Smith welding is the process of joining metals by laying the pieces together and hammering at the place of contact until they become one piece. Most metals must be heated nearly to the temperature at which they begin to flow, before they can be welded. For iron and steel this is at the white heat; so let us first consider the action of the fire and the equipment required before taking up the study of the process in detail.
The combustion of fuel, either coal, coke, oil, or charcoal, causes the oxygen of the air to combine with the carbon of the fuel, and this chemical combination is what produces the heat. The amount of heat produced depends upon the amount of carbon and oxygen combined during combustion; whereas, the temperature attained depends entirely upon the rapidity with which the combination takes place. This is one of the most important facts to be learned in connection with welding, because the principle involved applies to all of the other systems of welding as well as to smith welding.
Ordinarily, combustion would not be rapid enough to generate the amount of heat required for welding; so a draft is created through the fire in order to supply enough oxygen to the fuel and increase the rate of combustion. Too much air will chill the fire or blow it out, and an excess of oxygen will cause some of it to combine with the iron and form a scale of oxide of iron. This is called an "oxidizing fire"; whereas, if the oxygen is all consumed in the fire and there is an excess of carbon, it is then called a "reducing fire".
Coal, coke, charcoal, oil, and gas are all used as fuels Tor forges, but charcoal is the best because it is almost free from impurities. Coal and coke are good unless they contain sulphur and phosphorus. Sulphur makes iron "hot-short", or brittle when hot, and phosphorus makes it "cold-short", or brittle when cold.
Fig. 1. Brlok Blacksmithing Forge.
Forges are of various kinds, usually of brick or iron, Figs. 1 and 2, and consist primarily of a bowl with an air inlet or "tuyere" in the center of the bottom, a hood overhead to carry smoke and fumes to the chimney, a blower or bellows to supply air, an ash pit, and a trough or other vessel for water. Usually a blast of air at a pressure of from 4 to 6 ounces per square inch should be maintained. A type of portable forge is shown in Fig. 3.
An anvil is required to provide a sur-face upon which to lay the pieces, when hammering to make the weld. It may be of cast steel or of wrought iron with a steel face, and usually weighs from 150 to 200 pounds. The anvil should be placed on a block of hard wood, Fig. 4, and securely fastened to it, and the height should be such that a man's knuckles will just reach to the top of it when he stands alongside.
Hammers and sledges of various sizes and styles are required. Hand hammers, Figs. 5, 6, 7, and 8 weigh from 1 to 2½ pounds and have handles from 14 to 16 inches long. Hand sledges, Fig. 9, weigh from 5 to 8 pounds and have handles from 24 to 30 inches in length. They are handled by a helper. Swing sledges, Fig. 10, weigh from 8 to 20 pounds and have 36-inch handles, They are used for heavy work only and the helper strikes a blow with a free full-arm swing.
Fig. 2. Modern Motor-Driven Forgo.
Courtesy of Canedy-otta Company.
Ball-peen, or chipping, hammers, Fig. 7, have a round top or ball-shaped peen on the head. The striking face is flat, but the peen head is used for riveting or for stretching metal by hammering. Cross-peen hammers, Fig. 8, have a long ridge running across the top of the head and are used when stretching metal lengthwise and for riveting. Straight-peen hammers, Fig. 5, have a ridge running lengthwise of the head and are used when the metal is to be spread sidewise. Hammers should be selected to suit the work to be done and the strength of the user, and they should be of the best quality.
Fig. 4. Anvil Fastened to Block.
In addition to the foregoing hammers for general use, there are various kinds for special purposes. These include "set" hammers of various shapes, for forming the iron. Square set hammers, Fig.
Fig. 3. Portable Hand Forge Courresy of Canedy-Ous Company.
Fig. 5. Straight- Peen.
Fig. 6. Long- peen.
Fig. 7. Ball- poen.
Fig. 8. Cross-Peen Hammer.
11, are for producing flat surfaces; flatters, Fig.
12, are for similar use but cover a wider area; fullers, Fig. 13, are for spreading out the iron, hollowing out work, and forming shoulders; swages, Fig. 14, are for rounding pieces of iron and are of numerous sizes; punches, Figs. 15 and 16, are for making holes and are made square and round; and cutters, Figs. 17 and 18, are hammers with chisellike edges on the top of the head for cutting bars, etc.
Anvil tools with stems to fit the square "hardie" hole in the anvil are made in shapes to match the set hammers previously described. They include fullers, swages, hardies, heading tools, etc., Figs. 19 and 20.
Fig. 9. Hand Sledge.
Fig. 10. Swing sledge.
Fig. 11. Square Set Hammer.
Fig. 12. Flatter.