Arc welders are designed to weld metal together using a consumable welding rod. When an electrode clamped into the holder is brought close to the grounded parent metal, a high amperage arc of electricity crosses the gap between the surfaces. The resultant arc produces a temperature high enough to melt both the parent metal and the consumable electrode. The two molten metals then puddle together, and when cooled, form a permanent homogeneous joint between the two surfaces. In addition, with special cutting rods and the right technique, you can also use an arc welder to cut through ferrous metal.
Things You'll Need
Arc welding machine
Welding face shield
Special cutting rods
Prepare your welding machine by inserting both the earth lead and the welding rod handle lead into their respective color-coded sockets on the side of the machine. Adjust the welding amperage to its highest setting.
Mark a clear cut line on the steel or cast iron with a piece of engineer's chalk.
Clamp the bare end of a special cutting rod into the forward-facing groove in the welding handle so that the rod sticks straight out in front of the handle. Don a pair of welding gloves and slip a welding face shield over your head without lowering the visor.
Line up the cutting rod parallel with the cut line. Position the tip of the rod 1 inch away from the cut line and lower the welding visor.
Lower the tip of the cutting rod onto the metal to establish a high-pressure arc. Maintain full contact between the tip of the rod and the parent metal, and push the rod along the cut line with a gentle back and forth motion. The high-pressure arc from the cutting rod will blast molten metal out of the cut line. This action will cut right through 3/8-inch thick or less metal plate, or gouge out a deep groove in a piece of thicker metal.
Repeat by deepening the groove the same way until the thick piece of steel or cast iron is severed through the cut line.
Gauging out a series of deep grooves to form a "V" in preparation to welding cast iron not only prepares a good surface for your first bead by burning off excess graphite, but it also pre-heats the parent metal. This extra heat prevents the filler metal from shrinking too quickly as it cools down, causing a stress crack next to the weld. In addition, hammering the bead flat with the round end of a ball-peen hammer as the weld cools will stretch the filler metal, thereby relieving some of the stresses caused by shrinkage.
Always wear heavy leather gloves when welding. Never look at the arc or bounced ultraviolet arc reflection without wearing a dark-shaded arc welding visor.