Wide bevel vs convex sharpening: What's the difference if the blacksmith is the same?

[josemartinlopez]

There were two Tanaka gyutos that just sold here:

Hitohira Tanaka Kyuzo Blue #1 Kurouchi Gyuto 240mm - SOLD - Hitohira Tanaka Kyuzo Blue #1 Kurouchi Gyuto 240mm

Brand: Hitohira ひとひら (一片)
Smith: Tanaka Blacksmith 田中打刃物製作所
Producing Area: Sakai-Osaka/ Japan
Profile: Gyuto
Size: 240mm
Steel Type: Carbon Steel
Steel: Yasuki Blue (Aogami) #1, Soft Iron Clad
Handle: Taihei Ebony & Buffalo Horn Ferrule Octagonal
Total Length: 386mm
Edge Length: 228mm
Handle to Tip Length: 238mm
Blade Height: 51mm
Thickness: 2.1mm
Handle Length: 142mm
Weight: 201g
Hand Orientation: Ambidextrous
Sharpener: Kyuzo 久蔵
Handle Maker: Taihei 太平

Hitohara Tanaka Yohei Blue #1 Kasumi 240mm Gyuto - SOLD - Tanaka x Yohei ,Blue #1, Kasumi, 240mm Gyuto - Cherry Wa Handle

Brand: Hitohira ひとひら (一片)
Smith: Tanaka Blacksmith 田中打刃物製作所
Producing Area: Sakai-Osaka/ Japan
Profile: Gyuto
Size: 240mm
Steel Type: Carbon Steel
Steel: Yasuki Blue (Aogami) #1, Soft Iron Clad
Handle: Cherry Wood & Ebony Ferrule Octagonal
Total Length: 384mm
Edge Length: 224mm
Handle to Tip Length: 238mm
Blade Height: 48mm
Thickness: 2.6mm
Handle Length: 144mm
Weight: 177g
Hand Orientation: Ambidextrous
Sharpener: Yohei 与平

Both Tanakas in Blue #1, so the difference is the sharpener. Specifically, the Kyuzo is wide bevel and the Yohei is convex. I've been trying to understand this and the old threads on this. What is the difference exactly? In this specific example, how would the two Tanakas end up different?

 

[ian]

Convex means the geometry is continuously and smoothly convex from edge to spine. Wide bevel means there’s a sharp angle change somewhere up the blade, called the shinogi line. The “wide bevel” is the part below the shinogi, and you can see the difference in the picture. Below the shinogi, the geometry of the wide bevel can be convex, flat or concave. The Kyuzo usually comes concave out of the box, I think: they grind the whole wide bevel on a big wheel, so the convexity of the wheel becomes concavity of the wide bevel. IIRC, the seller had made the wide bevel convex before selling, though.

The difference between a convex ground knife and a convex wide bevel knife, though, is the sharp shinogi line, and the fact that the amount of convexity of the actual wide bevel is usually pretty mild.

In terms of cutting feel, a wide bevel will often be very thin behind the edge, and so can pass through product pretty easily, although if the product is very tall and the knife is not so thin at the shinogi, it’ll start to wedge. More agressively convex knives like the Yohei have better food release in general, although food can slide off a wide bevel knife as it passes the shinogi, which can also help with release.

In terms of the knives above, the Yohei is also lighter and you’ll probably feel that in use. Not sure where the balance points are, though, which makes a big difference.

I have a Yohei in white #1 and really like it.

 

[josemartinlopez]

Thanks for a really well written answer! As a side question, how do you gauge the price difference in the two knives in our example? Is it just because the Kyuzo had a recognized sharpener and better handle and finishing?

 

[ian]

The Kyuzo has a *more expensive* handle. They do seem to sell for more than the Yohei’s for some reason. I don’t know why, though. Both Kyuzo and Yohei are pseudonyms, to my knowledge. (Please correct me if I’m wrong, people.) Pricing is confusing to me.

 

[josemartinlopez]

No, check the link, Hitohara describes Kyuzo as a specific person and son of a famous sharpener.

 

[ian]

Dunno, still may be an alias. Hitohira has a habit of giving their people aliases drawn from the movie “Seven Samurai”, and both Kyuzo and Heihachi (his supposed father) are names from the movie.