you would sharpen normally. If the maker did his job though, the bevel will be very thin, very durable, and easy to maintain for a very long time just stropping with high grit touch up stones.