Case Study: Making the Sunahama Kotanto

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Forging a Kotanto Blade

A charcoal fire is used to heat the steel for shaping with hand hammers. I often use a heavy hammer for rough shaping and a lighter one for the finishing work. The shaping of a blade is divided into a hot and a cold stage, and each stage further divided into two steps. First a specific type of blank (sunobe) is forged, the shape of which will determine the finished dimensions of the blade. Then the blank is forged into the shape of the blade and allowed to cool slowly. The cold shaping begins with the profile and then moves to the bevels.


Forging the Blank (Sunobe)

In this stage, the volume of steel is allocated to each area of the blade and tang. This distribution will largely determine things like distal taper, proportions, and style of the blade, though the sunobe looks very little like its final shape at the end of this step. In traditional swordsmithing, a practiced eye can determine the outcome of a student’s test at the sunobe stage, without even waiting for the forging of the final shape.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The blade in the foreground is the raw material, a 24″ mill saw blade made of lovely steel that I have used for several projects.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The hammer that I use for most of the shaping work, made from a piece of axle (You Need A Japanese Swordsmith’s Hammer).
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tip begins as a reversed 45 degree angle, the longer side will become the cutting edge and tip.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed sunobe, the straight side will become the cutting edge once the bevels are forged in.

Forging to Shape (Hizukuri)

Forging a sunobe into the shape of a blade is a process of working up and down the steel a section at a time, forming the bevels and establishing the geometry of the knife. As the bevels are narrowed, the outward moving steel tends to curve the blade away from the edge, this must be anticipated and compensated for throughout the process. If it is not addressed early on, there will be no way to correct it later. Keeping the temperature as low as possible and forging almost into the black range each heat is one way to help refine the grain structure of the steel. Enough edge material must be left to have a 2mm thick edge after filing and before yaki-ire.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Back into the fire.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A spine view showing how the blade tapers away from the mune machi in both directions.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tang is forged very close to its final shape, but the notches for the mune machi and ha machi will be filed rather than forged in on this very small blade.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Forging with water on the anvil creates steam explosions which blow off the fire scale, keeping the steel clean and free of impurities.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After forging, the blade is cooled slowly in charcoal ashes to make it as soft as possible for the cold shaping and filing stages.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed forged blade, the notches for the machi have been marked with a file. The clean, smooth steel is a result of the water forging and carefully placed hammer blows.

Rough Shaping (Ara-Shiage)

This stage of cold shaping has two distinct steps, the first to outline the profile, and the second to establish the bevels and sides of the tang. Files are used to profile the blade in a blacksmithing leg vise, adjusting and refining each line slowly, removing to check the overall silhouette often. A sen dai (staple vise) and a sen scraper are used for the rough work on the bevels, filing and drawfiling for the final work. The edge should still be up to 2mm thick after all of the rough shaping is finished in order to reduce the risk of warping or cracking during yaki-ire.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The mune has been cleaned and straightened in the foreground, the notch for the mune machi is beginning to take shape.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed profile clearly shows the tang and the blade outlines now.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
At this stage, nothing has been done to the bevels yet, this is still the water forged steel skin.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The sen scraper is used remove the tough fire scale and to take down the excess material on the tang.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
One edge is established, then the other, and finally the material in between is removed.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Drawfiling removes the marks of the sen and levels the surface out.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tang is rough finished, the blade is next.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A view of the sen dai, showing how a series of wedges and blocks can quickly create a custom hold for any blade geometry.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A clear example of the technique of setting the finished height of each edge on an angle before removing the centre material.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Finished by drawfiling.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Compound angles and a non-marring grip created by multiple angled wedges in the sen dai.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Grinding with a slab of local sandstone to check the surfaces and get the feel of the geometry on a stone.

Clay Tempering a Kotanto Blade

Once the steel is shaped as much as possible in its softer state, it is coated with a thin layer of clay along the edge and a thicker layer on the body and spine. During the hardening process, the split second difference in cooling time caused by the clay layer creates two different hardness areas in the same piece of steel. The edge cools faster and forms a very hard steel structure called martensite while the body cools slower and forms a very tough steel structure made of ferrite and pearlite. The boundary between these two areas is called hamon and is commonly seen as a frosted wavy line down the length of a polished sword blade.

