Another very hot day continues today, with the temperature rising above 30°C. The end of the rainy season was announced yesterday in western Japan, and it will probably be announced in our area soon as well. Today, I attached the sliding key panels to the 3-sun puzzle boxes. I did not work on all the boxes currently in production, but only about twenty with natural wood designs. Normally, I attach one side each day, but because there were only a small number this time, the work went quickly. I attached one side in the morning and the other side in the evening. I sometimes do this with 3-sun puzzle boxes. Since the panels are small, they do not warp very much, so it is not a problem.
The photo shows the panels being attached. One side has already been attached, and I am now working on the final side. As usual, the panel is made by cutting a single piece of walnut into three parts. The center part is the sliding key and moves. For the 3-sun box, the small wooden piece inside, called the Bocchi, is only 6 mm, so I need to be very careful with the glue used there. If the glue spreads out, it can stick to the panel beside it and stop the mechanism from moving. Even if it still moves, the dried glue may remain as a small lump and prevent smooth movement. The glue we use is woodworking glue, and it is made from a kind of plastic-like material. This vinyl- or plastic-like material does not slide well at all. If it gets onto a moving wooden part, it creates friction and makes the movement feel rough. So, I have to be careful not to use too much.
When the glue is first applied, it sits slightly raised on the surface. When the panel is put on place, the glue is crushed and spreads out.So, I need to allow for how much the glue will spread and apply it so that it does not go beyond the 6 mm width in this case. Once the panel is attached, the glue point can no longer be seen, so if the mechanism does not move later, it means too much glue was used. Since 6 mm is a very narrow width, I have to apply the glue in a very thin line so that it spreads out and stops just within that 6 mm area. However, if I use too little, the joint will not be strong enough, and the small wooden piece may come off after the sliding key has been moved many times. On a 3-sun puzzle box, the glued area of this small wooden piece is only about 6 mm x 16 mm, so ideally, I want to cover the whole area with glue. Many craftsmen make a small groove by chamfering the corners of this piece, so that even if some glue spreads out, it will not reach the panel beside it. I do not do this. As long as the glue does not spread out too far, it is fine, so I apply it by relying on experience. After making many of these for decades, you gradually get better at it.
