When the cold and dry weather drags, on, the shinai become more vulnerable to splits. When you keep training with a shinai that has splits it can be incredibly dangerous. You can get splinters in your fingers or in your eye, and there has even been a reported case of someone accidentally swallowing a splinter! Simple negligence can put not only yourself but also your opponents at risk of injury. To avoid such accidents, it is mandatory that you check your shinai before and after training.
Yet, if you keep training the shinai will inevitably become damaged. In this article I would like to show you how to repair the splits in the shinai. The things you need to prepare are: a shinai-sharpener, shinai-file, walnut oil, tissue paper, old newspaper, and working gloves.
First, spread the old newspaper on the floor so the floor does not get dirty. Prepare the damaged shinai to be taken apart. You first remove all the parts like the hilt-leather (tsukagawa) and the top-leather (sakigawa). You can remove shave off the splits even with the tsukagawa on, but there is a chance of creating small cracks in the inside of the bamboo, which can cause bigger cracks, so it is recommended that all parts be removed. Most shinai have glue stuck to the tilt so do not remove it by force. Instead, use a woodchip to gentle knock the tilt and slowly remove the glue.
After you have dismantled the shinai, check the back of the bamboo to see whether there are numbers or marks. When re reassemble the shinai, if you do it in the wrong order, the force will be applied in the wrong direction which can cause cracks. It is good to write on the back of the bamboo, write “up” or “right” so you know later.
Next, use the shinai-sharpener (shinai-kezuri) to shave off the parts that have splits. Make sure you shave it in one direction only, from the outstretched part to the sword point. If you shave it the other way, towards the tilt, the fiber of the shinai gets stuck and worsens the split. Also, try and shave a wider area, not only the part that has the split. If you only shave the part with the split, that part becomes caved in and vulnerable to more splits.
When the splits have been removed, use a shinai-file (shinai-yasuri) to file the surface that has just been shaved. This smooths out the surface and makes it more resistance to splits.
Lastly, sop some walnut oil(or camellia oil) into tissue paper rub it into the shinai. When oil is inserted into a dry shinai it becomes more durable. Walnut oil is most suited for the shinai, but if you cannot find it salad oil is a good substitute.
After that, reassemble the shinai and the work is complete. There are many other approaches to maintaining the shinai, but I hope this way can be helpful to you.
I hope everyone can keep training safely by careful maintenance of their shinai!