Tosa forged blades

Tosa uchihamono is a Kochi metalwork blade family rooted in the old Tosa region. Production is described across eastern and central Kochi, including Kami, Nankoku, Tosa, Ino, and Susaki, with wider manufacturing areas also named in Kochi City, Aki, Tosashimizu, and nearby places. The geography matters because the blades developed as working objects across multiple blacksmithing communities.

The forest and farm landscape gives the blades their concrete range. Sickles, nata, axes, saws, and hoes belong to agricultural and forestry work; kitchen knives belong to cooking work. Each form carries a task: clearing grass, cutting branches, shaping wood, turning soil, or preparing food. When people call this a local tradition, the word points to those named tools, those landscapes, and the hands that use them.

The central method is jiyu tanzo, or free forging. Smiths heat iron, carbon steel, or both, then hammer the metal longer and wider without relying on a fixed die. Dimensions and handle angles can be adjusted for use, place, soil, and body height. A hoe can take a San'in-style or Tosa-style form; a sickle can change between a shorter plains version and a mountain version with a longer handle and stronger angle.

This method makes design a matter of the body. The back and waist of a blade can be left thicker while the edge is made thin, changing how the tool feels during long work. The practical boundary of quality is visible in the blade back, edge, handle angle, and weight balance, where a tool meets a field, a tree, or a hand.

The material boundary is direct: the blade body uses iron, carbon steel, or a combination of the two, while handles are made of wood. In one core step, the smith prepares the steel for the cutting edge, opens a split in the iron, inserts the steel, taps it in, and heats the piece for forge welding so iron and steel become one body.

Different tools then receive different treatments. Sickles, kitchen knives, nata, and handled sickles are coated with mud before quenching and rapid cooling. Axes and tobi require their own socket work, and saws are shaped from one piece for the body, neck, and tang. These tool names mark differences in material handling, joints, edge lines, and use.

The process starts before the metal enters the fire. Charcoal is cut to a suitable size so the bellows can help control the heat. From there, the work moves through steel and iron preparation, splitting, forge welding, forging, shaping, and rough grinding. Belt hammers may assist in shaping, while hand hammering remains part of the adjustment.

Before quenching, mud is applied to certain blades. The metal is heated to about 770-800°C and then rapidly cooled; tempering follows at about 170°C so the edge can hold hardness while withstanding use. Straightening, edge setting, sharpening, and finishing are completed by hand, which means the final line and edge angle are still settled through the smith’s touch.

A 1590 land survey of Tosa lists 399 blacksmith households, giving the old blacksmithing community a tangible scale. In 1621, the Tosa domain’s Genna reforms promoted forest-resource management and new-field development, increasing demand for agricultural and forestry blades. The growth of Tosa uchihamono is tied to those working needs.

The history is easier to see as a route of labor: forests required cutting and branch work, fields required clearing and digging, and blacksmiths turned fire, iron, and steel into sickles, nata, axes, saws, and hoes. Continuity here means repeated work around tools, land, and trained hands.

The present chapter includes an aging workforce and a shortage of successors. Kajiya Soseijuku opened in Kami in 2019 with three first trainees, and active smiths teach classes in forging, materials, and business.

The school places continuity inside daily training. New smiths learn charcoal fire, steel, hammering, edge setting, tool use, and workshop operation. Because cooks, forestry workers, and farmers use kitchen knives, nata, handled sickles, axes, tobi, hoes, sickles, and saws, the next generation must understand who holds each blade and what work waits for it.