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

What is the Nakago (茎)? — The Structure of the Sword's "Root"

The blade of a Japanese sword is broadly divided into the "habú (刃部)" and the "nakago (茎)." While the habú is the functional part that actually cuts, the nakago is embedded within the handle (tsuka) and serves as the "root" that fixes the blade to the hilt. The boundary between the habú and nakago is called the "machi (区)," formed by the hamachi (刃区) and munemachi (棟区).

The nakago is hidden from external view, and thus often overlooked in appreciation, but in fact it is an extremely important part in evaluating the value of Japanese swords and authenticating their genuineness. The condition of the mei (銘) inscribed on the nakago, the yasurímé (鑢目) file marks, and the mekugi ana (目釘穴) nail holes—along with the quality of rust that adheres to the nakago—serve as key clues for interpreting the blade's provenance, manufacturing era, and authenticity.

The design of the nakago is also functionally crucial. The method of fixing within the hilt, balance, and grip comfort are all governed by the shape and length of the nakago, and the swordsmith designs it with these factors carefully calculated.

Nakago Shape Classifications — Nine Categories That Swordsmiths Recognize

Nakago shapes are broadly classified as follows:

Hagari Kurijiri (刃上がり栗尻): The tip of the nakago (nakago jiri) is cut diagonally toward the edge side. Common in tachi from the Kamakura period, this is considered the typical style of old swords.

Kurijiri (栗尻): The tip of the nakago has a rounded form. Frequently seen in tachi from the Heian and Kamakura periods, it conveys an elegant and antique impression.

Kiri (切): The tip of the nakago is cut at a right angle. Often found on uchigata na (打刀), this became widespread during the shintos (new swords) era of the Edo period.

Kengas (剣形): The tip of the nakago is pointed like a sword. Seen in certain styles of tachi.

Asa no Kogata (浅の子形): The tip describes a gentle curve.

Kaku (角): The tip is angular, more common in relatively recent periods.

These shapes are not merely aesthetic preferences but carry important information about era, school, and the swordsmith's habits. In authentication, an established technique—"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 nakago length is typically standardized at approximately one-third of the blade length (toshinchō). For an uchigata na with a blade length of 2 shaku 3 sun (approximately 70 centimeters), the nakago would average around 7 sun.

However, nakago length varies by era. Tachi from the Kamakura period have relatively long nakago, with the longer hilt designed to enhance stability in two-handed operation. Uchigata na from the Edo period tend to have slightly shorter nakago for the same blade length, reflecting the decreased need for practical combat capability in a peaceful era and changes in koshirae (sword furnishings) aesthetic form.

The width of the nakago (nakago width) is also an important design element. How much narrower the nakago width is compared to the width at the ha moto (blade root) is called the "sagari kata (下がり方)," and tachi typically exhibit a "large descent" where it narrows significantly, while uchigata na usually maintain relatively uniform width. Since this change affects the external appearance of the blade below the machi, swordsmiths exercise meticulous care in designing the nakago width.

Yasurímé (鑢目) — The Swordsmith's "Seal"

The yasurímé file marks on the nakago surface are far more than mere anti-slip finishing; they carry crucial information for identifying school, swordsmith, and era. Types of yasurímé include the following:

Keshō Yasuri (化粧鑢): Fine, uniform file marks emphasizing aesthetic beauty. Often found on high-quality swords.

Kiri Yasuri (切鑢): File marks run perpendicular (horizontally) across the nakago. Common in tachi from the Kamakura and Nanboku-chō periods.

Sujikai Yasuri (筋違鑢): File marks run diagonally. Particularly prevalent in uchigata na from the Edo period, with multiple schools using specific angles of sujikai yasuri as a "school signature."

Ō Sujikai (大筋違): A steeper angle version of sujikai yasuri.

Baika Yasuri (梅花鑢): A special file mark pattern describing curves like plum blossoms. Used on high-quality swords and ceremonial blades.

The application of yasurímé is a technique transmitted orally from master to apprentice across generations, representing the character of a school while the swordsmith's habitual patterns of execution serve as authentication clues. In works by the same swordsmith, yasurímé patterns show consistency, making it one of the first areas specialists examine during authentication.

Reading Rust (さび) — Testimony of Time

The rust adhering to the nakago is the "testimony of time" that speaks to the blade's age and history. A nakago with high-quality rust is described as "rust sitting well," indicating the blade has naturally formed an oxide coating over extended time. Generally evaluated as follows:

Furusabi (古錆): Dark, uniform, and finely granular rust—testimony to centuries of natural oxidation. Fine, uniform surface irregularities create an appearance of nearly solid black to the untrained eye. Frequently seen on old swords from the Kamakura and Muromachi periods.

Shusabi (朱錆): Reddish-toned rust, indicating advanced iron oxidation. Generally rated lower than furusabi, though certain specific iron compositions (sand iron-based tamahagane, etc.) can produce distinctive rust coloration.

Shinsabi (新錆): Relatively shallow rust seen on swords from more recent eras or those that underwent polishing and maintenance in modern times.

Techniques for artificially applying rust—"false rust" (nisesabi)—exist as a malicious falsification method to apply antique patina to newly made swords. Professional appraisers possess the skill to distinguish natural rust from artificially applied rust by examining uniformity, depth, and adhesion patterns.

Philosophy Embedded in the Swordsmith's Nakago Design

For contemporary swordsmiths, designing the nakago is not merely a technical procedure but a significant step that represents the "completion" of the entire sword. The shape of the nakago, the yasurímé, the position of the mekugi ana, the calligraphy of the mei—all function as the swordsmith's "signature."

In particular, the act of inscribing the mei is the swordsmith's declaration to the future of their own skill and pride—a statement saying "I made this sword." For this reason, the movement of the chisel (tagane) when inscribing the mei must be deliberate and forceful, with each school and swordsmith following traditional conventions in the style of characters, character size, and placement.

The design and finishing of the nakago occurs after the major processes of sword manufacture—forging the blade, heat-treating, and polishing—are complete. In a sense, it is the final finishing of the sword, with ritualistic significance as the swordsmith takes responsibility for their work and formally declares its "completion." In this respect, the nakago is a special site where the technical completion of the Japanese sword as a craft object intersects with the swordsmith's spiritual commitment.