- by Lin
- March 14, 2024
- Katana info
- Comments:2
The Katana Blade
The ‘sori’ or curvature of the katana blade is determined by the clay tempering process, and the blade is not made to be purely hard. The ‘sori’ can increase impact resistance.
The katana’s main action is ‘cutting’. When performing a cutting motion, a ‘pulling’ action is needed rather than striking down hard like a European sword. Of course, you can take the sword and hack at an opponent, but hacking is less efficient.
In other words, the katana blade flows along an arc (part of the circumference). By adding curvature to match the arc, the ‘pulling’ action becomes smoother. Beyond this cutting action, the katana’s characteristic sharpness gives it great striking power. And makes it feel lighter than its actual weight.
One benefit of the curve is that the blade enters the target at an angle, allowing it to better leverage its force (with less effort).
Also, with the center of mass closer to the hilt, the blade feels lighter and is considered better suited for quick drawing and combat compared to a ‘non-curved’ Japanese sword.
Bo-hi Grooves
The bo-hi are elongated grooves carved near the shinogi ridge of the blade. Their function is often misunderstood as being for bloodletting.
In fact, the bo-hi are designed to reduce the weight of the blade without compromising performance too much. To reduce weight, other parts of the blade cannot be modified, so the only option is to remove material from the ji or ridge area. This way, the overall blade shape is unaffected but weight is reduced. Bloodletting is just a side effect, not the purpose.
By absorbing forces parallel to the edge, the bo-hi also make the blade less prone to bending. So they serve the dual purposes of reducing weight while maintaining blade integrity.
The Hamon Temper Pattern
The hamon is the distinct wavy temper pattern between the blade edge and back, you can see glittering grains that look like scattered stars. that makes Japanese swords famous. Though decorative today, it originally made the edge harder.
During quenching, clay is coated on the edge so it cools milliseconds faster than the back. This difference in cooling rate hardens the edge yet allows flexibility at the spine. While once functional, the hamon now displays artistic mastery.
Creating it involves more than just clay. The smith must expertly judge steel, temperature, clay mixture, and proper blade heating before the tense moment of quenching, where steel transforms violently to forge the ideal hamon.
Though just a “temper line”, the hamon remains prominent worldwide as a symbol of Japanese swordmaking skill that balances art, science, and function at the edge of beauty and destruction.
The Kashira Handle End
The kashira is a sword fitting installed at the end of the handle. In Japanese fitting swords,The kashira was originally added to sword hilts to increase strength in early sword design. As the peaceful Edo period arrived, society stabilized and commerce thrived. The katana at this time emphasized the elegance of fittings more. And the “kashira” gradually shifted towards a decorative role.
The kashira process is not simple. First, the general shape can be carved out of copper. Then the main pattern is carved and inlaid with gold and silver dots before being treated with a darkening process. Finally, the main pattern is colored using the gilding technique . A well-formed kashira with standardized dimensions is a sign of good handle accessories.
The Sageo Cord
The sageo is a braided cord made of silk or cotton, about 180-240cm long, tied to the side of Kurigata. In the past, its main functions were to prevent the sword from being stolen and to keep the katana’s position and scabbard angle fixed during running or vigorous motion, which could otherwise hinder movement.
When a katana was placed on a rack for long-term storage, the sageo would be tied in a knot. The specific knot types and tying methods changed over time. For convenience, Now katana sageo are tied in a “ronin knot”. This decorative, non-functional knot is said to be named as such because “a ronin would have no use for a katana, so practicality is ignored and a visually pleasing knot can be used instead.”
The Seppa Spacer
The Seppa is a thin piece of metal fitted between the blade and the tsuba. Its material is usually corrosion-resistant and workable metals like copper. More precious metals like gold or gilded iron may be used on high-end swords.
The main purpose of the Seppa is to prevent the tsuba from shifting. Other proposed functions are fixing the blade during slashing, cushioning impact to the hand, and adjusting the grip.
As a thin metal sheet, the kawazuko is prone to wearing down with use, second only to the mekugi. It can deform when changing tsuba or sheathing the blade. Traces of contact with the habaki are often visible on well-used Seppa.
