Blacksmithing Secrets Part 1
Forging, Tempering, and Welding
The material in this article originally appeared in ‘Shopwork on the Farm’, a textbook by Mack M. Jones, copyright 1945, McGraw-Hill.
With each new wave of uncertainty, and with each new out-migration to the countryside, there is renewed thirst for information on basic crafts and skills, information which may help to grant the individual and the family an increased measure of self-sufficiency. Blacksmithing, that ages old art of heating and shaping and welding metals, slips in and out of favor as a craft to learn. Today, in our time of wire-feed arc welders and fancy tools, there are many who see this skill as completely obsolete. And then there are the rest of us who take infinite pleasure and comfort in being able to start a fire in our forge, heat a piece of steel, and shape it by hammer blows.There are those of us who know that this craft will always have practitioners who treasure the Blacksmith’s Secrets. LRM
Whether a farmer can afford a forge and anvil will depend upon the distance to a blacksmith shop, the amount of forging and other smithing work he needs to have done, and his ability as a mechanic. Although not every farmer can profitably own blacksmithing equipment, many farmers can. If a farmer cannot, he should remember that a great variety of repairs can be made with the use of only a few simple cold-metal working tools.
Although blacksmithing is generally more difficult than woodwork, most farm boys with average mechanical ability can soon learn to do simple blacksmithing and will feel well repaid for their efforts. In all mechanical work, much more rapid and satisfactory progress can be made by a study of theory and principles along with practice. This is particularly true of blacksmithing.
Selecting Forging Equipment for the Shop
The Forge. The forge for the farm shop should have a gear-driven blower operated by a crank, and it should have a hearth at least 18 in. wide, preferably somewhat larger. A good way of providing a good forge is to get a good blower and make a hearth or stand of concrete or brick, or of pipe or angle iron. A plate with holes drilled in it can be mounted in the bottom of the hearth for admitting the air blast. The forge should have a hood and smoke pipe for taking away the smoke.
The Anvil. Anvils are of two general kinds: cast iron and steel. Steel anvils are much better and should be used if they can be afforded. The two kinds can be readily distinguished by striking with a hammer. A cast anvil has a dead sound, while a steel one has a clear ring.
Anvils are commonly available in sizes ranging from 50 to 200 lb. An anvil weighing 100 or 125 lb. is quite satisfactory for the farm shop.
A piece of railroad iron or rail 24 to 30 in. long and mounted on a block or stand makes a good anvil for light hammering and riveting, although a much greater variety of work can be done on a regular anvil.
Place the anvil on a substantial mounting, preferably of wood. Locate it in front of the forge, so that the workman can take irons from the fire and place them on the anvil by simply making a short turn and without the necessity of taking even a full step. Place the horn of the anvil to the left for a right-handed workman and to the right for a left-handed man. Mount the anvil at such a height that the top can be just touched with the knuckles of the clenched fist when standing erect and swinging the arm straight down (see Fig. 427).
Tongs. A few pairs of tongs of different sizes and kinds should be provided for the farm shop. Various types are available, the most common ones being flat-jawed tongs and hollow-bit curved-lip tongs (see Fig. 428). The hollow-bit curved-lip bolt tongs are probably best for general work. They can hold flat bars as well as round rods and bolts, and the curved part back of the tip makes it possible to reshape them easily to fit various sizes of stock. By filing or grinding a groove crosswise in the end of each lip, they can be made to hold links and rings practically as well as special link tongs. Tongs 18 to 20 in. long are a good size for average work.
Hammers. A blacksmith’s hand hammer weighing 1 1/2 or 2 lb. And another weighing 3 or 3 1/2 lb. will handle all ordinary work very satisfactorily.
Hardy, Chisels, Punches. There should be at least one hardy of a size to fit the hole in the anvil, and it may be advisable to have two, one that is thin and keen for cutting hot metal, and one that is thick, heavy, and tempered for cutting cold metal. It is a good plan to have a fair assortment of various sizes of chisels and punches. These can be made easily in the shop. If considerable blacksmithing is to be done, it would be well to have a hot cutter and a cold cutter (simply large chisels with handles on them) for heavy cutting with a sledge hammer. It would be well also to have one or two large punches with handles on them for punching holes in hot metal. Punches for making holes 3/8 in. and 1/2 in. in diameter are probably most useful.
