Can a Broken Nihontō Be Repaired? — The Restorability of Edge Chips, Rust, and Sai-ba, with an Approximate Guide to Costs

Damage to Nihontō — The Choice Every Owner Faces: Restore or Preserve

A nihontō is an extremely delicate work of art made from an intricate alloy of iron and carbon. The longer its history, the more various forms of damage accumulate on the blade. Damage takes many forms: chips, fractures, and bends from combat; rust from age; corrosion from poor storage conditions. For kotō made before the Edo period in particular, it is unavoidable that centuries of time leave their mark on the blade. The question is how to address that damage. The choice between restoration and preservation is one of the most important decisions an owner must make, as it greatly affects both the academic and market value of the sword.

Repairing Edge Chips — The Scope and Limits of Togi

Chips and nicks that form on the cutting edge of a blade are called edge chips (ha-kobore). Small edge chips can be repaired through togi by a togishi. A togishi possesses the advanced skill to dress the chipped area while maintaining the shape of the blade. However, repairing large edge chips or deep nicks inevitably requires significantly altering the original shape of the blade.

When considering the repair of edge chips, it is essential to first have an experienced togishi assess the blade and understand in advance how its shape, kasane, and hamon will change as a result of the repair. In some cases, the hamon may be partially lost through the repair process. A togishi may advise that "not repairing preserves more value," and it is wise to respect that judgment.

The Problem of Rust — The Critical Difference Between Surface Rust and Pitting Rust

Rust is the most frequently encountered challenge in sword care. Rust has two distinct stages.

• Surface rust (floating rust): Thin red rust adhering to the surface of the blade. It can be removed by careful togi by a togishi, and if addressed early it is possible to restore the beauty of the hamon and jigane almost completely.
• Pitting rust (mushikui-sabi): Rust that has progressed deep into the interior of the blade through neglect. Because the structure of the steel has been destroyed by corrosion, it cannot be fully removed; even after togi, unevenness remains and the sword's aesthetic value is greatly diminished. Forced togi also risks damaging any hamon that survives.

For older swords in particular, managing pitting rust wisely determines the long-term value of the blade. Early detection and early treatment are the best measures to protect the blade. Maintaining proper storage conditions — especially humidity control and regular application of oil — is the most effective preventive measure against rust.

A Broken Blade — Repair or Preserve As Is

Joining a broken blade by welding is physically possible with modern technology. However, a weld-repaired blade loses significant value as a work of art and as an object of appraisal. The traces of welding remain clearly visible on the blade and are immediately identified as a restored piece by the eye of an experienced appraiser. In NBTHK (Society for the Preservation of Japanese Art Swords) examinations, weld-repaired blades are normally excluded from appraisal.

On the other hand, preserving both fragments in their broken state has its own significance. If the break was the result of actual combat, the broken blade holds academic and documentary value as historical evidence. Furthermore, because the internal structure of the blade, the quality of the iron, and the layers of tanren can be observed from the broken cross-section, the blade may acquire value as a subject of research.

Historical Combat Marks — "Wounds" to Be Protected as Evidence

Edge chips and scars remaining on the blade may be evidence of "battle wounds" — proof that the sword was used in actual combat. These are not mere damage; they are primary source material of academic importance that speaks to the sword's history and provenance. To repair them carelessly is nothing other than the permanent erasure of that historical evidence.

The balance between restoration and preservation requires a comprehensive judgment that considers not only artistic value but also historical and academic value. Old swords should be assessed from both their aspect as works of art and their aspect as historical documents, and decisions about restoration must be made carefully from both perspectives.

Togi (Re-polishing) — Restoring the Blade's Beauty

The most commonly performed type of restoration is re-polishing. The process in which a togishi progressively applies multiple types of whetstones in sequence to bring the blade to a polished finish is a precision task requiring expert skill. Re-polishing restores the blade's original brilliance and the beauty of the hamon, but at the same time it produces an irreversible change: each polishing makes the blade slightly thinner.

