Tools and Workshop Layout of a Swordsmith: From Forging Hammers and Whetstones to the Modern Kaji-ba

Basic Structure of a Forge (Tantojo)

A modern swordsmith's forge (tantojo) is a dedicated facility that inherits the tradition of the ancient smithy (kajiba) while meeting contemporary standards for construction, fire prevention, and occupational safety. A typical forge is about 30 to 60 square meters in size and is equipped with a furnace (bellows-fired or electric), an anvil (kinudai), a water tank, tool racks, and ventilation systems. The roof is tiled or metal-sheeted, and a smoke duct (endo) for exhausting smoke is installed above the furnace.

The heart of the forge is the fire bed (hidoko). A traditional fire bed is a recessed pit furnace that uses coke or charcoal as fuel. Most modern smiths use coke, but some smiths insist on using charcoal. A bellows (fuigo) is used to supply air to the furnace. A traditional box bellows had a structure where air was pumped in by stepping on boards on both sides, but nowadays electric blowers are often used in combination. Furnace temperature control is a skilled technique of the swordsmith, who adjusts the heating degree by visually judging the color of the steel (red-heat, yellow-heat, white-heat).

Types and Uses of Smithing Hammers (Kajitsugi)

Smiths use multiple types of hammers (hamma), each applied to different stages of the process. The main types are as follows:

Large Hammer (Ootsuchi): A large hammer weighing approximately 1–3 kg, wielded by an apprentice called the "striker" (utte). It is used in the early stages of forging to roughly expand the steel by striking. The handle is about 1 meter long, allowing a powerful strike with the full weight of the body.

Hand Hammer (Tetsugi): A medium hammer weighing about 600g to 1kg that the smith holds in one hand. It is used in the finishing stages of forging and for fine adjustments of form. The head is made of steel, and the striking surface is chosen based on its curvature—"flat striking" or "curved striking," etc.

Small Hammer (Kotsuchi): A small hammer weighing about 200–400g, used for detailed shaping and finishing the spine (mune) and ridge (shinogi). The handling of the small hammer is where the smith's individuality is most evident, and the manner in which hammer marks (tsuchime) are left affects the character of the blade.

The anvil (kinuta) is a steel platform that serves as the base during forging. There are flat anvils (hirakinuta) and grooved anvils (katakinuta). The grooved anvil has grooves (katagroove) for shaping the cross-sectional form of the blade and is used in the "shaping" (tsukurikomi) process.

Quenching Equipment—Water Tank, Clay Pot, and Spatula (Hera)

The quenching (yakiire) process requires specialized equipment. The water tank for quenching is called a "quenching tub" (yakibune), which was traditionally made of wood or ceramic, but is now usually made of stainless steel. Since water temperature control directly affects the success of the quenching, many smiths keep a thermometer on hand and adjust the water volume and temperature by season. The shape of the water tank is adjusted to the length of the blade (hacho), with a standard size of 80–100cm to accommodate a typical blade (katana) of 65–75cm.

Equipment for mixing and storing "clay coating" (tsuchitori)—a fireproof clay applied to the blade before quenching—is also an essential item in the forge. The clay for coating is made by combining clay, charcoal powder, whetstone powder, and other materials, and spatulas (hera) and brushes (hake) are prepared for application. The material and shape of the spatula vary by smith, and many smiths make their own. Since the thickness of the clay coating and how the boundary line is drawn determine the design of the hamon, the precision of the tools used in this process is extremely important.

Grinding and Finishing Equipment—Files, Whetstones, Rough Polishing

At the "finishing forging" stage, where the blade is shaped after forging, files (yasuri) are an indispensable tool. Iron files come in coarse, medium, and fine grades, used to adjust the angles of the ridge area (shinogiji), flat area (hiraji), and spine. Modern smiths sometimes use electric grinders as a secondary tool, but the final surface finish of the blade is entirely by hand.

"Rough polishing" (meaarashi) is the coarse grinding done by the smith before handing the blade to the polisher (togishi), using coarse whetstones (aratogu) of low grit. At this stage, any warping of the blade is corrected and the straightness of the ridge and the angle of the edge are brought within acceptable range. Rough polishing sometimes involves difficult judgment, and this is a process that tests the smith's experience and sense. The "tool rest" (zaganedai) in the smithy is a wooden or metal platform used to hold the blade during polishing, used by the smith when applying the final polish.

The Modern Swordsmith's Studio—Auxiliary Equipment and Safety Management

In modern forges, various auxiliary equipment has been introduced in addition to traditional tools. Electric blowers, thermometers (for furnace temperature and water temperature), exhaust fans, and sound-dampening materials are cited as standard equipment. In addition, when applying for permission to forge with the Agency for Cultural Affairs, the installation of fire prevention equipment (fire extinguishers, fire shutters, etc.) is mandated, and rigorous safety management is required.

The lighting in the smithy also requires careful consideration: during the day, natural light is used; at night, fluorescent lights are the standard; but during quenching, many smiths intentionally darken the space to nearly that of a darkroom to more accurately perceive the color development (color temperature) of the steel. Most modern smiths operate in a small-scale setup as independent masters with one or two apprentices. The forge transcends being a mere workshop and serves as a dojo-like space where master and apprentice transmit technique and spirit to one another. Even in the care, arrangement, and storage of tools, the smith's attention to detail and philosophy are reflected, and the workshop itself can be said to be a "self-portrait of the swordsmith."