The Stovebolt Site Forums The Shop Area The Tool Chest MIG v. TIG for sheet metal

I'm going to fill some holes and do some other cleanup/patch work on the sheet metal of my '57. I have a Promig 140, but I've been led to believe that MIG welders generate too much heat, and for sheet metal repair TIG is the only way to go.

Does anybody have an opinon? (About MIG v. TIG welders, that is.)

Only a opinion but I feel more heat is generated with the tig. It's more like a electric torch.

Tig will produce a smaller more precise weld that will require much less grinding than if done with a mig welder. Tig is not forgiving of poor fit up at all, whereas you can fill bigger gaps with a mig. Everybody is always worrying about which produces less heat. This really is not that big of an issue if you skip around with a series of SMALL tack welds. Grinding down larger mig welds with a grinder also produces heat and you can work harden the material if not careful. Another advantage to tig is you can immediately work the panel with a hammer and dolly while it is still hot, similar to gas welding (oxy/acy.). Master coach builders still prefer oxy/acy welding to any other, and when you're good at it you won't use any body filler.

Tig welding will do a superior job, but your mig welder would really be fine for this...use what you got! You can also get soft mig wire that grinds more easily for doing body work.

Desert_buick,

I think most people do bodywork on a hobby basis with MIG. It's fast, easy and the equipment is available anywhere and everywhere.

TIG is much more specialized, and the equipment is much more expensive. While building half doors for my son's Toyota recently, I was working with new 18 gauge steel and wanted to see the differences between these two processes myself.

I used TIG to weld two small pieces together...it was very clean, controllable and warp free, even with filler material.

We built the doors with MIG, and although no longs welds were involved, we successfully welded the 18 gauge to the even lighter Toyota sheetmetal with no burnthrough or warpage.

This was done with shielding gas and .023 wire. We have all seen the TV shows where almost everything is TIG'd. They are fun to use. The clarity of the weld puddle and control of the weld is incredible, but for me, the MIG process was more than adequate for the job on the thin sheetmetal.

Technically, I think the TIG produces much higher temperatures than MIG...but they are much more focused and they are controllable during welding. As they say, my two cents.

Stuart

Thanks all for the good info. The silver lining to all the bad sheet metal is that I have a lot of material to practice on. Of course, not spending $1200 for an entry level tig welder makes me a pretty happy camper.

you should be able to buy a gas kit to enable your welder to use 75/25 argon/co2 mix, your weld will be much cleaner w/much less grinding. Brian

if you are a GOOD welder, get a tig. If you are a novice, use the mig

Fireballv8,

Would you mind if I modified your statement...If you're a GOOD welder, stick weld it, if you're a SMART welder, MIG weld it....If you're a RICH welder, use TIG.

Stuart

I have been using "Harris 20 gauge" for doing some panel repair and filling holes in the firewall on my 48 5 window. This is .030 flux wire for a mig welder to be used with shielding gas. Makes a nice flat soft weld, easy to hammer immediately or when grinding.

If you are a good welder, you aren't asking which is better MIG or TIG, for welding sheet metal. But we aren't all good welders. TIG is superior for welding aluminum, stainless steel, magnesium, titanium and chrome-moly.

An entry level MIG machine running .030 or .023, solid or flux core wire and straight CO2 or Argon/CO2 is more than adequate for welding sheet metal. The experience is also priceless. Good luck with your project and Happy Holidays.

Tony

GMAW (MIG/flux core)is the most common process for sheet metal repair and fabrication used today. It's low cost, speed of use and relatively low learning curve is the reason why. Specialty wires are available for use with the process. ESAB EZ grind is one and most any dash 2 wire (ER70S-2) wire in a small diameter (.023/.030) used with C25 (75% argon/25% CO2) are the better choices. Straight CO2 gas is reactive and aids penetration on thicker materials and will increase the likelyhood of opening up holes in the less skilled welder. Dash 6 (ER70S-6) wire can be used where grinding is not required. These and other wires are quite hard and grinding can generate enough heat to warp panels and the surrounding sheet metal will wear away faster. Just remember that dash 2 wires are considered non-structural and you will need to change it out before working on frames and such. FCAW with or without gas (depending on wire requirements) can also be used with good success. Keep your stickout short and use a low push angle and spot and/or stitch weld to control panel heat. Do not cool welds with water or shop air as this will also harden welds and warp panels. Heat control putty is also available. The new GMAW machines with soft start and pulsing are great machines for sheet metal work. GTAW (TIG) is also great for sheet metal through thick section. Much higher learning curve and skill level. Slow production speed. Originally developed as a replacement for oxyfuel. Has the advantage of being able to weld most metals and offers superior control of heat and awesome flexability. Must higher cost for equipment and labor. Miller and Lincoln offer lots of process info on thier sites. http://www.millerwelds.com/education/library.html
http://www.lincolnelectric.com/knowledge/

Good info Jim!!!