When the clay is fully dry, a charcoal fire is used to heat the steel slowly and evenly, taking care not to overheat any part of it. First the spine is heated to bring the whole blade to just below temperature, and then it is flipped over to focus heat on the edge. When the entire edge is at the correct temperature, it is plunged into a water bath, edge down, and held until cool (yaki-ire). The hardness is checked with a file and the process repeated if necessary. After hardening, the clay is removed and the steel is heated slightly again to remove some of the internal stresses (yaki-modoshi). Once this process is finished, and if the steel survives, the blade is ready for togi, hand polishing.


Preparing the Clay Mixture

The clay mixture does not need to have secret or exotic ingredients, but there are a few properties that are desirable in the final blend. The basic recipe is approximately a 1:1:1 ratio of regular clay, stone powder (saved from the polishing process), and charcoal powder. The clay provides the stickiness to keep it together and on the blade, the stone prevents shrinking while drying, and the charcoal helps prevent flaking off in the fire due to heat expansion.

The soft water source is snow or rainwater. Each ingredient is ground in small batches between stone and steel or two stones. Grinding and screening the ingredients as finely as possible is important, especially for the slip layer, as the layer can only be as thin as the largest sized particle.

Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
The partially dried clay before pulverizing. Clay sticks the ingredients together and onto the blade.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
Ground fine sand, silt, or polishing stone powder provides a filler that will counteract the tendency of clay to shrink and crack as it dries.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
Powdered charcoal being reduced to dust. Charcoal provides some micro pores as it burns out, allowing for some heat expansion and also affecting cooling time. More charcoal is added to the slip mixture than to the body clay mixture.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
In this case, fine steel filings and powdered iron oxide provide some thermal mass and make up part of the non-shrinking filler material.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
The steel and stone mortar and pestle stand-in.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
Powdered rust being ground between two stones, this will go into the body clay mixture.
Island Blacksmith: Traditional handmade nihonto style Japanese swordsmith techniques
Adding the rust to the body clay mixture before adjusting the water and thickness prior to application. A fairly runny but not watery mixture helps create a thin layer (think pancake batter not butter).

Applying the Clay (Tsuchioki)

The body and spine are coated in a thin layer of clay that will prevent the steel from cooling too quickly in these areas. A uniform thickness is important for even drying, heating, and cooling during various stages of yaki-ire. An almost runny but not watery mixture helps create a thin and even layer (think pancake batter not butter). When this layer is dry a very thin slip layer of clay that is higher in charcoal content is applied to the exposed edge, the charcoal burns out in the fire and the resulting porous clay surface has been found to cool steel faster than if it was bare. The clay slip also helps prevent oxidation and decarburization (loss of carbon at the surface) while in the fire.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The blade has been shaped with sen scraper and files to set the approximate geometry but the cutting edge is still 1-2mm thick. The extra thickness will help prevent cracking, warping, and carbon loss. The clean, rough surface will help the clay adhere to the surface.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A visible illustration of the two different clay layers when dry. The darker coloured thin slip layer is higher in charcoal and should have a very fine particle size. It covers the exposed part of the edge that will not be protected by the thicker body layer clay. Note that the spine curves slightly down to counter the upwards effect of yaki-ire.

Yaki Ire

This is the moment of truth for the knife, if it survives intensity of the quenching process it will become a live blade. If it succumbs to the stress and cracks it will become a piece of scrap steel again. Yaki-ire requires intense and singular concentration and even the best smiths lose one out of every four or five sword blades to the process. Even though all the work up to this point may be lost, the benefits far outweigh the risks when a good blade has been born.

In order to provide visual consistency for judging color and temperature, yaki-ire is done at night time or with doors closed and lights off. A charcoal fire is built and the water (heated up almost to boiling for modern spring steels) set near the forge. Not heating too quickly or too slowly, the blade is brought up to its critical temperature and committed to the water with a prayer.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
When working with steels less than a century old, the rain water bath is heated to the temperature of a proper ofuro to lessen the thermal shock to the steel by way of the vapour jacket.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Making sure the clay is completely dry by resting it on or above the glowing charcoal with no air blast for several minutes or longer.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Heating evenly and carefully, then the plunge when all is right. The blade is immersed up to the machi until it has cooled to the temperature of the water and then removed.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Out of the water to check for proper hardening, warping, or cracking.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After hardening, most of the clay has remained in place and the edge is fully hardened. The clay is partially fired after quenching, it is normal for some of it to come off in the water. A file is used to test if the entire edge has hardened fully, and if not the blade is cleaned, normalized, and new clay is applied to begin the process over.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A soft mild steel scraper is used to remove the clay mask. If there are no signs of stress cracking, the blade is cleaned and tempered over the remaining hot coals.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A slight amount of tempering applied to draw back the hardness of the edge slightly.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A test polish to inspect the hamon on a blade after a successful water quenching. A sun tiger #80 or lobstercarbon #120 waterstone reveals the actual placement of the hamon.