Vise. One vise can well serve for all metalwork in the farm shop, including blacksmithing if it is heavy and strong. A blacksmith’s steel leg vise with jaws 4 to 5 in. wide is generally preferred as an all-purpose metalworking vise. A leg vise is one that has one leg extending down to be anchored or fastened into the floor (see Fig. 429). Such a vise can be used for heavy hammering and bending better than other types. If there is a strong steel mechanist’s vise in the shop, it can be used for blacksmithing work if care is used not to do too heavy hammering or bending with it.
Fire Tools. A small shovel and poker or rake will be needed for use on the forge fire. These can easily be made in the shop. A flat piece of heavy sheet iron about 3 or 4 in. wide by 4 or 5 in. long, riveted to a bar or rod for a handle, makes a good shovel (see Fig. 430A). A 1/2-in. round rod, with an oblong eye in one end to serve as a handle and the other end flattened and curved, makes a good combination poker and rake (see Fig. 430B).
Measuring Tools. Some kind of metal rule will be needed for measuring and checking pieces being forged. A small steel square is very good for both measuring lengths and checking angles and bends. A caliper rule (see Fig. 431B) for measuring the diameter of rods and thickness of parts, although not a necessity, will be found convenient.
Building and Maintaining a Forge Fire
A good fire is the first requirement for good blacksmithing. Many beginners do poor work simply because they do not know the importance of a good fire. Two students sometimes attempt to use the same fire. This is usually a waste of time as it is difficult or impossible to heat irons properly when someone else is poking in the fire and trying to heat other pieces at the same time.
A good fire has three characteristics. It is clean, that is, free from clinkers, cinders, etc. It is deep, with a big, deep center of live burning coke. And it is compact, being well-banked with dampened coal.
Starting the Fire. To start a fire, first clean the fire bowl with the hands, pushing all coal and coke back on the hearth and throwing out all clinkers. Clinkers are heavy and metallic and have sharp hard corners or projections and are easily distinguished from coke. Coke is light in weight and is easily crumbled in the hands. After removing the clinkers, shake the fine cinders and ashes through the grate into the ashpit below the tuyere (that part in the bottom of the hearth through which the blast comes). Then dump the ashpit and try the blower, making sure that a good strong blast comes through. Sometimes ashes work back into the blower pipe and obstruct the blast.
After the fire bowl is cleaned, light a handful of shavings or kindling from the bottom and drop them onto the tuyere. Turn the blower gently and rake fuel, preferably coke left from the previous fire, onto the burning kindling. Once the fire is burning well, rake on more coke, and pack dampened coal on both sides and on the back of the fire. This forms a mound of burning coke at the center. The dampened coal on the outside concentrates the heat in the center. In a little while gases will be driven off this dampened coal, sometimes called green coal, and it will change to coke.
If the fire tends to smoke excessively, stick the poker down through the center, opening up a hole and allowing the air to come through more freely. Most of the smoke will then usually catch fire and burn.
Always use blacksmithing coal in the forge. It is a high-quality soft coal that is practically free from sulphur, phosphorus, and other objectionable impurities. When dampened and packed around the fire, it readily cakes and changes to coke, which burns with a clean, intense flame. Ordinary stove or furnace coal will not work satisfactorily in a forge.
Keeping the Fire in Good Condition. When the coke at the center of the fire burns up, replace it with more coke. This may be done by mashing the fire down in the center with the shovel or rake, or by raking coke in from around the edges of the hearth, or both. Always keep the fire deep. Do not let it become hollowed out and shallow.
Add green coal to the outer parts of the center mound from time to time, as may be required to keep the fire well banked and confined to the center.
Do not continually poke at the fire; simply keep the center well supplied with coke and the outside packed down with dampened coal.
