Japanese Sword Maintenance Tools Complete Guide: Uchiko, Nuguigami, Choji Oil, and Mekugi-nuki

Why Knowledge of Maintenance Tools Is Necessary

Japanese swords are made of iron, so neglecting proper maintenance allows rust to develop, damaging the beautiful jigane (地鉄) and hamon (刃文) that have been carefully polished over the years. Conversely, improper care can lead to grinding scratches and encourage rust formation. Regular and proper maintenance is essential for preserving the aesthetic beauty and value of swords over time.

Japanese sword maintenance requires specialized tools, which are available as "maintenance tool sets" from sword dealers and specialty shops. This article explains the names, functions, proper usage methods, and precautions for each tool.

Uchiko (打粉)

Overview Uchiko is a small ball made of silk stuffed with white powder that is used to lift old oil from the sword blade. It is an indispensable tool in the first step of sword maintenance.

Components The typical uchiko consists of fine powder from uchigumori (内曇砥) stone wrapped in silk cloth. Uchigumori is a type of natural whetstone used for finishing polishing of swords; its fine particles work to lift old oil films. Note that this is a different material from tono-ko (砥の粉) powder derived from wood or whetstone dust, and care should be taken not to confuse them.

How to Use

1. Carefully withdraw the sword blade from the tsuka (柄) to create an unsheathed blade
2. Gently tap the uchiko ball on the flat of the blade (hiraji) so that white powder adheres evenly
3. Wipe away the old oil and uchiko together with wiping paper (described below)

Precautions

• Excessive use of uchiko can cause damage to the jigane because the stone powder has abrasive properties. Use the minimum amount necessary.
• Avoid striking strongly on the cutting edge (ha)
• If using monthly, in some cases you may only need to reapply oil without using uchiko

Nuguigami (拭い紙)

Overview Nuguigami (wiping paper) is a specialized paper for wiping the blade of a Japanese sword, characterized by its softness and tendency not to shed fibers. Using "hōshō paper" (奉書紙) or "tissue paper" as substitutes is not recommended because surface fibers may remain on the blade, and insufficient strength can cause the paper to tear, risking cuts to your fingers.

Types Commercial wiping paper comes in "thin" (usuguchi) and "thick" (atsuguchi) varieties. For blade wiping (oil removal), thin paper is easier to use, while soft thick paper works better for the final oil application.

How to Use

1. After applying uchiko, fold the wiping paper and slide it from the mune (棟) side toward the edge, wiping away old oil and uchiko
2. Because the edge is sharp, never touch the edge directly while it is upright; always use a sliding motion from the spine toward the point
3. Replace with a clean area and repeat wiping several times until no white residue appears

Precautions

• Wiping direction must always be from spine to edge. The reverse direction is dangerous as the edge can contact your fingers
• Strong force is unnecessary and will scratch the blade

Choji-yu (丁子油)

Overview Choji-yu (choji oil) is a specialized oil applied to the sword blade for rust prevention. The original material was essential oil extracted from cloves (choji), but modern commercial products often use mineral oil-based formulations. With low volatility, it forms a thin protective film on the blade surface to prevent rust.

How to Use

1. After finishing wiping the blade, apply a small amount of choji oil to cotton padding (or clean wiping paper)
2. Apply thinly and evenly across the entire blade—pay special attention to areas near the spine and tang (nakago), where rust tends to appear
3. The amount of oil should be "thinly gleaming." Thick application is counterproductive as dust and debris adhere more easily

Precautions

• Excessive application can cause oil to penetrate into the scabbard (saya), damaging the wooden interior
• Because choji oil contains plant-based components, it will degrade and oxidize if not replaced for long periods. A guideline is to replace it every 3 to 6 months

Mekugi-nuki (目釘抜き)

Overview This is a tool for removing the sword blade from the tsuka. It is used to remove the "mekugi" (目釘) pin inserted into the hilt. The mekugi-nuki is a thin rod-shaped metal tool with a tapered point sized to fit the mekugi hole.

How to Use

1. Position the tip of the mekugi-nuki on the mekugi (usually a thin bamboo or deer antler pin) on the side of the tsuka, and gently tap to push it out
2. Once the mekugi emerges, pinch it with your fingers to remove it
3. Point the tsuka downward and slowly withdraw the blade—rapid pulling is dangerous as the blade may fall

Precautions

• Striking the mekugi too forcefully can damage the wood near the habaki (a component fitted inside the hilt)
• Keep the removed mekugi safe to avoid losing it
• If the mekugi is stuck fast, do not force it; consult with a professional sword polisher (togishi) or hilt craftsperson (tsukashi)

Frequency of Maintenance and Storage Environment

The basic guideline for maintenance frequency is to replace the oil once every 3 to 6 months. However, during the humid summer season (rainy season through September), rust is more likely to develop; during this period, monthly inspection and re-oiling are advisable.

Store the sword in a sword bag (a specialized bag for swords) or sword box, kept indoors away from direct sunlight, condensation, and sudden temperature and humidity changes. When placing desiccant nearby, take care that it does not come into direct contact with the blade.

Advice for Beginners

Japanese sword maintenance is not difficult, but if you are unsure, the best learning method is to have experienced collectors at a sword dealer or sword appreciation event demonstrate the techniques for you. The Society for Preservation of Japanese Art Swords (NBTHK) and various local sword dealers also offer maintenance workshops. Acquiring the correct tools and correct procedures is the foundation for protecting treasured swords across generations.