Polishing a Kotanto Blade

After the blade is hardened and tempered, the final geometry is created and the surface smoothed and polished with various abrasive stones. In contrast to other methods, stone polished blades have a different surface look and retain their crisp edges and lines. Polishing is broken into three distinct stages, the rough polish occurring before the fittings and scabbard are made, and the foundation polish and final polish once the rest of the knife is complete.

The word togi (研ぎ) does not differentiate between the action of polishing and the action of sharpening, for a Japanese sword the operations are one and the same, an integral process. A combination of Japanese waterstones, both synthetic and natural, are used to remove smaller and smaller amounts of steel and give the knife its final shape and surface. Each stone is progressively finer and is used with a different orientation so that the scratches from the previous stones may be clearly seen. Once they are erased, the next stone can be used, each time refining the geometry and surfaces towards the final goal. Once the rough polish is finished, work on the blade is halted until after the habaki, seppa, tsuka, and saya are created and fitted. This prevents accidental scratches while working on other parts of the knife.

Togi Dai - polishing bench for waterstones
A series of coarse synthetic and fine natural waterstones from Japan are used to refine and polish blades.

Rough Polish (Kaji-Togi)

At this stage, the large volume of steel left around the edge for the process of yaki-ire must be removed, and the blade and tang are given their final geometry. The edge of the blade is much harder than it was during the rough shaping stage and steel cannot be removed with any metal tools. A combination of natural and artificial waterstones are necessary for this process.

Care is taken to refine each part of the blade geometry and bring the planes into proper alignment and proportion beginning with coarse stones and quicker removal and ending with very fine stones and subtle adjustments. Tagane-ha (chisel edge) is a common technique for first establishing the centre line of the edge. Both sides of the edge are honed away on a 45 degree angle and then the excess material in between the edge and the spine is removed in sections, similar to the method of using a sen to set the pre-quench geometry after forging.

Island Blacksmith: Hand forged reclaimed tanto made with traditional techniques
A simple dry working station for coarse stones using a board with a hook over the edge of a stump. Coarse stones may be used dry and the powder saved for use in the yaki-ire clay mixture.
Island Blacksmith: Hand forged reclaimed tanto made with traditional techniques
A portable bench for rough polishing after the hardening process of yaki-ire. Water can also be used with this set up.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A very coarse waterstone is used to remove the bulk of the material at the edge, bring the blade very close to the finished geometry, and correct any major issues.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A #120 grit waterstone is used to clean up the deep scratches from the #80 grit and remove material from the edge until it is less than 1/4mm thick. Frequent careful checking ensures that any irregularities are corrected while there is still extra steel to work with.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Moving through several other waterstones from #180-#500 each is moved in different directions to erase the previous scratches. These stones largely set the finished geometry and bring the edge right to zero thickness (but not quite “sharp”). The final polishing will be done after all the fittings are made.

Process of Forging & Shaping a Kotanto Habaki

Once the blade is in rough polish, it is time to create a custom blade collar for it. This important piece of nihonto hardware is made specifically for each blade and is as complex as making a custom fit piece of jewelery. The function of habaki (鎺) are three-fold; the primary purpose is to secure the blade in the wooden scabbard without any pressure on the blade itself, the secondary is to provide a solid shoulder against which to mount the handle and guard, and the tertiary is to provide a stiffened and vibration-dampened flex zone across the transition from tang to blade and decrease the chance of failure at that critical intersection.

A standard habaki is fabricated from two parts; the jacket, which appears to be the entire habaki, and the machigane, a small compound triangular prism shaped wedge that closes the gap where the hamachi bridges the edge and the nakago no hagata of the tang. Most of the habaki is formed by forging, the final adjustments by filing, and the joining of the two parts by soldering or brazing. Once the habaki is fit, the blade is ready for a handle and the accompanying koshirae.


