The Complete Guide to Japanese Sword Maintenance Tools — What Each One Is, What It Does, and How to Use It

Nuguigami is soft, absorbent Japanese paper — traditionally made from kozo (mulberry) fibres — used to wipe the blade surface clean of old oil, dust, and any particles introduced during handling. It is the first tool used in every maintenance session and the last, and it is the one most frequently used between full sessions.

There are two reasons for using nuguigami to wipe the blade: firstly, it preliminary removes any old oil and secondly, it removes any uchiko still attached to the surface of the blade. Nowadays it's becoming more common to use neru (flannel cloth), however when using a flannel, please remember that the fabric must be thoroughly washed and dried before being used.

What to look for when buying: genuine traditional nuguigami is soft, lint-free, and slightly absorbent. Avoid tissues, paper towels, or kitchen roll — these contain wood fibres that are abrasive enough to scratch a polished blade surface over time. A dedicated lint-free cotton cloth (neru) is an acceptable modern substitute for the paper.

Uchiko is a silk or cotton ball containing finely ground polishing stone powder. This specially formulated powder, composed of finely ground polishing stones, serves as a mild abrasive and highly absorbent agent. Its primary function is to eliminate any lingering microscopic moisture, contaminants, and residual oil from the blade's polished surface, ensuring it is perfectly clean before a new protective coat of oil is applied.

A critical distinction exists between traditional and modern uchiko: traditional Japanese maintenance kits often use Hon-metsuna-ko, a fine powder made from polishing stones. Some modern kits use talcum powder inside the uchiko ball — talcum powder is very soft and gentle, making it ideal for beginners and safe for regular cleaning, but it does not have polishing properties. For antique and high-value blades, traditional polishing stone powder is the correct choice.

Important limitation: Uchiko is mildly abrasive. Used correctly — lightly tapped, never rubbed — it causes no harm over a lifetime of use. Used too forcefully or too frequently, it can gradually affect the polish. For extremely high-value antique blades, some specialist conservators recommend omitting uchiko entirely and relying on nuguigami and oil alone. Consult your dealer's guidance for significant pieces.

Chōji abura (丁子油) — literally "clove oil" — is the traditional protective oil applied to Japanese sword blades after cleaning. It is oil used to prevent oxidation and rust, also commonly called choji-yu. Modern mineral oils or gun oils are not recommended as they can damage the blade over time. Ensure you are using pure choji oil, or a specifically formulated Japanese sword oil from a reputable source.

Traditional chōji oil is a blend of mineral oil with a small percentage of clove essential oil (typically 2–3%). The clove component adds mild antimicrobial and rust-inhibiting properties while giving the oil its characteristic faint fragrance. The oil's primary function is to exclude oxygen and moisture from the steel surface — creating a barrier that prevents oxidation.

What oils to avoid: avoid synthetic oils not specifically formulated for swords — they can damage the delicate hamon. WD-40, motor oil, cooking oil, and general-purpose machine oil are all unsuitable. They either contain additives that react with the steel, attract dust more aggressively than sword oil, or leave residues that are difficult to remove without damaging the polish.

The mekugi-nuki is a small brass or horn hammer used to remove the mekugi — the bamboo peg that secures the blade tang (nakago) inside the handle (tsuka). Without the mekugi, the handle will separate from the blade during use. The mekugi-nuki is used for the annual inspection of the tang, for cleaning inside the handle, and for replacing a cracked or worn peg.

A properly sized mekugi-nuki is essential to avoid damaging the mekugi or the tsuka. Avoid using metal hammers or other tools, as these can easily split the mekugi or mar the surrounding wood. Samurai inspected their mekugi every season and replaced it before a campaign — a cracked peg could turn the sword into an uncontrollable projectile. For collectors, a cracked or loose mekugi is both a safety hazard and a potential cause of damage to the nakago.

The mekugi themselves are bamboo pegs of a specific taper — thicker at one end than the other — which lock into position when pushed through the tsuka and nakago from the thicker (omote, front) side. Replacement mekugi should be included in any quality maintenance kit; they are inexpensive and should be replaced whenever cracked, loose, or significantly worn.

The abura-nuguishi is a dedicated soft cloth or paper used specifically for applying chōji oil to the blade — kept entirely separate from the nuguigami used for cleaning. A piece of wiping paper or flannel will do. The key requirement is that it is clean, lint-free, and has never been used with any abrasive or cleaning compound that could contaminate the oil.

Many collectors use a folded piece of nuguigami for oil application as well — this is perfectly acceptable, provided a fresh sheet is used and the oil applicator is clearly distinguished from the cleaning paper. Keeping them separate prevents accidentally applying a paper that has picked up grit from a previous cleaning session.

Strictly speaking the shirasaya is not a maintenance tool but a storage component — yet it is so integral to correct long-term care that no guide to maintenance is complete without it. A shirasaya is a plain, unfinished wooden scabbard and handle made from ho-no-ki (magnolia wood), used to house a blade that is not currently mounted in its decorative koshirae.

The wood is specifically chosen for its moisture-absorbing and humidity-buffering properties: it creates a stable micro-environment around the blade that moderates humidity fluctuations far more effectively than lacquered koshirae. A blade stored in its shirasaya, inside a kiri-bako (paulownia wood storage box) with humidity control packs, is the gold standard of nihonto long-term storage.

If your sword arrived without a shirasaya fitted to the blade's dimensions, acquiring one is strongly recommended — particularly for collectors outside Japan where humidity control may require active management.

A wooden hammer used to dislodge the blade from the shirasaya or koshirae in the case the blade is firmly lodged inside and cannot be dislodged by normal means — only used if necessary. A blade can become stuck in its saya when humidity has caused the wood to swell slightly around the blade. The kizuchi is used to tap the side of the saya gently to free the blade — never to force the blade directly.

If a blade is stuck in its saya, the correct approach is to hold the saya firmly with one hand and tap the wrist of that hand gently with the wooden hammer while allowing the blade to slide free under its own weight. Never attempt to pry or force a stuck blade — the risk of damage to blade, saya, and fittings is significant.