The Tungsten Inert Gas (TIG) welder generates heat from an electric arc between the electrode at the tip of the torch, the filler rod, and the metal part that's being welded.
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The electrode is made from tungsten and tungsten is the same material in light bulbs, but instead of creating light, it's creating heat -- enough heat to melt metal. That is basically what welding is -- heating metal.
There is a grounding cable that clips on to the work piece itself, or the welding table. It acts just like the lighting rod on the roof of a barn. It takes the excess electricity, conducts it down the cable to the frame of the welder and neutralizes it.
In order to create a strong weld, you don't want any contaminates to get into the metal while it's in liquid form because that will weaken the weld and cause cracking over time. Inert gases are gases that don't combine easily with other elements -- like metal. The inert, argon gas in the tank is pumped through the welder to the tip of the torch where a small amount is released. This creates a gas shield around the weld keeping out any contaminates until the metal hardens.
TIG welders range in price from $1,000 to $3,500, but you can rent one from an industrial rental supply company.
Welding involves an electric current that instantly generates 1,600 degrees of heat and a flash of light that's so bright it could blind you. A welding mask protects your eyes from the flash of light and it covers your entire face and part of your neck as well. You also need to protect your hands and arms by wearing leather welding gloves and a long sleeve leather welding jacket. This is important because the bright light can actually burn you just like sunburn. The sparks are five times hotter than the chop saw.
Metal warps from the extreme heat when welding. This can throw things out of whack, so in order to keep the warpage to a minimum, and to keep all of the parts perfectly aligned, you can construct a jig using scrap angle iron. Pieces of angle iron can be cut to match the drawing and then simply tack-welded onto the table. A tack weld is a temporary weld used to hold a piece in position until a permanent weld can be made.