Butt welds: If the butt weld is carefully made it is perhaps the safest weld of all. This method is used mostly in welding round iron bars, 11⁄2 ins. in diameter up to 21⁄2 ins. They are made as follows: the ends of two bars are heated to a welding heat. Then they are brought out of the fire, put in a swage, end to end, and struck on the ends with a sledge hammer. While driving upon the ends the iron upsets when the contact takes place and at the same time the smith is driving the weld down. Two processes are acting here, one lengthwise and one downward. This makes the best weld, from the fact that the two ends that come together have a welding heat on the whole surface of each, a condition hard to get in any other kind of weld.
Flat Scarf
Lap weld: Two flat pieces are laid face to face, as shown in picture, and are welded. One must be careful that the two pieces have the same temperature, otherwise the colder piece would cut into the hotter and make a defect.
Split scarf, cleft weld
Cleft weld: If the weld is required to stand much strain, such as in parts of a locomotive frame, pieces are generally joined by the cleft weld. One piece is upset and split with a chisel. The two sides are spread apart. The other piece is scarfed on both edges to fit into this opening. If the pieces are very large much of the welding can be done while in the fire. The two pieces are placed together, in the proper position, in the fire. When the heat is hot enough to weld they are driven endwise. This drives the point of the one piece into the crotch of the other. Take them out of the fire and place upon an anvil or under a hammer. Small pieces are welded in the same way, except they may be driven with a hand hammer on the end just before driving upon the surface. The piece is reduced to the proper size and finished.
Jump weld: When one piece of metal is to be welded at right angles to another piece, a jump weld is made. Many are made by using a bob punch, making a hollow depression in a flat piece, and a rounded or button head shape on the end of the upright. Heat the end of the upright and also the flat piece around the bob punch hole to a welding heat. Take them out of the fire and drive the button head down into the hole made by the bob punch.
