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When any of the foregoing welds are to be made, or similar cases arise, a 3/32-inch rod is used with a heat somewhat stronger than should be used on sheet metal only. In fact, the heat can be considerably greater if the tip of the welding rod is held directly over the heavy material, and the weld laid along the edge of the sheet metal. This eliminates burning the sheet metal, and a strong, neat weld will be the result.
When the machine is not in use, always place the dial switch at the "Off" position, as the transformer is then electrically disconnected from the 220-volt line.
Spring steel welding
A very satisfactory butt weld of good strength may be made, as in the case of a bumper, by welding both sides of the break, but if exceptionally great strength is desired, it is advisable, after the butt weld is completed, to weld a short piece of spring steel over one side of the bar, and to weld the edges only. Never, in any case, weld the ends of the piece applied, as to do so will defeat the purpose of putting on the extra bar, because the temper in the large pieces will have been destroyed.
Note—In the case of fairly thin pieces of the foregoing material, they may be butted tight to each other before welding, but when heavy material is encountered, the edges should be bevelled or placed not closer than 1/8 of an inch apart.
Because of the characteristic of cast-iron to crack after welding due to expansion under heat that has been built up and the consequent contraction when cooling, it is necessary to weld not more than 1/2 inch at a time.
Proper preparation of the joint is essential. The joint should either be ground or beveled out with a chisel. The wider the bevel, the greater the fusion. If the item to be welded is preheated, longer welds can be made. ( To heat an engine block, drain water and run engine until block is hot.)
The welding technique is the same as for steel, but in addition to being limited to 1/2 inch at a time, it is also advisable if an exceptionally long crack is to be welded to make a 1/4-inch tack weld, spaced about 2 or 3 inches apart.
It is good practice to lightly peen the bead during cooling, as this will tend to relieve locked up stresses.
Important: Always use Allen cast-iron rod and the least heat possible to do the job, so as not to affect the quality of the casting being welded.
Malleable iron welding
The same technique is used in malleable iron welding as in cast-iron, either of which metals can be welded separately, or joined together, or either can be welded to steel. Use Allen cast-iron rod.
Welding cast aluminium
Cast aluminium is very satisfactorily welded, as in the case of aluminium cylinder heads, by putting into the electrode holder a short piece of 3/8-inch welding carbon and using a medium heat. The carbon is used to maintain the arc, and a 1/8-inch or 5/32-inch coated aluminium welding rod is fed by the operator's other hand.
Note.—It is important to remove all scale from an aluminium weld before going over it a second time, or starting again after breaking the arc.
Brazing is done with a carbon in the electrode holder, the same as with aluminium, and a coated brass rod is fed into the arc. To use the carbon electrode, sharpen it to a tapered point, approximately 1/16-inch in diameter at the tip, tapering back a distance of at least 3/4-inch. Grip the electrode back 2 1/2-inches to 3-inches from the tapered point.
When it is desired to build up an angle formed by two pieces of metal to be welded, it is best to build several layers of welding, one on top of the previous one, until the desired depth is secured.
The cutting of metals is best accomplished with a medium or large-sized steel welding rod, using a medium or high heat. The method used consists of moving the rod back and forth over the part to be cut, and with this movement slowly progressing ahead. In the case of vertical cutting, always start at the bottom to allow the molten metal to fall away instead of piling up on the metal being cut. Using a nibbler is a way of cutting mtal.
Do not look at a welding arc without the protection of a helmet or hand shield. In case of eyeburn, there will be no permanent injury, although the pain may be considerable for several hours.
Allen welding rod
Always use A.C. welding rod. D.C. rod is very different in action, and causes difficulty in striking and maintaining an arc, and the deposits are in small beads or drops, which cause a rough finish weld. Furthermore, the dropping action of D.C. rod produces minute temporary shorts in the welding circuit, and, in the case of a long continuous operation, raises the transformer temperature above normal.
Good A.C. rod enables the operator to strike and maintain an arc easily, and give a strong non-brittle weld. An important feature of Allen's rod is that the welded joint has a minimum tensile strength of 50,000 pounds to the square inch, and the welds, even in the case of cast iron, are tough and ductile, which may be machined, ground, or filed, with the same ease as the parent metal. This is because the coating on the rod shields the arc from the surrounding atmosphere, preventing oxidation, and finally deposits itself over the finish weld, allowing it to cool slowly.