~Blacksmithing~

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BLACKSMITHING

The process of blacksmithing (from Wikipedia)

Blacksmiths work with "black" metals, especially iron. The black color comes from a layer of oxides that form on the surface of the metal during heating (called fire scale).The term "smith" originates from the word "smite", which means to hit. Thus, a blacksmith is a person who smites the black metals.Blacksmiths work by heating pieces of wrought iron or steel in a forge until the metal becomes soft enough to be shaped with tools such as a hammer. Heating is accomplished by the use of a forge fueled by propane, natural gas, coal, charcoal, or coke.Modern blacksmiths may also employ an oxyacetylene or similar blowtorch for more localized heating. Color is important for indicating the temperature and workability of the metal: As iron is heated to increasing temperatures, it first glows red, then orange, yellow and finally white. The ideal heat for most forging is the yellow-orange color appropriately known as a "forging heat." Because they must be able to see the glowing color of the metal, many blacksmiths work in dim, low-light conditions.The techniques of blacksmithing may be roughly divided into forging (sometimes called "sculpting"), welding, heat treating and finishing.

Forging

Forging is also referred to as sculpting because it is the process of shaping metal. Forging is different from machining in that material is not removed by these processes (with the exception of punching and cutting), rather the iron is hammered into shape There are five basic operations or techniques employed in forging: drawing, shrinking, bending, upsetting and punching.These operations generally employ hammer and anvil at a minimum, but smiths will also make use of other tools and techniques to accommodate odd sized or repetitive jobs.Forging is the working of metal by plastic deformation. It is distinguished from machining, the shaping of metal by removing material, such as by drilling, sawing, milling, turning or grinding, and from casting, wherein metal in its molten state is poured into a mold, whose form it retains on solidifying. The processes of raising, sinking, rolling, swaging, drawing and upsetting are essentially forging operations although they are not commonly so called because of the special techniques and tooling they require.Forging results in metal that is stronger than cast or machined metal parts. This is because during forging the metal's grain flow changes into the shape of the part, making it stronger. Some modern parts require a specific grain flow to ensure the strength and reliability of the part.Many metals are forged cold, but iron and its alloys are almost always forged hot. This is for two reasons: first, if work hardening were allowed to progress, hard materials such as iron and steel would become extremely difficult to work with; secondly, most steel alloys can be hardened by heat treatments, such as by the formation of martensite, rather than cold forging. Alloys that are amenable to precipitation hardening, such as most structural alloys of aluminium and titanium, can also be forged hot, then made strong once they achieve their final shape. Other materials must be strengthened by the forging process itself.Forging was done historically by a smith using hammer and anvil, and though the use of water power in the production and working of iron dates to the 12th century CE, the hammer and anvil are not obsolete. The smithy has evolved over centuries to the forge shop with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry.In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers are large, having reciprocating weights in the thousands of pounds. Smaller power hammers, 500 pounds or less reciprocating weight, and hydraulic presses are common in art smithies as well. Steam hammers are becoming obsolete.In industry a distinction is made between open- and closed-die forging. In open-die work the metal is free to move except where contacted by the hammer, anvil, or other (often hand-held) tooling. In closed-die work the material is placed in a die resembling a mold, which it is forced to fill by the application of pressure. Many common objects, like wrenches and crankshafts, are produced by closed-die forging, which is well suited to mass production. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work.Closed-die forging is more expensive for mass production than is casting, but produces a much stronger part, and is used for tools, high strength machine parts and the like. Forgings are commonly used in automotive applications, where high strength is demanded, with a constraint on the mass of the part (high strength-to-mass ratio). Forged parts are more suitable for mass production. The process of forging a part becomes cheaper with higher volumes. For these reasons forgings are used in the automotive industry, usually after some machining. One particular variant, drop forging, is often used to mass produce flat wrenches and other household tools.

