Manufacturer: Yoshida Hamono
Blacksmith: Osamu Yoshida
Production area: kyushu, Saga/ Japan
Profile: Kiritsuke Petty
Size: 150 mm
Type of steel: Powder Steels
Steel: Hitachi HAP 40, flexible stainless steel coating
Handle: Stabilized maple magnifying glass octagonal complexion
Total length: 265 mm
Edge length: 142 mm
Handle length at tip: 152 mm
Blade height: 30 mm
Thickness: 2 mm
Handle length: 115 mm
Hand orientation: Ambidextrous
Hardness: 68 HRC
Yoshida Hamono is located in Saga Prefecture, a very rural area of Kyushu Island. Like many blacksmiths in rural areas, they have specialized in making agricultural tools such as sickles and hoes, but they are recognized nationally for their incredible kitchen knives. The first generation of the Yoshida family was, like many, a blacksmith. After World War II, they decided to open a small workshop to produce knives and other steel tools, and in 1971 they expanded to large-scale production to meet a growing demand from all over Japan. They invested very early in modern machines that made large-scale production possible, which is one of the reasons why they have the opportunity to coat their own steel, rather than buy it pre-rolled. Because Saga is not a large knife production center and there are not many other craftsmen, they have built a facility that can fully handle the knife making process from start to finish, while most cutlers outsource their rolling and sharpening of steel.
When the HAP 40 first became available, Osamu Yoshida quickly bought the steel and tried it. He was amazed at how incredibly sharp steel could become and how long it would keep its edge, so he started making kitchen knives using this super steel. Although it is a difficult steel to handle, it feels a great sense of accomplishment when forging with it compared to other steels.
In addition to laminating their own steel, they also treat their knives with sub-zero heat to purify the steel, allowing the knife to work better and sharpen better. This is done after quenching, treating the knives with liquid nitrogen to remove excess retained impurity that has not been converted to martensite. This prevents the knife from bending over time by “stabilizing” its structure. Although this is scientific gibberish for the most part, it is a big problem in the world of knife making.
The secret of this knife lies in its hard core made of a somewhat exotic Hitachi HAP-40 steel, which falls into the category of modern and technologically advanced steels. The HAP-40 is thin enough to sharpen very well, and knives made from it retain their sharpness 3 to 5 times longer than traditional knives. An interesting fact is that, since it is a powdered steel, it has a very low chromium content (about 4%) and can react like a high-carbon steel under specific circumstances.
This steel is heat treated to an incredible 68 HRC, but it can still be sharpened relatively easily on sharpening stones. It is extremely strong and therefore less likely to flake along the edge than the steel used in traditional knives.