Forging the Blank

A correctly formed tang and blade are necessary prerequisites to making a functional habaki. The widest point of the knife must be at the area where the blade and tang meet on the spine, and a gradual taper in both directions as well as towards the edge ensures proper strength, balance, and the ability to assemble (and disassemble!) the koshirae. One of the main design points when creating habaki is that they should be quite thin at the front, especially near the spine as that is where they will slide as they are sheathed and unsheathed.

Copper is by far the most common material for habaki. With the exception of the initial bar shape, most forging may be done cold in between cycles of annealing to soften the work hardened copper. The final fit is always done cold in order to harden the copper.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A strip chisel cut from a reclaimed high voltage electrical bus bar, a source of very pure copper.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Hot forged into a bar of proper dimensions, this will likely yield enough to make two small habaki.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Cold forging out the taper in both directions from the spine (top to bottom, tang to blade) and leaving the thicker area above the mune intact.

Filing & Shaping

Forging in advance can save quite a lot of filing time later, and some judicious filing before folding can save a lot of trouble after the habaki is closed up. While the goal is to get as close as possible to the final shape, it is generally a good idea to leave some extra metal as the bending may not go exactly as planned.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Starting the notch for the munemachi is the most important step as filing it later is much more troublesome.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Using a chisel to remove it from the rest of the bar and cold forging the second side to match the first.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Cleaning up the back, note the thickness of the mune compared to the sides.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
This habaki will have a slight curve at the front, but there is plenty of excess metal here just in case.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
This butterfly is still pretty rough, but there is more forging to do after bending yet.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Using a tapered round punch on its side gives some radius to the inside of the mune. Concaving it slightly in along its length as well helps prevent it rocking on a high centre when the sides are bent up. Because it has been forged quite a bit already, this is as far as it will be bent before a second annealing cycle.

Bending & Fitting

The process of bending may require several cycles of annealing and forging depending on the accuracy of the original shaping. The sides are brought up and cold forged to the shape of the tang, being careful to work well back from the blade when hammering. When everything is fit well, the excess is cut and filed away and a small compound wedge called the machigane is forged and shaped to sit against the bottom of the tang in the gap where the habaki comes together.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
This is the second round of annealing during the bending processs, the habaki has already taken on much of its final shape and mainly needs to be thinned and adjusted at this point.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Most of the forging is done well back from the machi to avoid hammer contact with any part of the blade.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Cold forging the machigane from a scrap that was cut off the bottom of the habaki.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A dry fit after filing it to shape, showing how the machigane will sit against the tang and the hamachi. The habaki will not be bridged by the machigane all the way to the front which will allow the edge to flow out of it.

Soldering & Finishing

Heated in a charcoal fire, hard silver solder is used to join the machigane to the habaki in such a way that the habaki is slightly too small to slide all the way up to the machi. Hammering the copper after soldering hardens the habaki as it stretches it to its final dimensions.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The machigane in place before flux and solder are placed inside. A rusty steel wire provides pressure to the assembly, does not tend to stick to solder itself, and in this case makes a useful stand.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
When soldering in a charcoal forge, the air must be kept low and the piece placed away from the blast enclosed in a charcoal “oven” to create a reducing atmosphere.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Cooling slowly to ambient temperature avoids thermal shock that could cause the solder and base metal to pull away from one another.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
After soldering the copper has a layer of black copper oxide, as beautiful as it is, it is very brittle and would not stay intact during the final forging.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
In this case, a file was used to clean off the black copper oxide and create a subtle yoko-yasuri pattern. Then the habaki was reheated and very quickly transferred into hot water with a trace of borax in it. This type of fired copper is called hi-do (緋銅, fire copper), the technique causes stable red copper oxide to form instead of the brittle black oxide. The copper in the photo is fully cool, though it looks as though it is still glowing a beautiful red orange colour.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The red oxide does not break off when forged and the habaki can be work hardened as usual, stretching it out to fit tightly in place.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The fit at the mune machi showing how the slightly rounded hira/kaku mune style I am calling komaru mune continues into the habaki, rather than having the usual peaked iori mune shape. The habaki should follow the shape of the spine smoothly as it will rest there for drawing from and inserting into the saya.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The final area to work with files is the shoulder that sits against the seppa, it should be square and flat, and should be at 90 degrees to the mune at the munemachi.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Waterstones are used to flatten and polish the shoulder, and usually the rest of the piece, but in this case the red oxide hi-do is the desired finish.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Polishing with fine stones and charcoal is usually saved until after the tsuka and saya are made, but in this case the patina is already in place and must be carefully preserved during the other stages. Ibota wax is hand buffed onto the surface with a cotton cloth to deepen the colour and provide a glossy layer of protection.

