Measurement Standards for Blade Thickness and Width — How to Measure Motohaba, Sakihaba, and Kasane, and How to Read the Profile by Period

Introduction

The dimensions of a Japanese sword are a shared measure for conveying a sword's profile in numbers. In the product descriptions of sword dealers and the catalogues of exhibitions, values such as nagasa, sori, motohaba, sakihaba, moto-gasane, and saki-gasane appear in rows, but each has a fixed measurement point. This article organizes, with a focus on mihaba (blade width) and kasane (blade thickness), the meaning and measurement points of each dimension, their relationship to registration certificates, and how to read the profile by period from the dimensions.

Names of Dimensions and Where to Measure

• Nagasa (blade length): The length from the mune-machi to the kissaki (point). When indicating the length of the blade, this measurement is used (Touken World, "Nagasa")
• Sori (curvature): The greatest distance from the straight line connecting the kissaki and the mune-machi to the mune (back of the blade)
• Motohaba · sakihaba: The mihaba — that is, the width from the cutting edge to the mune (back of the blade) — measured near the machi and near the yokote respectively
• Moto-gasane · saki-gasane: The kasane — that is, the thickness of the blade — measured near the machi and near the yokote respectively

The definitions of sori, mihaba, and kasane follow Touken World, "Dimensions of the Japanese Sword". Both mihaba and kasane normally decrease from moto (base) toward saki (tip), and the magnitude of the difference between the two affects the visual impression of the sword's profile. The methods and types of sori measurement are also covered in detail in Sori of the Japanese Sword.

An Example of a Standard Uchigatana

Touken World's explanation gives, as an example of standard dimensions for an Edo-period sword, approximately: nagasa 70–73 cm, motohaba 2.9–3.2 cm, sakihaba 2.1–2.2 cm, moto-gasane 0.7–0.75 cm, and saki-gasane 0.5–0.55 cm (Touken World, "Dimensions of the Japanese Sword").

These are merely one reference point. Even among swords of the same period, dimensions vary greatly depending on the maker, school, and intended use. Furthermore, in swords that have undergone suriage (shortening) — in which the nakago (tang) is reduced to shorten the nagasa — the position of the machi shifts upward, so motohaba and moto-gasane are measured at a different point from where they were when the sword was originally made. In swords that have undergone repeated togi (polishing), mihaba and kasane may also have diminished. Dimensions must be read in conjunction with this kind of provenance.

Dimensions Recorded on the Registration Certificate

The firearms and swords registration certificate for a Japanese sword records the type, length, sori, number of mekugi (peg) holes, mei (signature), registration date, and other items (Nagoya Sword Museum, "Registration of Firearms and Swords with the Prefectural Board of Education"). Nagasa (blade length) and sori can be confirmed on the registration certificate, but mihaba and kasane are not among the main items recorded. Mihaba and kasane must be confirmed from the dimensions table in a product description or by measuring the object itself. The reading and procedures for registration certificates are covered in Japanese Sword Registration Certificate Guide.

Basics of Measuring Mihaba and Kasane

• Mihaba is measured as the width from the cutting edge to the mune (back of the blade)
• Kasane is measured near the mune (back of the blade). Because the blade tapers toward the cutting edge, it is important to standardize the measurement position
• Measuring both moto (base) and saki (tip) and recording the difference is useful for comparing profiles
• When measuring, take care not to let the oils or perspiration of your hands contact the blade, and after measuring, apply oil and perform maintenance

Reading the Profile by Period from the Dimensions

Mihaba, kasane, sori, and the size of the kissaki are linked to the characteristic profiles of each period. In the explanations of the Japanese Sword Museum, for example, the following tendencies are noted (Touken World Nagoya, "History of the Japanese Sword by Period", Touken World, "Profile of the Japanese Sword").

• Heian-period tachi: Long, with deep sori and a graceful profile with narrow mihaba
• Mid-Kamakura tachi: Long, with deep sori, wide mihaba, thick kasane, and a practical profile with an ikubi-kissaki
• Late Kamakura through Nanbokuchō: Sori shifts toward the saki (tip), mihaba becomes wide, and kasane becomes thin
• Muromachi-period uchigatana: Wide mihaba, with a medium kissaki and saki-zori profile
• Keichō Shintō: Shallow sori, wide mihaba, and a powerful profile with an elongated kissaki
• Kanbun Shintō: A profile with shallow sori
• Shinshintō (Kansei period): Wide mihaba, thick kasane, and shallow sori

Even with the same mihaba, whether the kasane is thick or thin — and whether the difference between moto and saki is large or small — greatly changes the impression of the sword. When looking at a dimensions table, it is better to picture the profile not from a single value alone but from the combination of moto and saki, mihaba and kasane. Changes in the profile of Edo-period swords are also covered in Morphological Features of Edo Shintō, and differences in length by sword type are covered in Sword Dimensions Guide.

Conclusion

Mihaba and kasane are dimensions directly linked to the strength, weight, and visual impression of a sword. However, it is not possible to determine the maker or period from dimensions alone. By taking into account provenance such as suriage and reduction through togi (polishing), and examining the dimensions together with the profile, jigane (steel of the blade surface), hamon (temper line), and nakago (tang), the numbers begin for the first time to speak to the sword's individual character.