This is Sukenari (佑成) HAP40 High Speed Tool Steel K-tip (Kiritsuke) Gyuto, with its signature Hairline finish and K&S Teakwood handle.
The HAP40 by Hitachi is a powdered semi-stainless steel, has only about 4% of Chromium. The high Chromium content in stainless steel tends to stick to food and gives a wired sharpening feedback; the HAP40 in contrast behaves like carbon steel yet it won’t rust as easily as traditional carbon steel. One could almost get away with any rust developing on the blade as long as it is cleaned and wiped dry after each prep.
The HAP40 line is heat treated to a staggering HRC 68 +- 0.5. (If you have any double of this, you should read this blog). This is even higher than the Sukenari’s famous ZDP189 line (HRC 66) and the now discontinued Aogami Super Damascus line (HRC 67). You may wonder this is going to be a nightmare to sharpen (since the ZDP189 is bad enough already), but the truth is, it wasn’t that bad. My experience with the Sukenari HAP40 is that it sits between SG2 and ZDP189 in terms of how easy to sharpen. Because the HAP40 is a highly alloyed steel, it won’t be as chippy as the ZDP189 or the water-quenched Aogami Super.
As always, the grind of Sukenari is not the thinnest out there but to me it is still thin enough for most users. The 240 that I tried goes through potato effortlessly, thanks to the super sharp OOTB edge and a very nice geometry. If your task requires an extreme edge retention, the new HAP40 line from Sukenari is a very good alternative (upgrade) to the ZDP189 line.
Tip to Heel Length
Blade Height at Heel
Width of Spine Above Heel
Width of Spine at Middle of Blade
Width of Spine at about 1cm From the Tip
|Hitachi HAP-40 High Speed Tool Steel
|K&S Teak Handle with options