Process of Carving & Shaping a Tanto Tsuka
Once the habaki is made, it is time to create a handle for the blade. Before starting to carve the wood core, any additional hardware such as seppa (washer), tsuba (handguard), fuchi (ferrule), or kashira (pommel) are usually made. Because of the tapering shape of the tang, the handle can be designed to be easily removable for cleaning and sharpening the blade. If the handle is to be finished by wrapping with rawhide, leather, or ito (flat silk cord), these must be also planned into the design. The kotanto depicted here will have an all wood handle with a samegawa wrapping and no tsuba, so the only additional hardware required is a seppa, a thin metal washer for the habaki to shoulder against.
A tsuka is created in two distinct stages, first the wood is split and the inside carved to receive the tang, and then it is joined back together and the outside is shaped. To increase strength, the tang is placed slightly off centre in the block so that the nakago-ha (bottom edge of the tang) is fully supported by wood rather than resting against the glue joint.
Making the Seppa
The seppa may rest against the tsuba or fuchi, or in this case against the front of the tsuka. The outline of the seppa will determine the profile of the handle so it is very carefully planned in the context of the finished project.
The opening should be large enough that the tang does not actually touch it but small enough that the habaki can cover it. A punch is used to spread some material from the the top and bottom corners and they are adjusted to grip the corners of the nakago mune and the nakago-ha. Seppa are usually fairly simple, but various patinas, filework, hammer textures, or chisel marks can be used to add interesting details.
Carving the Nakago-ana
The core of the handle is traditionally honoki (朴の木, hou wood, Japanese Bigleaf Magnolia, Magnolia Obavata), and my favorite local island stand-in is Nootka Cypress as it is a similar density clear, straight grained wood that carves nicely and provides a comparable cushioning and strength for tsuka and shirasaya.
Creating a tsuka is begun by selecting an appropriate block of wood, sawing or splitting it into halves, and carving out of each half to seat the tang in place. Carving is done with purpose designed chisels called saya-nomi. The nakago mune should be centered in the block of wood but the nakago-no-ha (bottom edge of the tang) should be fully seated in the omote half of the wood, slightly to one side. The purpose of this is to keep the tang from placing strain on the glue joint, resting it fully against wood. When the fit is just right and the tang sits tightly in place, the two pieces of wood are joined back together with sokui (rice paste glue), and the handle carved and shaped once dry.
Making Sokui (Rice Paste Glue)
Sokui is a simple wood glue made from rice that is traditionally used for joining wood from tsuka to sliding panel shoji. The all natural glue contains nothing but delicious Japanese rice and a little bit of extra water. One of the reasons rice glue was originally chosen for making tsuka is that it is non acidic, does not degrade either the steel or the wood over time, and does not retain moisture. Another is that, while quite strong, it is not stronger than the wood itself. This allows a scabbard or handle to be split open for cleaning or repair without damaging the wood.
A bite or two of cooked rice is placed on a board and worked with a bamboo or wooden wedge to break all the grains into pulp. As the rice is squeezed under the wedge it becomes like sticky dough. Once there are no pieces left, a few drops of water is worked in to bring the glue to the desired consistency. It should not be runny but should be thin enough to spread evenly on the parts to be joined.
Gluing the Core
A thin layer of glue is spread on one or both tsuka parts, depending on the consistency of the glue. The two parts are tightly bound with a cord or leather strap and wedges further increase the pressure. Using a strap rather than clamps provides an even, non-marring pressure even when the block is not yet perfectly square and true.
This small tsuka will have an unusual ki-fuchi, a wooden accent in place of a fuchi. Pacific Yew is a relatively hard and dense wood with a beautiful rich orange colour and natural gloss. In this case, the accent will be attached to the tsuka and have the grain running vertically to add strength and stability, making it functionally more like a true fuchi rather than a floating tsuba.
Shaping the Tsuka
Chisels, knives, rasps, and coarse files are used to turn the block of wood into a graceful handle shape and smooth the contours. This would be the final stage for a wooden handle or shirasaya, but this piece will be finished by wrapping over the core with samegawa. Starting from the profile of the seppa, the shape of the handle is carved at the fuchi and then carried back by stages, working from a squared taper to a rounded one. Extra wood is removed to make room for the wrapping to come.
Wrapping the Tsuka
An additional layer of strength, grip, durability, and embellishment is often added to the wooden tsuka using a rawhide wrap and leather or silk cord. Deer rawhide is sometimes used, but most often samegawa (ray skin) is seen under formal wraps or on its own. Rawhide is stiff and strong, and samegawa in particular has a good grip for the hand or for locking in place any cord that wraps over it.
Ordinarily black samegawa would be created by coating over the rawhide with urushi (natural laquer). In this case a tanned and dyed samegawa will be used for its beautiful appearance, texture, and glassy shine. A paper pattern is made to determine as near as possible the shape of the samegawa needed and then a piece is cut slightly oversize and trimmed down bit by bit. Because the leather is black and the wood very light, strips of dyed paper are glued in place under each of the areas where the samegawa will end. Once this is fully dry, the skin is carefully glued in place and bound with leather cord until dry.
Making the Mekugi
The Japanese sword is unique in its handle engineering as well. The tsuka and nakago are shaped and fit together in such a way that the strength of a single bamboo peg holds the whole unit together and so that removal of the peg allows complete disassembly. This allows the blade to be easily removed for cleaning and sharpening and allows for replacement of the mounting without damaging the blade in any way. In addition to being inserted from the omote side, it is important to note that mekugi also have a correct orientation in the mekugi-ana. The part of the mekugi with the most dots is the outside of the bamboo plant and the strongest. It should be rotated towards the back of the handle, where the nakago places the most strain on the peg.
Because this is a tanto, and a small one at that, the peg need not be bamboo as with a sword. Horn, hardwood, and sometimes metal mekugi are found on antique tanto koshirae. In this case the deep red wood is drawing to mind the colour of an urushi laquer finish. The wood is shaved to a rough taper with a chisel and then smoothed with coarse and fine files as it is slowly adjusted to a final fit before being cut to length. Antler tip leaves a glossy burnished surface and the ends are sealed with 100% pure tung oil.
The next step in the process is Carving the Saya, or scabbard.