Tosa cutlery Tosa uchihamono
Free-forged blades crafted by traditional artisans
Quality from years of experience
Tosa Uchihamono are hammer-forged blades produced in an area covering the eastern to central part of Kochi Prefecture, including Ino Town and the cities of Kami, Nankoku, Tosa, and Susaki. Kochi Prefecture was once known as Tosa Province, giving rise to the name of Tosa Uchihamono, but only blades made by following the traditional process can claim to be authentic Tosa Uchihamono.
They are distinguished by free-forging in which shapes are formed by much painstaking hammering and flattening of cherry-red metal. These artisans practicing free-forging can make any size or shape of blade; in essence, they are bespoke blade makers capable of producing a wide variety of bladed-articles in small production runs. As they may be required to make any item ranging from small kitchen knives to full-size forestry saws, artisans spend many years developing their skills. In addition, originally Tosa Uchihamono evolved from practical tools used in forestry and agriculture; therefore, they are renowned for not only their sharpness, but also durability and easy care. The main product range includes kitchen knives, sickles, hatchets, axes, and hoes.
Kochi Prefecture, once Tosa Province, is blessed with an abundance of forests and good quality wood, and from olden times, the region has made the hammer-forged blades needed for tree felling. In 1306, the late Kamakura period, a group of artisans practicing the sword-making skills of Gorozaemon Yoshimitsu moved to Tosa from Yamato Province (present Nara Prefecture) and flourished, particularly in the Warring States period (1467-1568) when they supplied weapons and swords. Over time, the newly introduced sword-making techniques spread to those artisans in the province already making hammer-forged blades for agriculture and forestry; historical documents of 1590 record 399 blacksmiths in Tosa Province. But the full-scale development of Tosa Uchihamono only started in 1621, the early Edo period, when the Tosa domain experiencing economic hardship embarked on the development of new rice fields and the practical use of its forest resources; this revival of the local economy created an increased demand for hammer-forged blades in agriculture and forestry leading to a dramatic improvement of production volume and the quality of blades. The patient trial and error of local blacksmiths at that time gave birth to the Tosa Uchihamono techniques still used today. This tradition, continued from the Edo period, has been passed down through the generations until the present day where artisans are still continuing to develop their craft.
General Production Process
- 1. Splitting Charcoal
Charcoal is split to an appropriate size, but equally important is to ensure the charcoal pieces are of a uniform size to allow accurate control of the fire by feeding air from a bellows to a hokubo furnace; the aim is to maintain a temperature high enough to work steel and iron. It is said to master the skill of splitting charcoal takes three years.
- 2. Preparing Steel and Iron
Tosa Uchihamono is distinguished by a metal inserting process. Firstly, a length of steel for the blade edge is prepared and then a long groove is made along the thin edge of an iron strip and the steel strip is inserted into the groove and lightly hammered. Boric acid is applied as an adhesive and the iron with steel is put into the fire.
- 3. Forge Welding
After heating in the hokubo furnace, it is hammered to weld the two metals together. Sandwiching hard steel between soft iron prevents the steel from breaking. Recently, some production centers use a ready-made combination of steel and iron.
- 4. Forging and Shaping
The welded blade is heated until red-hot and placed on a kanadoko (anvil), where the blade is beaten into shape by using a belt hammer. Kanadoko is a stand used for hammering, and the belt hammer is a belt-type high-speed rotary machine hammer developed in the early years of the Showa period (1926-1989), which has significantly helped increase production volume. After belt-hammering, the shapes of the detailed parts are adjusted with a traditional hammer. This style of hammer work is known as “free-forging” and requires much experience and skill.
- 5. Rough Grinding
The forged blade is ground using a high-speed rotary grinder to create a well-balanced shape.
- 6. Mud Coating
The blade is evenly coated with mud to ensure good quenching.
- 7. Quenching and Tempering
Quenching is an important task that determines the hardness of the blade. After heating the blade in the hardening furnace at 770 to 800°C, it is quenched and hardened by quickly plunging into water.
A hard blade is brittle and will snap; the next process, tempering, imparts durability and toughness to the metal. In a low-temperature tempering furnace at about 170°C and using heated fuel oil, time is taken to slowly bring the blade to heat. It is then removed and allowed to naturally cool.
- 8. Removing Distortion
Any distortion resulting from the quenching and tempering is removed by painstaking hammering of the face and back of the blade.
- 9. Blade Edging and Finishing
Finally, the blade is ground to a sharp edge. It is carefully taken from rough and semi-finish down to fine-grinding.
Generally in the blade-making industry, division of labor is becoming more common; in contrast, Tosa Uchihamono are made by one artisan following a time-honored process, resulting in a greater appreciation of an article made by an artisan using traditional skills.