Types of forges

 Coal/coke/charcoal forge

 

Standard coal forge

A forge which typically uses bituminous coal, industrial coke or charcoal as the fuel to heat metal. The designs of these forges have varied over time, but whether the fuel is coal, coke or charcoal the basic design has remained the same.A forge of this type is essentially a hearth or fireplace designed to allow a fire to be controlled such that metal introduced to the fire may be brought to a malleable state or to bring about other metallurgical effects (hardening, annealing, and drawing temper as examples). The forge fire in this type of forge is controlled in three ways: 1) amount of air, 2) volume of fuel, and 3) shape of the fuel/fire.

Over thousands of years of forging, these devices have evolved in one form or another as the essential features of this type of forge:

bullet Tuyere -- a pipe through which air can be forced into the fire
bullet Bellows or blower -- a means for forcing air into the tuyere
bullet Firepot or hearth -- a place where the burning fuel can be contained over or against the tuyere opening.

During operation, fuel is placed in or on the hearth and ignited. A source of moving air, such as a fan or bellows, introduces additional air into the fire through the tuyere. With additional air, the fire consumes more fuel and burns hotter.A blacksmith balances the fuel and air in the fire to suit particular kinds of work. Often this involves adjusting and maintaining the shape of the fire.In a typical, but by no means universal, coal forge, a firepot will be centered in a flat hearth. The tuyere will enter the firepot at the bottom. In operation, the hot core of the fire will be a ball of burning coke in and above the firepot. The heart of the fire will be surrounded by a layer of hot but not burning coke. Around the unburnt coke will be a transitional layer of coal being transformed into coke by the heat of the fire. Surrounding all is a ring or horseshoe-shaped layer of raw coal, usually kept damp and tightly packed to maintain the shape of the fire's heart and to keep the coal from burning directly so that it "cooks" into coke first.If a larger fire is necessary, the smith increases the air flowing into the fire as well as feed and deepen the coke heart. The smith can also adjust the length and width of the fire in such a forge to accommodate different shapes of work.The major variation from the forge and fire just described is a 'back draft' where there is no fire pot, and the tuyere enters the hearth horizontally from the back wall.Coke and charcoal may be burned in the same forges that use coal, but since there is no need to convert the raw fuel at the heart of the fire (as with coal), the fire is handled differently.Individual smiths and specialized applications have fostered development of a variety of forges of this type, from the coal forge described above, to simpler constructions amounting to a hole in the ground with a pipe leading into it.

Gas forge

A forge typically uses propane or natural gas as the fuel. One common, efficient design uses a cylindrical forge chamber and a burner tube mounted at a right angle to the body. The chamber is typically lined with refractory materials, preferably a hard castable refractory ceramic. The burner mixes fuel and air which are ignited at the tip, which protrudes a short way into the chamber lining. The air pressure, and therefore heat, can be increased with a mechanical blower or by taking advantage of the Venturi effect.Gas forges vary in size and construction, from large forges using a big burner with a blower or several atmospheric burners to forges built out of a coffee can utilizing a cheap, simple propane torch. A small forge can even be carved out of a single soft firebrick.The primary advantage of a gas forge is ease of use, particularly for a novice. A gas forge is simple to operate compared to coal forges, and the fire produced is clean and consistent. They are less versatile, as the fire cannot be reshaped to accommodate large or unusually shaped pieces;. It is also difficult to heat a small section of a piece. A common misconception is that gas forges cannot produce enough heat to enable forge-welding, but a well designed gas forge is hot enough for any task.

Drop forge

The workpiece, say a wrench, is created by hammering a piece of hot metal into an appropriately shaped die. The metal (in an easily produced shape like a rod or brick) is heated and placed on the bottom part of a die. The top part of the die then drops onto the piece, which gives the forge its name. The die may drop under gravity or be powered, but in all cases drop forging involves impact. The force of the impact causes the heated metal to flow into the shape of the die, with some metal squirting out of the thin seams between the dies. This thin metal is called "flash" and is cut away in the next stage of processing. The drop-forged pieces usually need further processing, like machining and polishing of working surfaces, to provide tighter tolerances than forging alone can provide, and to produce a good finish.

