Guards for classical Japanese style takedown knives are generally formed as variations of flat discs that slide over the tang. When working with wrought iron or steel, small copper inserts called sekigane (責金) are often used to prevent contact between the blade and the tsuba.
This photo essay will attempt to portray a simple approach to creating this type of guard using basic tools and techniques, with a focus on the installation of sekigane. The tools used in this example are a charcoal forge, hammers, pliers, chisels, drill, wire cutter, hacksaw, and files.
Wrought iron is a fairly pure form of iron which was manufactured for all structural and utilitarian applications prior to the modern production of mild steel. It is usually easy to identify in the wild by the way it corrodes into a wood grain like appearance rather than the moon-textured look of corroded steel.
A simple test for wrought iron is to cut partway through a bar and then break off the rest. It will bend and then finally break, revealing stringy iron fibers rather than the homogeneous matte-gray internal structure of modern steel. The linear striations are caused by the residual slag left between layers during smelting and refining and are often appreciated as an aesthetic point in artistic works.
A beautiful example of the linear wood grain appearance of the surface of highly corroded wrought iron.
By contrast, highly corroded steel exhibits a pitted or cratered surface pattern.
Positive results of a break test for wrought iron (in some cases this test might also indicate annealed or mid to low carbon shear steel). Note the stringy, layered structures that are revealed as the ductile iron fibers bend and eventually give way.
Forging the Tsuba
Forging wrought iron should be done at a much higher temperature than high carbon or even mild steel. At lower temperatures there is an increased risk of cracking along the slag lines whereas higher temperatures ensure that everything is in a malleable state. Punching and drifting must be done with care and at very high heat, resist the urge to keep forging into the lower range as it cools. Because wrought iron contains no carbon it can be safely heated to a bright yellow or almost white heat without burning up. In terms of planning and shaping, the grain direction of the layers must be considered, almost as if working with wood.
Forging a sea-salvaged rod into a tsuba blank to accommodate the size of the soapstone pattern. Note the visible temperature difference along one edge that indicates a split has partially separated a strip. Hot punching (or drilling and cold chiselling) and filing to open the nakago-ana slightly larger than the tang.
Filing to check the flatness and inspect the surface. Next the surface is oxidized using high heat and an oxygen-rich charcoal forge blast, periodically dipping quickly into water and wire brushing the surface. This weathering process is known as yakite or yakinamashi.
Making the Sekigane
After yakite/yakinamashi, the notches are filed and then chamfered for the sekigane.
Reclaimed copper lightning rod is cut to length for the plugs, estimating the approximate volume required for each.
The thick wire is cold forged into rectangular billets that just fit into the notches, and then tapped into place. Very thin needle-nosed pliers are used to hold and stabilize the small pieces on the anvil during forging.
Turning the piece over frequently and working from both sides, the plugs are expanded to fill the chamfers that lock them in place. A smaller and slightly rounded hammer is used for the final work.
The goal is to have estimated the volume of copper so that when fully forged down they fill all gaps and lay flush or below the surface of the tsuba. If they protrude, some trimming with a small tagane cold chisel will be necessary.
The sekigane can now be filed out close to the original tang profile in preparation for fitting. A small needle file is helpful for this stage. The sekigane should be the only contact points on the tang.
If the blade is polished the sekigane can be filled to final fit, but if the blade is unfinished some extra copper should be left until later to prevent a loose fit.
Finishing the Tsuba
The excess iron is cut away using a hack saw. Note that this is not a common historical pattern tanto tsuba but a fusion style piece with western proportions.
Filing the edges prepares the piece for finishing. Note that to employ the benefits of yakite/yakinamashi on the rim and expose tekkotsu (iron bones), the shape should be cut and filed before filing in the notches for sekigane.
Soaking for several hours in a vinegar and water solution dissolves the scale and surface slag, highlighting the organic wood grain structure of the metal. Note that if a rust patina is desired, the copper sekigane should be inserted at the very end, after the patina is achieved.
Read more about the making of this piece here: Touzai Tanto
