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 prepared. 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.

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.


Choosing and Preparing the Blank

The core of the handle is traditionally honoki (朴の木, hou wood, Japanese Bigleaf Magnolia, Magnolia Obavata), chosen for its low moisture, low acidity, stability, relatively straight grain, and balance of cushioning and strength for tsuka and saya.

The wood should be dried and seasoned for as long as possible, usually five years or more and at least a couple of them right in the working space. Shirasaya require very clean and clear grain but nurizaya can contain some cosmetic artifacts or colour variations as they will be lacquered over later.

Grain that runs relatively parallel to the curve of the koshirae is both structurally and visually advantageous, particularly in the handle and upper area of the scabbard where the most stress will be. It is possible and sometimes necessary to remove a slight wedge shape between tsuka and saya to keep the grain aligned in the best way possible without interrupting the flow. Creating a tsuka is begun by selecting an appropriate block of wood and sawing it into halves and planing the inside surfaces flat.

Tsuka and Saya Carving
Seasoned Magnolia slabs for processing and carving into scabbards and handles.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Planing the Magnolia wood blank smooth after sawing in half lengthwise.

Carving the Nakago-ana

After the blank is sawn into halves and planed smooth, the decision is made where the line between handle and scabbard will be cut, then each half of the tsuka is carved out carefully to seat the tang in place. Carving is done with purpose-designed chisels called saya-nomi (鞘鑿).

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.

Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Carving the inside of the tsuka halves to fit the tang snugly. The omote is carved first and then the ura, working from mune to ha in each half.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
The mune is equally divided between the blocks, but the nakago-no-ha rests entirely in the omote half.

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.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Cooked Japanese short grain rice, the tastier the better. More than a small bite’s worth will take a long time to mix and produce far too much glue…unless you are making shoji!
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Mashing it together helps break up the grains, pulling it out under the wedge in small amounts will help crush the pieces into paste.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Once there are no pieces left at all, it is time to add a small amount of water to thin it a bit.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The final consistency should be as thick as possible while still easy to spread in a thin layer. Too much water will weaken the joint and increase the drying time, too little makes it hard to spread thinly and evenly.

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.

Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
The fit and placement is carefully checked, care is taken not to allow any excess glue to leak or remain inside the opening.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Cord and wedges provide pressure overnight as the sokui dries.

Shaping the Tsuka

Planes, chisels, knives, rasps, and coarse files are used to turn the block of wood into a graceful handle shape and smooth the contours. Starting from the profile of the fuchi, 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. Finally, extra wood is removed to make room for the wrapping to come.

Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
After roughly mapping the handle shape on the side, the tsukaguchi is carved down to match the fuchi.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Once the fuchi fits the lines of the four surfaces are carried back from it for the final dimensions.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Once the kashira fits and the rough shape has been carved the refining process begins.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Approaching the final dimensions and shape for the tsuka details, accounting for the thickness of the handle wrap subtracted from the thickness of the fittings.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Tsukigata were originally designed to make room for the end knots to sit lower on wrapped handles, however they are often included on the omote side of unwrapped handles as well. A personal theory is that they can also serve as a reference point for registering the position of the handle and direction of the blade by feel.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
The mekugi-ana is drilled in the tang and filed to shape.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
The placement on the tsuka is marked as closely as possible.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
The mekugi-ana is drilled with a kiri, with the tang in place to help guide the kiri, and then cleaned up and adjusted with a small round rasp after removing the tang.

Applying the Samegawa

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.

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. The samegawa is dampened and formed around the tsuka several times as it is adjusted. Once it is finally dry and perfectly fit, the skin is carefully glued in place with sokui and bound with string until dry.

Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Transferring the paper tsuka pattern to the back of the samegawa, washi paper can be formed to compound curves when slightly dampened.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Edges can be cleaned up with a sharp file and some care.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Soaking just long enough to provide flexibility but not so long as to completely soften the material.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Wrapping with string to form it until dry, adjusting and repeating as necessary, then once dry it is glued with sokui and wrapped to dry.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Once the samegawa has dried in place the mekugi-ana is opened up to match the tsuka core.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
An example of the ura side, the samegawa should meet cleanly along the centre, running through the mekugi-ana.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
An example of the omote side, samegawa exactly following the contours of the wooden core underneath.

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. Looking endwise, 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.

Mekugi for swords should be made from smoked susudake bamboo for strength, but horn, hardwood, and sometimes metal mekugi are found on antique tanto koshirae. Leaving as much of the denser exterior material as possible down one side, the bamboo 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. The ends are sealed by soaking or saturating with 100% pure tung oil and allowed to cure for two or three weeks.

Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Susudake is century-old bamboo from the ceiling of an old kominka farmhouse, darkened and hardened by decades of smoke wafting up from the irori cooking hearth.
Island Blacksmith: Hand crafted tanto koshirae made from reclaimed and natural materials using traditional techniques
Carving mekugi from horn requires observing the grain structure as with wood or bamboo.

The next step in the process is Carving the Saya, or scabbard.