Hydraulic press forge

In hydraulic press forging the work piece is pressed between the two die halves with gradually increasing force, over a period of a few seconds. The quality of the pieces is better than drop forging as there is more control over metal flow, but takes longer and requires more energy. It also makes the same shape continuously.

Hot forging

Forging is the hammering or forming of hot or cold metal into a certain shape. When the hammering and forming is done by hand it is called hand forging and when it is done by machine it is called drop forging. The forging process starts after having brought the steel to the correct workable temperature between 900°C and 1100°. It allows us, through a process of reduction (for crushing), to get the most various shapes.

Finery forge

A finery forge was a water-powered mill, where pig iron was refined to produce bar iron.
 

Forging Equipment

 Anvil

The anvil serves as a work bench to the blacksmith, where the metal to be beaten is placed. An anvil body is made of mild steel, with a top face of high carbon steel approximately 20mm thick welded on it. The flat top has two holes; the wider is called the hardy hole, where the square shank of the hardy fits. The smaller hole is called the punch hole, used as clearance when punching holes in hot metal.

 Chisel

Chisels are made of high carbon steel whose cross-section is an octagon. They are hardened and tempered at the cutting edge while the head is left soft so it will not crack when hammered. Chisels are of two types, the hot and cold chisels. The cold chisel is used for cutting cold metals while the hot chisel is for hot metals. Usually the hot chisels are thinner and therefore can not be substituted with the cold chisel.

 Tongs

Tongs are used by the blacksmith for holding hot metals securely. The mouths are made in various shapes to suit the gripping of various shapes of metal.

Fuller

Fullers are forming tools of different shapes used in making grooves or hollows. They are often used in pairs, the bottom fuller has a square shank which fits into the hardy hole in the anvil while the top fuller has a handle. The work is placed on the bottom fuller and the top is placed on the work and struck with a hammer. The top fuller is also used for finishing round corners and for stretching or spreading metal.

Hardy

The hardy is a cutting tool similar to the chisel. It is used as a chisel or hammer for cutting both hot and cold metals. It has a square shank that fits into the hardy hole in the anvil, with the cutting edge facing upwards. The metal to be cut is placed on the cutting edge and struck with a hammer.

Drawing

Drawing lengthens the metal by reducing one or both of the other two dimensions. As the depth is reduced, the width narrowed, or both the piece is lengthened or "drawn out".
As an example of drawing, a smith making a wood chisel might flatten a square bar of steel, lengthening the metal, reducing its depth but keeping its width consistent.
Drawing does not have to be uniform. A taper can result as in making a wedge or the woodworking chisel blade. If tapered in two dimensions a point results.
Drawing can be accomplished with a variety of tools and methods. Two typical methods using only hammer and anvil would be: hammering on the anvil horn, and hammering on the anvil face using the cross peen of a hammer.
Another method for drawing is to use a tool called a fuller, or the peen of the hammer to hasten the drawing out of a thick piece of metal. The technique is called fullering from the tool. Fullering consists of hammering a series of indentations (with corresponding ridges) perpendicular to the long section of the piece being drawn. The resulting effect will be to look somewhat like waves along the top of the piece. Then the hammer is turned over to use the flat face and the tops of the ridges are hammered down level with the bottoms of the indentations. This forces the metal to grow in length (and width if left unchecked) much faster than just hammering with the flat face of the hammer.

Upsetting

Upsetting is the process of thickening the metal by reducing one dimension and increasing another. It can be described as pushing the metal back into itself to thicken it. For example in preparation for making a bolt head, a smith will hammer the end of a rod, thickening the end of the rod and shortening its overall length. The heated end of the rod is placed pointing down on an anvil. The cool end is then struck repeatedly, which produces a bulge at the hot end of the metal.

