Tang Design and Finishing: The Meaning of Nakago Shape, Length, and Patina in Japanese Swords

What is Nakago —— The Structure of the Blade's "Root"

The Japanese blade is broadly divided into the "cutting edge section (haba)" and the "nakago". While the cutting edge section is the part that has the actual cutting function, the nakago is housed within the handle (tsuka) and serves as the "root" that fixes the blade to the handle. The boundary line between the cutting edge and the nakago is called the "machi", with the hamachi (edge machi) and munemachi (ridge machi) forming this boundary.

Because the nakago is a part not visible from the outside, it tends to be overlooked in appreciation. However, it is actually an extremely important part in evaluating the value of swords and in authenticity appraisal. The condition of the mei (signature), yasuri me (file marks), and mekugi ana (peg holes) engraved on the nakago, as well as the quality of the rust attached to the nakago, become key clues for understanding the provenance, manufacturing era, and authenticity of the sword.

The design of the nakago is also important in terms of function. The method of fixing within the handle, balance, and grip comfort are all dependent on the shape and length of the nakago, and the sword maker designs the nakago after calculating these factors.

Nakago Shape Types —— Classification as Told by Sword Makers

The shapes of the nakago are broadly classified as follows.

• hagari kuriji: A shape where the tip of the nakago (nakago-jiri) is cut diagonally toward the direction of the blade. Often seen in tachi from the Kamakura period, it is considered the typical style of old swords.
• kuriji: A shape with a rounded tip on the nakago. Common in tachi from the Heian and Kamakura periods, it gives an elegant and old-fashioned impression.
• kiri: A shape where the tip of the nakago is cut at a right angle. Commonly seen in uchigatana, it became popular during the Edo period's shintou (new sword) era.
• kengata: A shape where the tip of the nakago is pointed like a sword. Seen in certain forms of tachi.
• asano kogata: A shape with a gentle curve at the tip.
• kaku: A shape with an angular tip, more common in relatively recent periods.

These shapes are not merely aesthetic preferences, but carry important information indicating the era, school, and habits of the sword maker. In appraisal, the technique of "determining the era from the shape of the nakago-jiri" has been established.

Nakago Length and Functional Design

The length of the nakago is directly related to the intended use of the sword. As a basic rule, the length of the nakago is standardized at approximately one-third of the cutting edge length (blade length). For an uchigatana with a blade length of two shaku and three sun (approximately 70 centimeters), the nakago would typically be around seven sun.

However, the length of the nakago varies by era. Tachi from the Kamakura period have relatively long nakago, and by making the handle long, they increased the stability of two-handed operation. On the other hand, uchigatana from the Edo period tend to have somewhat shorter nakago for the same blade length. This reflects the decreased need for practical combat in a peaceful era and changes in the aesthetic form of the sword fittings (koshirae).

The width of the nakago (nakago-width) is also an important design element. How much narrower the nakago-width becomes compared to the width of the blade root (hamoto) is called the "nakago-sage" (nakago taper). Tachi typically show a form that narrows significantly, while uchigatana often maintain relatively uniform width. Because this change also affects the appearance of the blade after the machi, sword makers pay careful attention to the design of the nakago-width.

Yasuri Me —— The Sword Maker's "Seal"

The yasuri me (file marks) applied to the surface of the nakago carries not merely anti-slip processing but important information identifying the school, sword maker, and era. The types of yasuri me include the following.

• keshou yasuri: Fine and uniform file marks, emphasizing aesthetic beauty. Often seen in high-quality swords.
• kiri yasuri: A form where the file marks run perpendicular (horizontally) to the nakago. Common in tachi from the Kamakura and Nanboku-cho periods.
• suji-kai yasuri: A form where the file marks run diagonally. Particularly common in uchigatana from the Edo period. Multiple schools used diagonal yasuri at specific angles as a "proof of their school."
• osuji-kai: Diagonal yasuri with a steeper angle.
• baikka yasuri: A special type of file marks forming curves like plum blossoms. Used in high-quality swords and ceremonial swords.

The application method of yasuri me is a technique passed down from generation to generation of masters to apprentices through oral tradition. It expresses the characteristics of a school, and the habitual application patterns of a particular sword maker become clues in authenticity appraisal. If the works are by the same sword maker, there is a certain consistency in the yasuri me pattern, making it one of the first parts that experts check in authenticity appraisal.

Reading Rust —— The Witness of the Era

The rust attached to the nakago is the "witness of the era" that tells of the age and history of the sword. A nakago with quality rust attached is said to have "rust that sits," which indicates that the sword has naturally formed an oxide coating over a long time. Generally, it is evaluated as follows.

• furu sabi (old rust): Black-tinged, uniform and dense rust that is evidence of several centuries of natural oxidation. Fine irregularities spread uniformly, appearing to the untrained eye as almost a single black color. Commonly seen in old swords (koutou) from the Kamakura and Muromachi periods.
• aka sabi (red rust): Rust with a reddish hue, indicating that the oxidation of iron has progressed. Generally not valued as highly as old rust, but when specific types of jigane such as sand-iron-based tamahagane are used, characteristic rust colors may appear.
• shin sabi (new rust): Relatively shallow rust, seen in swords from relatively recent eras or swords that have been polished or maintained in modern times.

There also exist methods for artificially creating rust, called "nise sabi" (false rust), a malicious counterfeiting technique that gives ancient coloring to newly made swords to make them appear as old swords. Professional appraisers possess the skill to distinguish between natural rust and artificial rust by examining the uniformity, depth, and attachment pattern of the rust.

The Philosophy That Sword Makers Put Into Nakago Design

For modern sword makers, the design of the nakago is not merely a technical process but an important step representing the "completion" of the entire sword. The shape of the nakago, the yasuri me, the position of the mekugi ana (peg hole), the style of the mei signature—all of these function as the sword maker's "signature."

In particular, the act of engraving a mei is how the sword maker demonstrates their skill and pride to the future, and is also a declaration of "I made this sword." For this reason, the handling of the chisel (tagane) when engraving the mei must be careful and powerful, and the style of the characters, their size, and position have traditional conventions for each school and each sword maker.

The design and finishing of the nakago are done after the main processes of sword-making are complete—striking the blade, tempering, and polishing. In a sense, it is the final finishing of the sword, and it also has a ritual meaning: the sword maker declares "completion" while taking responsibility for their work. In this respect, the nakago is a special part where the technical completion of the Japanese sword as a craft and the sword maker's spiritual commitment intersect.