Carving & Shaping a Kotanto Tsuka

Once the habaki is made, it is time to create a handle for the blade. 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. This kotanto 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.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Copper water pipe is annealed in the forge, split with shears, opened, and hammered flat.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A rough opening is cut with a small chisel, as large as possible while still leaving enough room for a clean filed edge.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The nakago-ana is enlarged and cleaned up using escapement files.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Measuring from the top and bottom of the habaki rather than from the opening, the shape is laid out and chiseled, cut, or filed and then polished on waterstones.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The finished seppa provides measurements to sketch out the rest of the koshirae.

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 (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 forged kotanto made from reclaimed and natural materials
This block was nicely straight grained and split very well with an oversized cleaver acting as miniature froe. Splitting the rough block ensures the grain is fully aligned with the blade.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
It is common to saw the tsuka in half and then plane it flat, but for this small piece I was able to split it in half as well. This will give the glue a larger surface area for gripping.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Beginning to carve the omote side. The ura side is not carved until after this side is close to finished dimensions.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
For the final fitting, the tang is wiped with oil so that it will show up uneven points of contact with the wood. Scraping with slightly curved kiridashi is a technique for refining and smoothing the inside.

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.

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 or tsukaguchi rather than a floating tsuba.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Core parts ready for assembly, note that the glue layer is very thin.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Tightly bound with an even winding and pressure, then tension is increased with wooden wedges in certain areas.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
After drying 24 hours, the front of the block is leveled and trued using a granite slab.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Pacific Yew sawn to size and cleaned up on the granite slab. Double edged saw has both rip (top of photo) and crosscut teeth (bottom of photo).
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A kiri is used to open several holes to rough out the nakago-ana. There are several different styles of kiri bit, this one is a three sided type forged from an expired file. Kiri give great control and can be used much more precisely than a standard modern drill bit.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Small coarse files are used to complete the nakago-ana in the ki-fuchi and the piece is cut to size.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The piece is aligned and bound with the tang in place and then once stable, the tang is removed for drying.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Squaring up the block to the ki-fuchi. A saw file removes a lot of material quickly without deep scarring like a rasp, using a plane in this situation would be difficult because of the cross-grain of the Pacific Yew.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Opening filed to fit the tang.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Drilling the mekugi-ana using a hand powered post drill. The location on the tang is chosen based on an estimate of best placement on the finished handle, and then the actual hole in the handle is placed based on the location of the hole in the tang. The opening in the tang will be enlarged and adjusted using a round file in the final fitting.

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.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Using a kiri to begin the mekugi-ana, it will be enlarged with a small round file.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Carving the profile down nearer to the finished outline.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Carving the ki-fuchi nearer to the finished shape, based on a tracing of the seppa.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Matching the front of the tsuka to the ki-fuchi.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Tapering the sides back towards the kashira.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Tapering the corners back towards the kashira.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
This would have been the look if the mount was to be a simple wooden kaiken, but this will become a small aikuchi mount.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Setting the depth for the wrapping with a coarse file and carving the core down to meet it.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The tsuka growing out of its block of origin, not much more can be done while it is still attached.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Separating the tsuka from the remains of the block.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
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. My theory is that they serve as a reference point for registering the position of the handle and direction of the blade by feel.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The Pacific Yew for the ki-kashira is cut roughly to shape and glued on to the tsuka core.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The outline has been established, next the contours of the end are carved and smoothed.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A subtle tribute to the yama-no-michi, it will become even more subtle in the finished design.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Smoothed out showing the grain. The ki-kashira is bookmatched with the ki-fuchi so the swirls in the grain mimic each other.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The finished wood tsuka core. Steps remaining are to coat the Pacific Yew with 100% pure Tung oil and add the wrapping to the handle.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A coat of 100% pure Tung oil brings out the natural glow and colour of the Pacific Yew. Like Walnut and Linseed, Tung oil penetrates the wood cells and then cures, sealing itself in and helping keep moisture out.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A size comparison for scale. This is an antique wakizashi shirasaya tsuka (measuring a generous hand and a half) which is closer to the finished size of the whole kotanto and saya than to the tsuka itself!