Shrinking

Shrinking, while similar to upsetting, is essentially the opposite process as drawing. As the edge of a flat piece is curved such as in the making of a bowl shape, the edge will become wavy as the material bunches up in a shorter radius. At this point the wavy portion is heated and the waves are gently pounded flat to conform to the desired shape. If you were to compare the edge of the new shape to the original piece, you would discover that the material is thicker than before. This is due to the excess material that formed the waves being pushed into a uniform edge that has a smaller radius than before.

 Bending

Bending at its simplest is simply that: bending the metal to a particular shape. Hooks are made this way, as well as loops and chain links from rod.
Bending can be done with the hammer and anvil although blacksmiths tend to make jigs and specialized tools to make the process easier and more consistent. With a hammer and anvil a bend is made by laying the heated metal on the anvil with part of the stock extending over the edge. The unsupported stock is struck with the hammer forcing it downward. Once the bend is started it might be continued on the face of the anvil with the end of the bend turned up: striking the outside of the bend will make it tighter and on the inside will open it. The bend might be refined by bracing the stock against the horn or the face and side of the anvil and striking the stock against these forms.

Punching

Punching makes a depression or hole in the metal by driving a punch into or through the metal. Punching may be done to create a decorative pattern, or to make a hole. For example, in preparation for making a hammer head, a smith would punch a hole in a heavy bar or rod for the hammer handle. Punching is not limited to depressions and holes. It also includes cutting, or slitting and drifting.

Combining Processes

The five basic processes are often combined to produce and refine the shapes necessary for finished products. For example to fashion a cross peen hammer head a smith would start with a bar roughly the diameter of the hammer face, the handle hole would be punched and drifted, the head would be cut (punched, but with a wedge), the peen would be drawn to a wedge, and the face would be dressed by upsetting.In the example of making a chisel, as it lengthened by drawing it would also tend to spread in width, so a smith would frequently turn the chisel-to-be on its side and hammer it back down -- upsetting it -- to check the spread and keep the metal at the correct width for the project.As another example, if a smith needed to put a 90 degree bend in a bar and wanted a sharp corner on the outside of the bend, the smith would begin by hammering an unsupported end to make the curved bend. Then, to "fatten up" the outside radius of the bend, one or both arms of the bend would need to be pushed back into the bend to fill the outer radius of the curve. So the smith would hammer the ends of the stock down into the bend, 'upsetting' it at the point of the bend. The smith would then dress the bend by drawing the sides of the bend to keep it the correct thickness. The hammering would continue -- upsetting and then drawing -- until the curve had been properly shaped. In this case the primary operation was the bend, but the drawing and upsetting are done to refine the shape.

Welding

Welding is the joining of metal of the same or similar kind such that there is no joint or seam: the pieces to be welded become a single piece.A modern blacksmith has a range of options and tools to accomplish this. The basic types of welding commonly employed in a modern shop include traditional forge welding as well as modern methods, including oxyacetylene and arc welding.In forge welding the pieces to be welded are heated to what is generally referred to as "welding heat". For mild steel most smiths judge this temperature by color: the metal will glow an intense yellow or white. At this temperature the steel is near molten .Any foreign material in the weld, such as the oxides or "scale" that typically form in the fire, can weaken it and potentially cause it to fail. Thus the mating surfaces to be joined must be kept clean. To this end a smith will make sure the fire is a reducing fire: a fire where at the heart there is a great deal of heat and very little oxygen. The smith will also carefully shape the mating faces so that as they are brought together foreign material is squeezed out as the metal is joined. To clean the faces, protect them from oxidation, and provide a medium to carry foreign material out of the weld the smith will use flux -- typically powdered borax, silica sand, or both.The smith will first clean the parts to be joined with a wire brush, then put them in the fire to heat. With a mix of drawing and upsetting the faces will be shaped so that when finally brought together the center of the weld will connect first and the connection spread outward under the hammer blows, pushing the flux and foreign material out.The dressed metal goes back in the fire, is brought near to welding heat, removed from the fire, brushed, flux is applied, and it is returned to the fire. The smith now watches carefully to avoid overheating the metal. There is some challenge to this, because in order to see the color of the metal it must be removed from the fire, and this exposes the metal to air, which can cause it to oxidize rapidly. So the smith might probe into the fire with a bit of steel wire, prodding lightly at the mating faces. When the end of the wire sticks the metal is at the right temperature (a small weld has formed where the wire touches the mating face so it sticks).Now the smith moves with rapid purpose. The metal is taken from the fire and quickly brought to the anvil, the mating faces are brought together, the hammer lightly applying a few taps to bring the mating faces into complete contact and squeeze out the flux, and finally returned to the fire again.The weld was begun with the taps, but often the joint is weak and incomplete, so the smith will again heat the joint to welding temperature and work the weld with light blows to "set" the weld and finally to dress it to the desired shape.

