Tig Welding Basics

Last month we looked at the MIG process, which is definitely the most popular type of welding used for classic trucks. This month we'll explore TIG welding, which many people consider the premiere welding process.

Since MIG welders offer a good-quality weld with a moderately priced machine, coupled with high strength and high speed, why would you consider anything else? It really comes down to control, versatility, and the hardness of the weld bead.

TIG welding produces temperatures up to 35,000 degrees Fahrenheit, yet this concentrated heat can be precisely controlled and directed. When filler metal is required, it can be added manually by feeding welding rod into the puddle, similar to oxyacetylene welding. In fact, oxyacetylene welders usually pick up TIG welding fairly easily.

TIG welding involves a handheld torch that holds a slender electrode through which the welding current passes. The electrode is surrounded by a ceramic cup that directs the flow of an inert shielding gas (usually argon), which keeps atmospheric oxygen away from the weld zone. Most machines have a foot- or hand-operated control that changes the welding current on the fly. These features offer unrivaled control over all aspects of the welding process. A skilled operator can make a weld that has good penetration with a small, crisply defined, low-profile weld bead that is quite ductile, or workable. The workability of the weld is an enormous advantage for high-end bodywork, since the best way to repair the distortion caused by welding is to hammer on-dolly on the weld bead. MIG welds, while quite strong, are more brittle than TIG welds, and may crack if they are hammered too much.

TIG welding can bond just about any metal. Not only is it great for steel and aluminum, but it's also great for stainless, titanium, copper, bronze, and magnesium, to name just a few.

TIG welding has been around since the 1940s, and although it was considered esoteric at first, now that many people are aware of its advantages, the machines have become quite popular and affordable. Most of the better street rod shops (and many serious home builders) utilize TIG welding for both body and chassis work. Once you've become accustomed to the incredible control it offers and the beautiful look of a well-formed TIG weld bead, most people get hooked!

The type of TIG machine you should purchase depends on the type and thickness of metal you'll be welding. A TIG welder with a 180- or 200-amperage output and AC/DC output capabilities will handle most automotive applications. (You need both AC and DC output if you want to weld on steel and aluminum.) For bodywork, it's a real advantage to have a machine that will go down to very low settings-starting a weld around 5 or 10 amps is often beneficial. Some older machines only go down to 25 amps, and it's a bit tricky to do delicate welding on very thin metal with that much amperage.