For old swords, repeated re-polishing over the centuries may have left the blade significantly thinned. If a togishi judges that further re-polishing would compromise the integrity of the blade, the option of refraining from togi and preserving the blade in its current state is chosen instead. Whether and to what extent togi can be performed is a specialist judgment requiring a comprehensive assessment of blade thickness, hamon condition, and value — a call that only an experienced togishi can make.

Consulting a Trusted Expert Is Always the Best First Step

It is strongly recommended that judgment on whether and how to restore a blade always be entrusted to a togishi or sword appraiser with specialist knowledge. Attempted restoration based on one's own judgment carries the risk of causing irreparable damage to value. A trusted expert will carefully assess the current condition of the sword and then judge — from the dual perspectives of the sword's value and its historical significance — whether it should be restored and, if so, to what degree. When in doubt about restoration, consulting an expert first is the first step toward protecting the sword.

As of 2026, the number of togishi specializing in sword restoration and togi remains on a declining trend, and finding an excellent togishi is itself a challenging task. Consulting the list of togishi certified by the NBTHK (Society for the Preservation of Japanese Art Swords) makes it easier to access reliable specialists.

A blade that has undergone restoration can maintain its beauty for a long time through proper storage conditions and regular care. Caring for a sword from both the restoration and the storage perspectives is the responsible form of ownership that will deliver beautiful swords to generations a hundred years from now.

Is "Reforging" or "Sai-ba" of a Broken Blade Possible?

Inquiries about "whether a broken blade can be reforged" are not uncommon, but to state the conclusion first: it is not possible to re-forge the broken blade and restore it to the original sword. While it is physically possible to use the broken fragments as raw material to forge a new sword, this means creating a separate, new sword — not restoring the original. The value of the work as that of the original tōkō and the validity of the kanteisho are lost.

"Sai-ba," on the other hand, is a technique of applying quenching again to a blade that has become yakemi (a blade whose hamon was lost in a fire or similar event) in order to re-create the hamon. Sai-ba has also been performed historically (the sai-ba of meibutsu swords burned in the Siege of Osaka is well known), but in appraisal it is recorded as "sai-ba" and is valued considerably lower than a blade with its original hamon. It is important to note that sai-ba is a salvage measure for yakemi and is not a means of repairing a break.

Approximate Costs of Restoration (As of 2026)

The cost of re-polishing varies according to the togishi's standing and the type of togi performed (whether base polishing only, or including kesho togi and sashikomi togi). In addition, for a rusted sword, a new shirasaya and new or repaired habaki are often needed at the same time, and depending on the extent of the damage, the total may exceed the sword's market value.

Before undertaking restoration, it is important to seek a specialist's opinion on the balance between post-restoration value and cost.

Where to Have Restoration Done and Notes on the Registration Certificate

Always have togi performed by a togishi who specializes in nihontō. Taking a blade to a cutlery shop or sending it to a knife-sharpening service will destroy the hamon and jigane in an irreversible way. To find a togishi, it is most reliable to obtain a referral through the NBTHK (Society for the Preservation of Japanese Art Swords) or through a sword dealer.

Note that even when leaving a sword with a togishi for restoration, the firearms and swords registration certificate must travel with the sword. For a sword whose registration certificate has been lost, the first step is to have it reissued by the Board of Education in the location where the sword is held (which requires a physical examination of the sword).

The Option of Parting with the Sword Without Restoration

If restoration costs are not commensurate with the sword's value, or if continued storage is difficult, the option of selling or transferring the sword in its damaged state also exists. Even damaged swords — zaimei kotō and swords with documentary value — may be appraised in their current condition. If you are unsure how to dispose of a sword, we recommend seeking a specialist appraisal, such as through a sword sale consultation, before choosing disposal (which involves consulting the police or the Board of Education together with the registration certificate).