How to make a hole in a wa handle of Japanese kitchen knife
The tang of Japanese kitchen knives are called push tang, narrowing tang or concealed tang which are not full tang of western kitchen knives. There is not a drill to make a straight and deep hole in a handle in the ancient times. It used to be making by concealed tang, putting tang between two piece of woods which has hole for tang.
Saya of Japanese Kogatana, a small knife with wooden saya is still made with this way. As a disadvantage, a craftsman needs a time to carve a hole carefully, what is more, it is difficult to combine texture of the surface of natural wood.
Nowadays, most of manufacturers put a tang into a deep straight hole of a handle. Although there are various ways to make a hole, wa handle manufacturers use a tool to make square or rectangle hole with hollow chisel, Kakunomi.
The Japanese blacksmith use a drill to make a deep round hole in a handle, then burn a shape with a metal chopstick which is exactly same shape of a tang.
You might already know, it is very difficult to make a straight hole according to the designed size. If you don’t have experience or introduced tools above, a drill driver or a drill press would be used to make a hole.