Nakago Tang Finishing Craft — Post-Quench Tang Shaping, Mekugi-ana Drilling, and Yasuri-me Filing Techniques
* Image is for illustrative purposes only.Table of Contents
What is the Nakago—The Technical Significance of the Blade's "Root"
The nakago is the root section of the blade that is inserted into the tsuka (hilt), and functions as an "invisible foundation" in the overall Japanese sword. While connoisseurship and appraisal focus on the hamon, jihada, and overall form, the nakago carries information such as the swordsmith's signature, file marks, and mekugi hole, making it one of the most critical parts for determining a blade's authenticity, period, and school.
From the perspective of forging technique, the nakago is not merely "the part that goes into the hilt" but rather a precision structure that receives careful finishing work after the hardening process. The proper form and finish of the nakago directly determine the fit with the hilt, stability during drawing, and stress distribution to the mekugi, revealing aspects of the swordsmith's skill.
In appraisal settings, the nakago is equally valued alongside the hamon and jihada. The form, file marks, and position and number of mekugi holes serve as clues for estimating period and school. The patina on the nakago's surface results from long-term aging, and its color and texture also inform appraisal judgments. Therefore, direct contact with bare hands is avoided to prevent oils from damaging it, and careful handling is necessary.
The Process of Nakago Finishing Before and After Hardening
During the fire-forging (hidzukuri) stage, which establishes the blade's basic shape, the nakago's exterior profile is essentially determined. At this stage, the position of the ha-machi and the nakago's length, basic width, and thickness are finalized, with the nakago section formed as a rod of iron.
During the clay coating (tsuchi-oki) stage performed before hardening (yaki-ire), the blade receives refractory clay to form the hamon, but the nakago is left without clay, with exposed metal, and placed in the furnace. After hardening, the nakago does not harden from the furnace heat but enters a tempered state with appropriate toughness. This is a design consideration to prevent the nakago from cracking during mekugi hole drilling and assembly/disassembly.
While the blade edge becomes hard and brittle, keeping the nakago in a softer state prevents cracking and chipping during subsequent filing and mekugi hole drilling. If the nakago hardened the same way as the blade edge, cracks would form when drilling the mekugi hole, making it difficult to stably support the blade within the hilt. Therefore, the decision not to apply refractory clay to the nakago during the clay coating stage itself is a critical process that determines the entire subsequent finishing workflow.
Nakago Shaping—Finishing and Tools by Form
After hardening, nakago shaping begins. First, files and a hammer are used to level the nakago's surface and clearly shape the boundary line called the "ha-machi" and "mune-machi." The finish of the machi relates to the overall balance of the sword; if the machi is too sharp, the boundary with the hilt appears visually unnatural, and if too rounded, blade strength decreases. Thus, careful judgment is needed to achieve the proper form.
The nakago's outline has multiple styles, chosen according to period, school, and individual swordsmith characteristics.
- Funazoko-gata (boat-bottom form)
- Kurijiri-gata (chestnut-tail form)
- Ken-gata (sword form)
- Ha-nobori-mune-sagari-gata (rising-edge falling-ridge form)
Ko-to (old swords) from before the Muromachi period typically feature relatively long nakago with rounded forms, while shin-to (new swords) from the Edo period onward tend toward shorter, more parallel shapes.
During shaping, the sides of the nakago (both the mune side and ha side) are carefully leveled so that even minute irregularities conform to the interior shape of the hilt. Since the hilt is inherently hollowed to fit the nakago's shape, rough finishing creates gaps that can cause rattling or damage during use. Conversely, excessive shaping compromises the nakago's strength and weight balance; maintaining sufficient smoothness without over-removal relies on the swordsmith's experience and judgment.
Mekugi Hole Drilling—Precise Management of Position, Diameter, and Angle
The mekugi hole is the opening through which the mekugi pin secures the hilt to the blade, and its position, diameter, and angle determine the fit precision with the hilt. Traditionally, chiseling and hammering were used, and many contemporary swordsmiths maintain this technique.
| Item | Details |
|---|---|
| Position | Determined by the ratio of the nakago's length and width, based on calculations considering center of gravity balance |
| Diameter | Generally 4-6mm, adjusted to match the cross-sectional diameter of the mekugi material (traditionally bamboo) |
| Angle | Often tilted slightly toward the blade rather than perpendicular to the nakago surface, allowing mechanical load during drawing to be distributed across the entire mekugi |
Care must be taken in hole placement as drilling too close to the nakago's edges (near the mune or ha side) concentrates force and creates crack initiation points. Swordsmiths carefully position holes with sufficient margin from the nakago's width. When appreciating or purchasing existing blades, checking for radial cracks extending from the mekugi hole edges is a fundamental inspection point.
When an old blade has multiple mekugi holes, this evidences shortening of the nakago through polishing and restoration (suriage), with the number and position of holes serving as critical appraisal data. New swords typically receive only one mekugi hole, and swordsmiths sometimes position it considering potential future suriage.
File Marking—Inscribing the Swordsmith's "Fingerprint" on the Nakago
The final step in nakago finishing is file marking (yasurime), where various files create regular grooves on the nakago surface. File marking exhibits diverse patterns, with different schools favoring different styles.
- Osuji-kai (large diagonal)
- Kosuji-kai (small diagonal)
- Yoko (horizontal)
- Takano-ha (hawk feathers)
- Higaki (cypress lattice)
File marking serves not merely as decoration but as a practical function for "increasing friction" when inserted into the hilt. Proper file marking increases the contact density between the hilt wood (tsuka-gi) and nakago, preventing hilt loosening during use. Simultaneously, file marking is "the part where the swordsmith's individuality appears most clearly," and comparing works by the same smith often reveals consistent patterns in the file marking technique. This is why file marking style can serve as supplementary appraisal evidence even for swords with unknown signatures.
When a blade undergoes suriage (polishing and shortening), file marks may be re-cut on the shortened nakago, a practice called "re-marking" (yasurime no kakke-nashi). Re-marked file marks may differ subtly in direction and spacing from the original swordsmith's work, and these differences serve as clues for understanding the nakago's history during appraisal. In this way, nakago finishing technique is not mere post-processing but a critical stage that inscribes indispensable information for understanding a blade's authenticity, period, and school.
