Proper shinai maintenance is one of the simplest—and most important—habits a kendoka can develop. A well‑cared‑for shinai keeps you and your training partners safe, improves the feel of your strikes, and helps your equipment last significantly longer. Whether you’ve just bought your first shinai or you’re looking to refine your routine, here is a concise guide to keeping your weapon in top shape.
Before the First Use:
1. Smooth the Slits with Scratch Paper
New shinais often have slightly sharp edges along the slits.
Running a piece of scratch paper (or very fine sandpaper) gently along the edges helps smooth them out.
- This significantly reduces splinters,
- Makes the shinai safer to use,
- And contributes to longer life of the bamboo.
2. Tighten the Tsuru
The tsuru, the synthetic string running along the back of the shinai, keeps the structure stable. Before your first practice, tighten it firmly so the bamboo remains securely bound.
3. Tighten the Nakayui
The nakayui—the leather knot around the slits—must also be tightened before use. A properly adjusted nakayui ensures that the shinai bends correctly on impact and maintains its intended shape.
4. Write Your Name on the Tsukagawa
It’s a small step, but essential.
The tsukagawa (leather hilt) is the best place to mark your name, ensuring your shinai finds its way back to you if it gets mixed up with someone else’s.
Ongoing Maintenance
Regular Inspection
Your shinai should be checked frequently, ideally after every practice. Look for:
- Splinters along the slits
- Cracks in any of the bamboo staves
- Worn or damaged leather parts (tsukagawa, nakayui, sakigawa)
If your shinai is stored in a cold, dry place—something you should avoid—it is especially prone to drying, cracking, and splintering. Regular checks are even more critical in those conditions.
Re‑Tighten the Tsuru and Nakayui
Both the tsuru and nakayui will loosen with use.
Make it a habit to retighten them periodically so the shinai performs as intended. Make sure that the nakayui of your shinai is at approximately the 1/4 of the shinai, and 1/3 of the “blade.”
Monitor Leather Stretching
All leather stretches over time. This means that e.g. the tsukagawa can gradually lengthen, subtly affecting the shape and feel of the grip.
If you notice this, you can shorten or adjust it—or replace it if necessary.
Repairing Issues When They Appear
Splinters
Remove splinters immediately.
Left untreated, they can deepen cracks or injure someone during keiko.
Cracks
Never use a cracked shinai.
If a stave has cracked, retire it immediately or replace that stave.
Broken Bamboo Slats
If one of the staves breaks:
- Replace it with another stave from a similar shiani (if you have some leftovers), or
- Use one from a similar shinai if necessary.
Mismatched slats may create what some jokingly call a “frankenshinai.” Sometimes these hybrid shinais turn out surprisingly good—other times, not so much.
Storage and Conditioning
Some kendoka:
- Oil their shinai (lightly, with e.g. linseed or camellia oil) to preserve flexibility,
- Or store them in humid areas, like bathrooms, to prevent drying.
These methods are optional and vary, but both can help maintain flexibility and reduce cracking.
Safety First—Always
If you notice any of the following:
- Splinters
- Cracks
- Loose or damaged leather
Fix the issue immediately—for your own safety, and for the safety of everyone you train with.
Additional Help: Tutorial Videos
To assist you further, here’s a list of helpful video resources on shinai maintenance.
Kendo Gear: Types of Shinai and Shinai Maintenance – by The Kendo Show
https://www.youtube.com/watch?v=CjEpeQcwsYA
How to tie the tsuru (string) on your shinai – by Shogun Kendogu
https://www.youtube.com/watch?v=q_d7B9oqxYo
Fastening the Nakayui – by Kendo-Sport
https://www.youtube.com/watch?v=hrIogv2p9bg
Shinai Assembly & Maintenance – by m uch
https://www.youtube.com/watch?v=XQ5cFLWZei0
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