Making Santoku - Part 4

Traditionally, Japanese knife handles consist of bone for the handle and buffalo horn for the bolster. I like to add a piece of bone between those two. Purely for aesthetic reasons. So, the making of the handle begins by shortening the tang to an appropriate length so it is hidden inside the handle, and by cutting down to the approximate size of a piece of each of the selected materials.

I drilled a 2 mm pilot hole in the horn, and I burned the rest with the tang of the knife heated with a blowtorch. That way, I got a fitting hole very quickly. The bone could be drilled very roughly; an exact fit there is not necessary. When the horn and bone were fitted and glued together into one piece, I polished the front face

After this, I proceeded with the wood. There I drilled a slightly larger (6 mm) pilot hole and burned the rest with a heated tang too. That way I got a relatively snug fit for the tang. In a traditional Japanese knife this would be enough, but this is where I differ from that again.

I cleaned the tang with a 40-grit belt and cut a series of grooves into it with an angle grinder. This way, I got a clean, rough surface to which an epoxy glue can adhere strongly. I prefer glued-up knives instead of a simple friction-fit. To be honest, I do not see the point of a kitchen knife that can be disassembled.

For glue-up, I am using a Spanish windlass to keep the parts together until the epoxy sets. It does not need to apply huge pressure, just enough to keep the parts from shifting. I used slow-curing epoxy, and in the first few hours before it gels, I checked the fit regularly. The piece of wood wasn't too big, so I couldn't just glue it on however and then remove excess material for a symmetric knife; I had to be reasonably close to the final shape already.

Gluing went smoothly, so I could grind the handle shape the next day. Normally, I do this freehand until the knife "feels right", but this time I had specific measurements that I had to work towards. I could not get them exactly, but I did get reasonably close. After the profile was ground to the desired size, I ground the cross-section to an octagonal shape, and I polished all surfaces all the way up to 600 grit. Usually, 300 grit would suffice, but olive wood has really small pores, so I went higher.

With the handle shaped, the knife is almost finished. All that remains is to apply a surface finish to the wood and then to sharpen it.

Olive wood is not only dense with very small pores, but it is also naturally oily. That has three consequences – it stinks when worked something awful, it gums up abrasives, and it can't be stabilized with epoxy resin. ( Gluing the tang would be problematic for this exact reason too, but burning the hole solved that problem by burning the surface inside it, thus evaporating/burning the oils on its inner surface and making it suitable for glue adhesion.)

For this reason, I am finishing the surface with tung oil. This is easy, but slow – every day, I smear a drop of tung oil on the surface, wait until it seeps in, then wipe the excess and wait for a day. After five days, it appears that the oil no longer seeps into the wood, so now I am waiting for two to three days until the oil hardens properly. Tung oil is not as hard as epoxy, but it is noticeably harder than other drying oils.

So that is where I am now, and unless something bad happens, the knife should be ready to send off next week.