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 due to budget constraints. 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.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Making and adjusting the paper pattern. Paper does not conform well to compound curves unless wet formed, so this is an approximation.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Shaving down thick areas of the skin from the back. Cutting the skin is a challenge as each node is like a bead of glass.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Dyed paper glued with sokui where the seams and edges of the samegawa will fall. Very reminiscent of sashimono nobori, samurai banners, somehow.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
After the skin is glued and fine adjustments are made to placing the seams and edges, it is wrapped tightly with a leather cord to dry.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Omote side with the finished black samegawa wrap.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Ura side, the samegawa meets along the centre, running through the mekugi-ana.

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.

Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Creating the taper with chisel and coarse files.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Rounded and smoothed, then burnished with antler.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
Finished and ready to drive home for the final mounting.

Carving & Shaping a Kotanto Saya

Once the tsuka is made, it is time to create a saya (scabbard) for the blade. The saya should fit snugly on the habaki, with most pressure to the top and bottom, and should hold the blade securely without rattling or jamming. The lines and proportions must be appropriate to the blade and handle and take into account the appearance of the whole unit.

Similar to the process for tsuka, a saya is shaped 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 carved, planed, and shaped. As with the tsuka, the lower part of the blade is placed slightly off centre in the block so that the edge is fully supported by wood rather than resting against the glue joint.


Carving the Inside

Creating a saya is begun by selecting an appropriate block of wood, sawing or splitting it into halves, and carving out each half to guide the blade smoothly. Carving is done with purpose designed chisels called saya-nomi (鞘鑿). The mune should be centered in the block of wood but the small flat surface for the edge should be fully seated in the omote half of the wood, slightly to one side. The purpose of this is to align the wood with the tsuka and keep the edge from splitting the glue joint if it ever makes contact with the saya. When the fit is just right and the blade sits 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 forged tanto made from reclaimed and natural materials
The omote half is carved first, starting from the spine and moving across to the edge. The edge sits against the inside of this half fully which puts any potential stress against wood rather than against the glue joint.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The two halves are glued back together with sokui and wrapped with a leather strap to provide tension, wooden wedges increase pressure where necessary.

Shaping the Saya

The outside work is carried out using chisels, planes, and occasionally coarse files. The block is first squared up and then taken down to the rough dimensions. The shape of the koi-guchi (saya opening) is marked and carved and then the rest of the block is chiseled down to meet it. A plane is used to smooth and true up the surface and final sanding is done with tokusa (horsetail plant, equisetum hyemale, 砥草, “to” as in togi) glued to wooden blocks with sokui (rice paste glue).

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Tracing the seppa sets the dimensions for the koiguchi.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Extrapolating the sketch down the saya from this tracing ensures that the handle will flow properly into the saya.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The block is squared up to the tracing of the seppa.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The block is tapered down from the koiguchi to set the profile.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
A chisel or knife is used to carve the koiguchi down to meet the seppa outline.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
The corners are removed and the shape refined. Tokusa gives a finish that is a cross between fine sanding and burnishing, but does not leave grit as sandpaper can.
Island Blacksmith: Hand forged kotanto made from reclaimed and natural materials
At the client’s request this will be a cross between a nurizaya and shirasaya, receiving only a 100% pure tung oil finish to show the spalting and woodgrain.

Foundation Polish (Shitaji Togi)

Once the fittings and scabbard are complete, the blade is first given the rest of its foundation polish and then the final polish. Depending on the condition of the blade, the last used stone (#300, #500, or #700) may be repeated again to check that there are no new scratches from the workshop and then finer and finer stones are used to complete the finish.

Most of the foundation polish is carried out with natural (or high-quality synthetic) Japanese waterstones which cause the hamon and other steel activity to show up against the body of the blade. A Japanese waterstone forms a slurry like fine clay with suspended particles in it, water (sometimes with a little baking soda to combat rust) is used to control its viscosity and how much stays on the stone during use. A natural stone gives a nice subtle finish with a unique look due to its slight variation of hardness and grit size.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
As the stones get finer the internal structure of the steel begins to be revealed.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The hamon becomes more visible and the surface scratches finer and finer.

Final Assembly

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Parts ready for assembly.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Koshirae and blade.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Kotanto and saya.

more information on the finished knife here: Sunahama Tanto

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