Heat treatment

Other than to increase its malleability, another reason for heating the metal is for heat treatment purposes. The metal can be hardened, tempered, normalized, annealed, case hardened, and subjected to other processes that change the crystalline structure of the steel to give it specific characteristics required for different uses. Only steel, not iron, can be heat treated, and generally speaking, the higher the carbon content of the steel, the more it can be hardened.When working with steels, a blacksmith will heat the metal and then quench it in various liquids such as water or oil. The purpose of quenching is to produce rapid cooling to generate specific microstructures in the metal. A quench from a bright red or orange heat generally results in steel that is hard and brittle, so a second process, called tempering, is usually done to increase the toughness of the piece and reduce its hardness.Tempering involves heating the material to a specific temperature (lower than red heat) usually called "critical temperature" and judged for common steel by the temperature at which the metal loses its magnetic attraction. Sometimes it is quenched again after this heating.With most tool steels, the degree of temper achieved can be gauged by the appearance of a colored oxidation tint on the metal surface. Different uses require different hardness and toughness combinations, and so receive different degrees of temper. It is possible to temper different parts of an object to different levels of hardness, which is one area where the skill of the blacksmith comes into play.For example, the face of a hammer is often made harder than the main body, giving a blend of a hard wearing face with a resilient and tough head. Edged weapons, in particular, are often treated to provide a hard edge (which will retain sharpness with use longer) while keeping the main body of the blade tough to be more flexible and resist breaking from a powerful or jarring blow.

Finishing

Depending on the intended use of the piece a blacksmith may finish it in a number of ways:

bullet A simple jig that the smith might only use a few times in the shop it may get the minimum of finishing: a rap on the anvil to break off scale and a brushing with a wire brush.
bullet Files can be employed to bring a piece to final shape, remove burrs and sharp edges, and smooth the surface.
bullet The wire brush either as a hand tool or power tool can further smooth and brighten a surface.
bullet Grinding stones, abrasive paper, and emery wheels can further shape, smooth and polish the surface.
bullet There are a range of treatments and finishes to inhibit oxidation of the metal and enhance or change the appearance of the piece. An experienced smith selects the finish based on the metal and intended use of the item.
bullet Finishes include but are not limited to: paint, varnish, blueing, browning, oil, and wax.

The blacksmith's materials

When iron ore is smelted into usable metal, a certain amount of carbon is usually alloyed with the iron. The amount of carbon has extreme effects on the properties of the metal. If the carbon content is over 2%, the metal is called cast iron. Cast iron is so called because it has a relatively low melting point and is easily cast. It is quite brittle however, and therefore not used for blacksmithing. If the carbon content is between .25% and 2%, the resulting metal is tool steel, which can be heat treated as discussed above. When the carbon content is below .25%, the metal is either "wrought iron" or "mild steel." The terms are never interchangeable. In pre-industrial times, the material of choice for blacksmiths was wrought iron. This iron had a very low carbon content, and also included up to 5% of glassy slag. This slag content made the iron very tough, gave it considerable resistance to rusting, and allowed it to be more easily "forge welded," a process in which the blacksmith permanently joins two pieces of iron, or a piece of iron and a piece of steel, by heating them nearly to a white heat and hammering them together. Forge welding is more difficult to do with modern mild steel. Modern steel production, using the blast furnace, cannot produce true wrought iron, so this material is now a difficult-to-find specialty product. Modern blacksmiths generally substitute mild steel for making objects that were traditionally of wrought iron.