If the fire tends to spread too much, or if it becomes open and loose, throw or sprinkle water on the outer edges and pack it down with the shovel. Use only a moderate blast of air. Excessive air makes for slow heating and scaling of the irons. If a moderate speed of the blower fails to produce enough air, check for leaks in the pipe between the blower and the tuyere, or for a partial stoppage with ashes.
Cleaning the Fire. From time to time — usually every half hour when welding — remove the clinkers and cinders that accumulate over the tuyere. To do this, simply pass the shovel along on the bottom of the hearth to the center of the fire, and then raise it straight up through the fire (see Fig. 432). The clinkers can then be easily seen and removed. Most of them will stay on the shovel.
After the cinders and clinkers are removed, rake coke back into the center and pack it down. Add fresh coal to the back and sides of the fire if needed.
Lining a Forge. Lining a forge hearth with clay, although generally not practiced, will protect it against overheating and rusting and will increase its useful life. A forge hearth may be lined as follows:
- Make a thin wash of clay, preferably fire clay, and spread it over the inside of the hearth and allow it to dry.
- Then mix fine sieved coal ash and clay together, using 1 part of coal ash to 3 parts of clay. Make the mixture about as stiff as putty, and apply it about one inch thick around the tuyere opening and at least 8 in. on the sides.
- Allow it to dry over night.
- Then build a wood fire and bake slowly for at least an hour, turning the blower a little every 10 or 15 min. to keep the fire going.
In using the forge, be careful not to break up the clay lining with the poker or shovel.
Heating Irons in a Forge
To heat irons in a forge fire, place them in the fire in a horizontal position, not pointing down (see Fig. 433). Be sure there is burning coke below the irons, on both sides of them, and on top of them. Keep the fire deep and compact. Irons heat much more rapidly and oxidize or scale off much less when heated in a deep compact fire than in a shallow, burned-out fire. Some scale will form in spite of a good fire, but the scale should be kept to a minimum.
Small thin parts heat much more rapidly than heavier and thicker parts. To prevent burning the thinner parts, push them on through the fire to a cooler place, or otherwise change the position of the irons to make all parts heat uniformly.
For forging mild steel or blacksmith iron, heat it to a good bright-red heat. Do not allow it to get white hot and sparkle. Sparkling indicates burning. Tool steel must not be heated as hot as mild steel. A bright-red or low-orange heat is hot enough for tool steel.
Fitting Tongs; Holding the Work. If tongs cannot be found to fit the work, reshape a pair by heating and hammering the jaws over the piece to be held. Poorly fitting tongs are a source of continual trouble and should not be used.
A considerable amount of work can be done without the use of tongs. An eyebolt, for example, can be made on the end of a rod 20 to 30 in. long and then can be cut off when finished.
Cutting with the Hardy
A blacksmith does much of his cutting of iron and steel on the hardy. Although the hardy does not leave quite as smooth a cut as a hack saw, it is quite satisfactory for most blacksmith work. It cuts faster and easier than a saw and is less expensive, as there are no blades to wear out or break.
To use a hardy, place it in the hardy hole (the square hole) in the anvil, lay the bar or rod on it at the point to be cut, and hammer it down against the sharp edge (see Fig. 434). Hardies may be used for either hot or cold cutting. Some smiths prefer to keep two hardies, one that is thick and stocky and tempered for cutting cold iron, and one that is thin for cutting hot iron. The hardy, like other cutting tools, works better if kept sharp. It may be ground like a cold chisel.
In cutting cold iron, the bar may be nicked deeply on two or more sides and then broken off by bending. In cutting hot iron, it is common practice to cut clear through from one side. Care must be taken, of course, not to let the hammer strike the cutting edge of the hardy, or else both the hammer and the hardy may be damaged. In finishing a cut on a hardy, strike that last two or three blows just beyond the cutting edge and not directly over it.
Cutting Tool Steel. Never attempt to cut tool steel in the hardened state. To cut it on the hardy, cut it hot – not cold – and handle it just like other iron or steel (except, of course, do not heat it above a cherry-red or low-orange heat).