Historically, has been the work of specialized smiths or metalworkers called armorers or swordsmiths. Modern armorers and swordsmiths still ply their trade although to a more limited clientele. Their products are oriented toward collectors, those who pursue various traditional martial arts, enactors, and as props for film and theater. Some modern smiths also make swords and smaller blades for the technical challenge they present. Swords have been made of many different materials over the centuries and with a variety of tools and techniques. Much of the value of a sword is less the material and more the effort, skill and experience that go into making a sword. A good sword is more than a piece of metal shaped to a long tapered form and fitted with a handle, although certainly many swords that are little more than that have been used over the millennia.
While there are many criteria for evaluating a sword, generally the three key criteria are hardness, strength and balance. A good sword has to be hard enough to hold an edge along a length which can range from 18 inches (45 cm) to more than 36 inches (90 cm) and at the same time it must be strong enough and flexible enough that it can absorb massive shocks at just about any point along its length and not crack or break.
Finally it should be balanced along its length so that it can be easily wielded. The challenge and mystique of swords and their fabrication comes in large measure from how crafts people over the millennia have responded to the problems created by the interplay of the three factors just described: harmonizing hardness, strength and balance.
A quality sword cannot be quickly made either, and later steps in their fabrication can reveal flaws and mistakes ruining a great deal of time and effort, therefore a good quality sword represents the skilled time and efforts of one or more crafts people, crafts people who executed every small step of the process flawlessly or nearly so to create that weapon. Sword fabrication breaks down into roughly three processes: forming, heat treating and finishing. Depending on many factors such as base materials, location and era these processes might merge, overlap or be dispensed with entirely. For example, an iron short sword from the early Iron Age might be formed by forging, normalized to remove stresses in the material from the forging, and simply finished by grinding and affixing the simplest of handles to it eliminating the hardening process and greatly simplifying the finishing. As a contrasting example, the sword of a Japanese Daimyo from the 1500s would likely go through a more involved forging process, welding together different types of steel, or steel and iron; and then forging them to shape. The resulting, relatively soft, blade might then go through the first phase of finishing — filing, grinding, rough polishing — before heat treating.
Once hardened and tempered the blade would go into a second phase of finishing polishing, sharpening and fitting it with an elaborate guard, sheath and handle. Likewise, a knightly sword of the 12th century would undergo pattern-welding of various grades of iron and crucible steel and be eventually built by laminating different types of steel together to produce a blade which is simultaneously hard and tenuous. The first example might be accomplished in a few hours by a smith. The latter would require weeks or months and the involvement of perhaps three or four artisans from as many specialized crafts. Swords can be shaped by a variety of metalworking techniques. In some times and places one technique has been used exclusively, in others combinations have been applied. The primary techniques are forging and stock removal. Stock removal shapes the sword from prepared stock that is larger in all dimensions than the finished sword by filing, grinding and cutting.
While the technique has been available for centuries it was not widely used for making swords until the 19th or 20th century as it is wasteful of the raw material. Where iron and steel are plentiful this method is frequently used as it requires less skill and time. In places and times where iron and steel have been more rare and valuable stock removal has not been used except as part of the finishing process. Forging uses heat to bring the material to a malleable state. The material is then hammered to shape, typically using hammer and anvil together with specialized set and fuller tools depending on the particular technique. There are a variety of forging techniques for sword making and many variations upon those. The techniques employed in different places and times tend to affect the style of the resulting blades. Much of the development and selection of techniques has been driven by the type and availability of raw materials. Broadly speaking, if metal supply is limited blades have tended to be smaller. Similarly when the supply of steel has been limited, techniques for building up the basic billet from which a sword would be forged by welding together iron and steel or different types and grades of steel were developed.