The Blacksmith's Tools

Over the centuries blacksmiths have taken no little pride in the fact that theirs is one of the few crafts that allows them to make the tools that are used for their craft. Time and tradition have provided some fairly standard basic tools which vary only in detail around the world."All a smith needs is something to heat the metal, something to hit the metal on and something to hit the metal with."The forge is the fireplace of a blacksmith's shop. It provides the means to keep the fire contained and controlled.The anvil at its simplest is a large block of iron or steel. Over time this has been refined to provide a rounded horn to facilitate drawing and bending, a face for drawing and upsetting and bending, and one or more holes to hold special tools (swages or hardies) and facilitate punching. Often the flat surface of an anvil will be hardened steel, and the body made from tougher iron.Blacksmiths' hammers tend to have one face and a peen. The peen is typically either a ball or a blunt wedge (cross or straight peen depending on the orientation of the wedge to the handle) and is used when drawing.While a great deal of work may be done with those three basic tools blacksmiths tend to augment their tools with some of the following, depending on the kinds of work they do.Tongs are used to hold the hot metal. They come in a range of shapes and sizes.

 

Swage. The block is quite deep.

Swages (hardies) and fullers are shaping tools. Swages are either stand alone tools or fit the "hardie hole" on the face of the anvil. The metal is shaped by being driven into the form of the swage. Opposite to the swage in some respects is the fuller which may take a number of shapes and is driven into the metal with a hammer. Swages and fullers are often paired to bring a piece of metal to shape in a single operation, essentially a set of dies. A fuller and swage pair might be spoon shaped, for example, the swage dished to form the bowl and the fuller the convex mirror of the swage. Together they will quickly stamp a spoon shape on the end of a bar.There are many other tools used by smiths, so many that even a brief description of the types is beyond the scope of this article and the task is complicated by a variety of names for the same type of tool. Further complicating the task is that making tools is inherently part of the smith's craft and many custom tools are made by individual smiths to suit particular tasks and the smith's inclination. In the late 1930s Alexander G. Weygers (a sculptor, painter, and smith} published The Complete Modern Blacksmith, in which he provided instructions for creating many useful tools for a blacksmith, which was followed in 1979 by The Making of Tools.With that caveat one category of tools should be mentioned: jigs. A jig is generally a custom built tool, usually made by the smith, to perform a particular operation for a particular task or project. For example, a smith making decorative scrolls for an iron fence will make a bending jig, or scroll iron, to apply a particular shape to the stock, ensuring that each scroll has the same bend. (To estimate the length of stock required to form a scroll of any given size and number of turns the Clackson scroll formula is used.)

History and the present

Prior to the industrial revolution, a "village smithy" was a staple of every town. Mass production techniques have reduced the marketplace for blacksmith work except in Africa, India, Southeast Asia, and South America where large numbers of artisans continue to do traditional work. In more industrialized regions, an increasing demand for custom metalwork has given rise to a new breed of smiths commonly known as Artist-Blacksmiths. In recent years the forging of stainless steel has given rise to a fresh approach to architectural blacksmithing. Blacksmith tools are no longer used in war but is rather a decorative weapon or used by collectors.

One famous blacksmith, albeit a mythical one, was Hephaestus (Latin: Vulcan). He was the blacksmith of the gods in Greek and Roman mythology. A supremely skilled artisan whose forge was a volcano, he constructed most of the weapons of the gods, and was himself the god of fire and metalworking.