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    The process of using an arc welder, which involves feeding powerful electrical currents through the air, metal, and various other resistant substances in order to create a continuous circuit out of the welding machine, through the workpiece, and back again, makes use of some highly concentrated forces. The intense exchange of electricity tends to build up a powerful magnetic field around the arc as well, whose magnetic lines cling to the wire and surround the arc itself.

As noted in the previous article, the longe r a welding cable is, the thicker it needs to be in order to accommodate the flow of electricity without providing enough resistance to cause dangerous heat to build up. Similarly, the higher the amperage that you are using to weld, the stouter the cable must be, again to avoid overheating. Higher amperages impose limits on the maximum length of a welding cable as well. Even the longest 500 or 600 ampere cables are very short indeed compared to a long 100 ampere cable.

Open root welds are a very common type of weld when joining two plates together edge to edge, and are used in a large number of pipe welding operations as well. Open root welds are made when a narrow gap is left between the edges of the pieces which are being joined, a gap which is then filled by the first weld bead. Multiple weld beads are then applied in the root to complete the weld. The number of weld beads needed depends on the thickness of the metal, which is usually beveled to produce a channel above the root gap.

The welding cable used to connect the main body of a welding machine and the welding gun that is held by the user bears more of a resemblance to a pipe or hose than might at first be imagined. Just as a hose needs to be large enough to accommodate the volume of water that is being pushed through it or it will burst, so a welding cable needs to be physically large enough to handle the volume of electricity that is flowing through it, or it will overheat and possibly malfunction.

Laying down a good root pass is the backbone on which the rest of your open root welding efforts will hang, so it is best to be highly attentive to this bead and do everything you can to make it perfect and pristine. This initial pass is the foundation for the rest which follow to fill in the channel that has been cut in the two pieces of metal, and a number of special methods and even specialized pieces of equipment have been developed to help welders get it right the first time.

Using backing strips for the root pass

Vital as it is to the success of the whole join, the root pass is only the first part of what is usually a multistage welding process. The root weld needs to be cleaned and completed as much as possible, since it is going to be buried beneath subsequent weld beads and thus rendered totally inaccessible without severing the entire weld. Thus, it is best to ensure it is as clean and well made as possible before proceeding.

Finishing the root pass

    There are four positions in which you might find yourself welding – flat, horizontal, vertical, and overhead. Flat welds are those which you make with the weld bead being laid down along a horizontal surface, even if one of the pieces you are welding is sticking up vertically, at a 90° angle to the one lying flat. Horizontal welds are those made from side to side on a vertical surface.

    Plug welds and slot welds are specialized types of welds that are made to join two pieces of overlapping metal together, without the need to lay down a fillet weld along the edge of the metal. These welds may be used for a variety of reasons. One is aesthetic – a properly laid slot or plug weld may be almost invisible once you finish the metal piece with paint or other coatings, whereas a weld bead is always visible to some extent.

    Welding joints in metal is a mix of straightforward processes and complex requirements, and although it is beyond the scope of this article to sum up all of those complexities, there are certain matters about welding joints that you should be familiar with. There are also several types of highly unusual joints that are seldom used, but which should be mentioned here.

Edge joint welding

    The human mind is always questing after new ways to do common tasks, and the different welding methods are no exception to this drive to explore and innovate. All of the major joint types have a number of different variations, which you might want to use depending on what kind of welding job you are working on. Tee joints and lap joints have far less variations apiece than butt joints, but they are not lacking in variety, either.