The System of Smithing Tools: How Hammers, Anvils, Bellows, and Quenching Water Define the Swordsmith's Craft

Tools Define Technique—The Significance of Blacksmith Tool Theory

There is a saying that "the master chooses no brush," but in Japanese sword forging, "the bladesmith chooses their tools." The finest bladesmiths hold strong preferences for their tools, treating tool selection, adjustment, and fabrication as part of their technique.

The Japanese sword forging process—heating tamahagane, forging, shaping, and quenching—requires specialized tools at each stage. These tools are not mere "equipment"; they form a precise tool system that embodies the bladesmith's technical philosophy.

Tsuchi (Hammer)—The Star That Shapes Steel

Ōtsuchi (Large Hammer)—Building the Framework

The ōtsuchi is a heavy hammer used in the initial stages of forging. It plays the central role in tempering and folding tamahagane, and creating the rough form (subase) of the blade.

Weight: An ōtsuchi typically weighs 2 to 5 kg. Preferred weight varies depending on the bladesmith's physique and forging style.

Materials: The head is typically made of steel, while the handle is made of wood (ho or chestnut, etc.). The balance between the hardness of the steel head and the hardness of the kanajoko (anvil) is important; too hard a hammer damages the steel, while too soft reduces efficiency.

Role of the senior apprentice (sakideshi): In traditional forges, a hierarchical division of labor occurs: the master (bladesmith) sets the rhythm with a small hammer while an apprentice (senior apprentice) swings the ōtsuchi. The master's small hammer shows "where to strike," and the apprentice's ōtsuchi applies force at that location. This "breath alignment" affects both the efficiency and quality of folding and tempering.

Kotsuchi (Small Hammer)—Precision Shaping Tool

After rough shaping with the ōtsuchi, precision shaping is done with the kotsuchi. The bladesmith holds it directly in hand to refine details.

Weight: Typically 500g to 1.5 kg.

Shape Diversity: The kotsuchi varies in shape depending on purpose. The "hiratsuchi" (flat hammer) with a flat surface, "kakutsuchi" (square hammer) with corners, "marutsuchi" (round hammer) with a curved surface, etc. Different hammers are used depending on shaping each section of the blade (kissaki, shinogi, and hilt area).

Kitsuchi (Wood Hammer)—Collaboration with Saya-shi and Tsuka-shi

The wooden hammer is used to adjust shape without directly striking metal. It is also used when the tsuka wrapping specialist applies ray skin (same) and when the polisher applies whetstones.

Kanajoko (Anvil)—The Foundation That Receives Steel

Functions of the Anvil

The kanajoko is the bench that receives the steel struck by the hammer. Throughout the entire forging process, steel is worked on top of the kanajoko.

Material: The kanajoko is generally made of steel, but the hardness of its surface (degree of quenching) is important. If too hard, the steel is easily damaged; if too soft, the kanajoko itself deforms.

Weight and Stability: The heavier the kanajoko, the more stable it is. A light kanajoko moves with hammer impacts, making precision shaping difficult. Large forges sometimes use anvils weighing over 100 kg.

Anvil Shapes

Flat Type (heimengatа): The most basic shape. A wide flat surface supports the steel.

Horn Type: A shape with "horns" (projections) on one or both sides. Bending and fine shaping can be done on the horns. Used for kissaki curve forming, etc.

Groove Type (mizogata): An anvil with grooves carved into its surface. When shaping round rod-like materials, the groove stabilizes the material.

Fuigo (Bellows)—The Tool That Commands Flame

Function and Principle of the Bellows

The fuigo is a ventilation device that pumps air (oxygen) into the forge. To heat iron to the appropriate working temperature (800–1200°C), forced ventilation of fuel (primarily charcoal) is necessary.

Traditional fuigo is called the "hakofuigo" (box bellows)—a wooden box-shaped ventilation device. Inside the box is a piston-like plate (fuigoita), which is moved back and forth to push air out.

Air Volume Management—The True Nature of "Fire Adjustment"

The volume of air pumped into the forge directly controls the heating temperature of the steel. More air (strong ventilation) raises the temperature; less air (weak ventilation) lowers it. The bladesmith adjusts this air volume by controlling the speed of the fuigo, observing the color of the steel (red-heat, yellow-heat, white-heat differences) to judge the appropriate temperature.

"Observing the fire adjustment" is actually a complex management involving both fuigo operation (air volume) and forge fuel placement (amount and arrangement of charcoal).

Modern Bellows

In modern forges, electric blowers (blower fans) are widespread. They make it easier to stabilize air volume compared to hand-operated box bellows and reduce apprentice physical fatigue. However, some bladesmiths maintain traditional box bellows because "electric blowers cannot perform the subtle adjustments of hand bellows."

Yakimizu (Quenching Water)—The Life Water of Quenching

The Role of Quenching Water in Quenching

"Quenching (yakiire)" is the most critical process in Japanese sword making, creating the hamon. When the white-hot blade is rapidly cooled in water (yakimizu), the high-carbon edge section undergoes martensitic transformation, producing a hard edge.

The water used for this rapid cooling is "yakimizu." The water quality, temperature, and container (water tank) material of the yakimizu significantly affect the results of quenching (hamon shape, cutting ability, degree of curvature).

Water Quality—The "Individuality of Water" That Bladesmiths Value

It is said that "soft water" is suitable for Japanese sword quenching. Hard water (water with high mineral content) may affect rapid cooling efficiency.

Historical records show that tōkō from famous sword regions (Bizen, Soshu, Yamashiro, etc.) valued the "quality of water." The famous record of Bizen (Okayama) tōkō valuing "Asahi River water" is well-known. Many modern bladesmiths also attach importance to local water, well water, or specific spring water.

Water Temperature—Management by Season and Time

The temperature of yakimizu is generally considered to be around "body temperature (approximately 35–40°C)," though this varies by bladesmith.

Since water temperature changes between winter and summer, heating or cooling may be used to adjust water temperature by season. "Quenching is difficult in winter" because when the water temperature is too low, the rapid cooling efficiency changes and the risk of cracks (yakiwarre) increases.

Water Tank Material (mizuoke)

The container for yakimizu also reflects the preferences of each bladesmith. A wooden tub (oke) is traditional, but wood has the property of gradually maintaining water temperature. Today, metal and plastic water tanks are also used, but some bladesmiths insist, "It must be a wooden tub."

Kajiba (Forge)—Space That Activates Tools

Furnace Placement and Direction

The position of the furnace (combustion device) is the core of forge design. During forging, the positions of the three points—furnace, kanajoko, and yakimizu tank—are designed so the bladesmith can work most efficiently.

The direction of the furnace (flame direction) and light (natural light) are also important. The bladesmith observes the color (temperature) of the steel visually, so a forge with appropriate natural and flame light is essential.

Temperature and Humidity Management

The forge's temperature and humidity also affect forging. Especially in the quenching process, surrounding temperature affects yakimizu temperature, so work planning must account for the season. This is why many bladesmiths have the custom of concentrating quenching work in winter.

Conclusion—Tools Are the Bladesmith's "Second Hands"

Japanese sword forging is a place where the bladesmith's "eyes," "ears," "hands," and "intuition" work at full power. However, for those senses to function, the tools supporting them must be precisely set up.

An appropriately weighted tsuchi, precisely level kanajoko, fuigo capable of subtle air volume adjustment, yakimizu with optimal water quality and temperature—only when all these are in place does the bladesmith's technique become manifest in the blade.

To know tools is to know the bladesmith's work. The tsuchi and kanajoko arranged in the forge are not merely lumps of metal; they are the material foundation of a precise technical system that produces Japanese swords as works of art.