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When to Use MIG Welding vs. TIG Welding



Kevin says TIG welding so precise and so clean, that most of the time, there is no clean up when it's done. You don't have to grind it, smooth it, do anything with it. He does his structural welds with his TIG, but if he has a long run to do - 10 or15 feet to weld - the TIG is much slower than the MIG. He wants his welds to look like TIG welds when he's done, which means he probably has to use his angle grinder to smooth the weld, but he gets his work done. You get short run, highly technical welds from the TIG welder and production runs with the MIG welder.

Wyatt has worked with TIG his entire life. He likes the precision, the ability to weld aluminum, stainless steel, etc. with the same machine and the same gas. When he tries to MIG weld, it sounds so easy to just pull the trigger and weld. He says that with steel that makes sense, but he finds using MIG to weld aluminum is very difficult. Kevin disagrees. He says welding aluminum with a MIG welder with a spool gun is as easy if not easier than welding with steel.

Wyatt gets a lot of questions on his Web site about welding aluminum with a MIG and a spool gun. People buy a welder, say from a hardware store, goes home and welds steel beautifully. Then he puts on a spool gun on the MIG welder and thinks welding aluminum is going to be as easy. He says the spools are typically small and they're usually using 4043 wire and you can't push the wire through the machines quickly enough.

Kevin says they do have push-pull guns that have the rollers in the machines and another set in the gun itself to help pull the wire so you can do about a 15-foot welding run with aluminum. But the push-pull gun is almost the same size as a spool gun - it's big and clunky - and it's very expensive.

Wyatt asks Kevin to compare the TIG and MIG torches. Kevin shows the TIG torch and the pedal, because the torch doesn't have a trigger on it like some TIG welding torches do. Just like a gas pedal in a car, the harder you push on the pedal, the more electricity goes to the torch, the hotter the arc is, the faster you weld. As for the torch itself, there are lots of parts and pieces, including a torch body and a gas lens. Kevin shows the mesh inside the gas lens and explains there are several different layers of this mesh. The graphics show the gas with and without the lens, illustrating how straight and smooth the gas comes out when using a gas lens, greatly increasing the coverage. Kevin says a gas lens is a great addition to any TIG torch.

Then he shows the tungsten. Swain says he carries tungstens of many sizes at TIGDepot.net, from 20/1000s diameter up to 5/16 and even up to 1/4 inch diameter for heavy duty welding. Kevin shows one Wyatt uses for micro welding. Wyatt says you can use 40/1000s, grind a fine point on it, and light an arc at two or three amps. Kevin says this one is about the diameter of a safety pin and just as sharp as one. Kevin then shows the collet body, then the collet, then the back cap. Then he shows how the tungsten goes inside, and he tightens it down by tightening the back cap.

Then he adds the TIG cup to help the flow of the argon gas as it comes out. The cups come in different diameters. Wyatt explains sometimes the orifice opening size is critical, which is helpful when you are welding with lower amps the diameter is much smaller and you turn your gas down accordingly. Kevin adds that a smaller cup also lets you get into tighter spaces, while the bigger diameter TIG cup gives you wider coverage. Kevin also adds that you can have a smaller end cap (or backcap) - again, helpful for getting into smaller spaces - or have the full-size end cap that lets you use the entire 7" tungsten at one time.

Then Kevin shows the MIG gun, or MIG torch. It has a trigger and it has a nozzle. It also has a tip, or electrode, although they are usually called tips. You have different sized tips for different sized wires that feed through them. Then he shows the brass connector that holds the liner in the cable that the wire feeds through to make it easier on the feed roller. There are also holes to allow the inert gas to come through the nozzle to shield your work. It's pretty simple.

Swain asks Kevin about the shielding gas. Kevin explains you normally use 75% argon and 25% CO2, which is commonly called a MIG mix or MIG gas. Occasionally you'll use what's called a tri-mix, which is argon and carbon monoxide with a little helium in it for when you are welding stainless steel so you can boost the heat a little for the harder metal.

Then there's filler rod. With TIG, you have a three-handed process - or two hands and a foot. You have to hold the torch, feed the filler rod, and your foot runs the electricity to make it hotter or colder so you can feed it all in. So when you want to tack, you need another hand to hold it in place. Kevin says Swain is probably a lot better tacking with the TIG welder. Kevin likes to have both machines set up, so when he tack welds, he reaches for the MIG, because you only need one hand to hold the gun and can hold the work with the other hand. Then he'll come back and do his finish work with the TIG, with its nice, beautiful clean welds. With MIG you get a little splatter. It's not nearly as bad as using a stick (arc) welder as there's no slag to clean up, but he still finds he needs to clean up his work after MIG welding to get a smooth surface.

They have a Linclon SP-135 Plus 110-volt MIG welder with solid-core wire in it and gas, as well as some 16 gauge and some 1/2" plate to show what it can do. The SP-135 Plus is the biggest transformer machine that runs on 110. Inside, it has a spool of wire, a feed roller that sends the wire out the gun. There's a positive and negative connection that is switched to accommodate solid-core wire or flux core wire (flux core is used without gas). The connections are also changed when you use a spool gun. There's a handy chart that shows the various connections, metal thicknesses, wire, gas, processes, etc. that gives you someplace to start from. On the front of the machine is the on-off switch, an arc-volts dial from A-J to control voltage, and a wire speed dial. Now he's ready to make some sparks!

With a little pull of the trigger, he is able to MIG weld. There are some tricks you learn, including learning to spot the bubble. The welder easily welds the 16 gauge. Now he turns up the voltage all the way, the turns up the wire speed, and welds some 1/2" plate. It's that easy. For the 1/2", Kevin would usually use a 200- or 250-amp machine for welding something that thick and cold, although he has preheated thick metal with the oxygen-acetylene torch and then come back with a lower powered machine to weld it.

Wyatt says it welded the 16 gauge beautifully, but clearly they took it to an extreme to weld the 1/2" metal. This welder is not recommended to weld that thick of metal - Kevin says it probably can handle 3/8" at the most - but it did work. Wyatt says anytime he uses MIG he rarely exceeds 1/8".

Kevin says if you can afford a little more power, get it. If this is what you can afford and you are playing in your garage and are building stuff for your house, this is a great machine that can handle 75% of what you need. But once you get used to it, you might grow out of it, and you'll want to move up. It's still a handy machine, though, even for Kevin when he has to go outside, go on location, places he doesn't have 220. He can drop the wire size and up the amperage to make it hotter and still work in the field.

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