Mekugi Pegs
Wooden pegs (mekugi) fix the blade’s tang to the handle, ensuring a tight fit along the entirety of the hadnle. A katana handle typically has two mekugi pegs.
Some swords with metal fixtures on the front and back need just a single middle mekugi to hold the blade firmly. Using one mekugi improves shock absorption, balancing forces from blade to handle This grants the wielder better control and less fatigue.
So while two pegs are standard, a single wooden mekugi can be advantageous by acting as a cushion. Though simple, the mekugi plays a vital role in katana construction and function.
The Tsuba Handguard
Tsuba (つば, Tsuba) refers to the guard on Japanese swords, typically a round or square protector located at the junction of the handle and the blade. Its purpose is to prevent direct contact between the enemy’s blade and the hand of the samurai, while also providing balance in sword techniques.
In the art of swordsmithing, (つば, Tsuba), known as the “soul” of Japanese sword fittings, is a unique art form that leads Japan’s sword and blade culture ahead of other countries. Some say that if the entire set of sword fittings represents a samurai’s attire, then the tsuba can be considered the samurai’s face.
Before the Azuchi-Momoyama period, Tsuba designs prioritized functionality to meet the demands of combat. However, as time progressed, particularly during the Edo period, the growth of peaceful times led to a transformation in the role of samurai, and swords evolved from practical weapons into symbolic items representing status and aesthetic taste. Consequently, the design and craftsmanship of Tsuba gradually emphasized decoration, becoming a unique form of art that showcases the skill and creativity of artisans.
Tsuba, the hand guard on Japanese swords, comes in various shapes like round, square, or irregular. The design is often ornate with intricate patterns or images depicting nature, animals, or mythological beings. The size ranges from small and slim to large and robust depending on the period.
Materials: Tsuba are made from a variety of materials including iron, copper alloys, precious metals like gold and silver, as well as ivory, horns, wood, and lacquer. Different materials lend unique properties and aesthetic qualities.
Functionality: The primary function of tsuba is to protect the hand from opponent’s blades. It also balances the sword, absorbs shocks, and can entangle or deflect the enemy’s sword. Robust tsuba were favored in wartime while decorative tsuba became popular during peaceful Edo era.
Value and Collecting: Fine tsuba are highly valued as art objects. Rarity, age, materials, aesthetics, and artistry determine the value. Tsuba collecting was popular among aristocrats and high-ranking samurai as a symbol of status. Today, tsuba remain sought-after antique collectibles.
Menuki Handle Ornaments
Menukis are small metal pieces installed at the center of both sides of the handle, usually made of brass. The katana handle has holes piercing both sides, and to prevent the blade from slipping out, a piece called a “mekugi”( wooden pegs) is inserted into the holes. It originally existed as the head of the mekugi peg.
Later, the Mekugi and Mekuki separated, and the mekugi peg became a functional piece emphasizing utility. Although the mekuki became more decorative, when woven under the handle wrapping, it can play an important role in adjusting the grip to be better.
The mekuki has two functions. One is to increase the friction of the handle. The other is to give the overall equipment design a unified and coordinated aesthetic. The fittings of a Katana are not just copies of the same pattern simply repeated, but often present a continuous pictorial rhythm, which is incredibly beautiful.
The Habaki Blade Collar
The habaki is a metal fitting installed where the blade meets the tsuba guard. Originally iron, habaki evolved to softer, anti-rust metals like copper.
The habaki serves two main purposes:
- Keeping the blade suspended and centered when sheathed, minimizing contact with the wooden scabbard interior to avoid scratches and rust.
- Securely holding the blade in the scabbard while allowing quick, smooth drawing. A light grip releases the blade instead of the dangerous slipping that could occur.
Quality habaki have crisp, straight edges and snugly fit the blade without rattling. Their shape is plug-like, tapering front to back, with a curved surface ensuring good contact with the koiguchi scabbard mouth. Both functionally and aesthetically, the habaki is an ingenious sword fitting.