Our modern knowledge of historical techniques is limited in some ways. Historically sword fabrication has been, effectively, high military technology, therefore, just as the techniques of producing modern weapons are often closely guarded, the techniques developed for creating superior swords were also guarded and rarely, if ever, published. In most techniques the basic materials, generally iron and/or steel, are shaped into a bar or billet first. At this stage if several metals are to be used they will be combined by welding to form the billet. In some techniques, notably the traditional folded steel blades of Japan, the billet might be drawn, folded and welded back on itself creating layers of steel of different types. In others longer bars or rods of steel and iron might be welded together, edge to edge, to create the basic billet placing the softer iron inside with the steel at the core and edges. Once the billet is created it is drawn out farther, generally tapering to the edge(s) and point. A technique called fullering would be used to create the tang, a section of the sword body with reduced dimensions where the handle is attached. The same technique might be used to create a ridge or ridges down the length of the blade. Whether single or multiple, the ridge’s primary purpose to give the blade greater structural strength relative to its mass.
The final step of forming, and one that affects both the finishing and the heat treatment is ‘normalizing’. The blade would be carefully and evenly heated and then cooled slowly. The point of normalizing is to remove the stresses which may have built up within the body of the blade while it was being forged. During the forging process the blade might be heated and cooled differentially creating stress, some parts might be hammered more than others, some areas hammered enough to “work harden”. If these stresses are left in the blade they could affect the finishing and when it came time to heat treat the blade, the hardening and tempering might not be as even. Potentially enough stress could be added that the blade would be weak in spots, weak enough that it could fail under enough strain. Heat treating, encompasses several processes including annealing, normalizing, hardening and tempering. Often the process is called “tempering” but that process refers to just one of the several processes. A detailed discussion of heat treating is not germane to this article. Those who are interested are encouraged to follow the link to the heat treatment article and explore that article and its related topics. Until the advent of new steel alloys over the last century most tools and weapons of steel, iron, bronze or even copper were heat treated at one or more stages of their fabrication. Simply put the processes of heat treating soften or harden metal.
During fabrication the metal might be softened to relieve stresses built up from forging and differential heating, and to make the metal easier to file, engrave or polish. As one of the last processes in fabrication the blade would be hardened and if the sword was made of steel in whole or part it would then be tempered making the blade less brittle and more springy. After the discovery of iron, it quickly became apparent that iron blades were too soft to hold an edge properly. This led to quenching, which involved reheating the treated iron and then plunging it into a quenchant, such as water. The heating of the metal forces the usually crystalline lattice of molecules to become more fluid, and the quenching then forces them back into a crystalline configuration. Because of this rapid cooling, the reformed crystals tend to be smaller, inhibiting the movement of the molecules in relation to each other, thus greatly increasing the hardness of the metal. Hardening the metal lets the metal hold shape better and therefore hold an edge longer but hardness is at the cost of brittleness. Given the intended use of a sword the blade must be strong as well, so the hardness is eased or tempered in the case of steel blades to give the blade strength and flexibility as well.
Hardening and tempering of any blade, knife or sword, is challenging. With swords, due to their length, the challenge is greater as in a typical quenching it is possible to bend or warp the blade if it is not introduced to the quenchant smoothly and evenly. Given the greater length of a sword over a knife there are more opportunities for errors, flaws and mistakes to accumulate. Further there is a great deal of art and craft in arriving at a balance of hardness and strength and creating blades which consistently deliver both. Pre-Iron Age swords of bronze were also, likely, heat treated. Most likely they were annealed one or more times in the fabrication process and the edges were intentionally work hardened. Swords could also be differentially hardened so that some parts, like the cutting edge, are harder than the body. Finishing a sword encompasses bringing the blade to final shape and polish; decorating the sword; and crafting and assembling the hilt, guard and sheath. The swordsmith would be most concerned with the state of the blade itself and possibly decorating the blade and preparing the guards and pommel if any. Other artisans would likely be involved in the work of fashioning the hilt, sheath and other furniture; and in any fine decoration.
Once the blade had been heat treated, a sword would be ground with progressively finer abrasives until the desired finish was achieved. It would then be sharpened. Some pursue the traditional methods while others apply modern tools, techniques and materials to the craft. Individuals around the world continue to use traditional methods to make swords to keep the craft and techniques alive. The vast majority of commercially available swords have been made with modern tools and materials as it is simply not cost effective to hand forge a sword. Most commercially available swords have been manufactured by stock removal.