Plug Welds - Mig or Tig?

[strokedelky]

I am a welder by trade but don't do too much sheetmetal. I'm in the process of replacing the roof skin on my El Camino (had a sunroof) and I was wondering which would be better. Mig or tig for the plug welds? I know most do it with a mig but was thinking tig may be a little less work afterwards (no welds to grind down). What do all the experts here think on this?

Thanks, Darren

[72chevellephil]

use mig,the tig will warp the hell out of any large panel you weld up.tig is the worst for plug welds.phil

[strokedelky]

Thanks, 72. I was kinda thinking like that just thought it might save a little grinding afterwards. Oh well, no big deal.

[Taylor1969]

Once you get in a groove grinding isn't all that bad.

If you prep well and setup the welder plug welds with a mig shouldn't be that bad. Just make sure to use a punch to make a bunch of holes and start welding.

https://static1.pt-content.com/images/noimg.gif

[ahowudoin]

I never would of thought that tig was that hot. I thought it would have been better, Just take longer. Guess you learn something new everyday.

[Duesey2]

I have a tig and mig and have experimented with an infrared gun after each when spot welding. They both emitted the same amount of heat after several experiments. The tig is easier to dress out though. Mig is much faster for me and I don't have to mess with a foot pedal. I use the tig on delicate areas.

[chdnny]

I have a tig and mig and have experimented with an infrared gun after each when spot welding. They both emitted the same amount of heat after several experiments. The tig is easier to dress out though. Mig is much faster for me and I don't have to mess with a foot pedal. I use the tig on delicate areas.

even if they were the same temp wouldnt the tig have a bigger heat afftected area?

[MonzaRacer]

Tig hotter than mig, not if you have control of the weld.
Heck I would rather see a sheet metal part tiged over mig anyday.
Mig is simply faster in the filing part.
As for heat if you think its gonna be hot NAPA has a spray gel heat blocker that isolates the weld area very well I got one bottle off of the MATCO truck but it has since been discontinued. But NAPA selsls it in the Balkamp book.
If you can weld 2 razor baldes together with a tig how can it make a "hotter" weld or cause warping?
Never seen it and if your a welder you know how to control your heat for the weld process.
Good luck.

[hotrdblder]

tig is not hotter, when tig welding you have the heat on the material for longer periods cauing the heat to get out further then stich welding with mig, i like to do 3-4 tacks to form a stich, but 99% of the time i am doing plug welds/glueing as i replace the entire panel, there is a reason oems used pinch welds etc

[strokedelky]

Well, just to let everyone know I got it all finished up on the weekend. Most of the plug welds were in the front and rear window openings and along the drip rail. I played around a little bit and found for most MIG was preferred but there was some welding needed on the roof skin itself above the windshield and TIG was my friend. Nice small profile and a narrow heat effected zone with 1/2"-3/4" long stitch welds. A 36 grit disc on the angle die grinder made short work of the welds afterwards. Thanks for any and all replies.

Darren

[derekf]

Darren, do you have in-progress pics of the roof replacement? I'm in the same boat with my Camino and its sunroof.

[Taylor1969]

Darren, do you have in-progress pics of the roof replacement? I'm in the same boat with my Camino and its sunroof.

most of my pics can be found here...

http://s205.photobucket.com/albums/bb172/taylor1969/

[cheapthrillz]

Im not sure who makes it, but you can get a thumb amp control that is much easier to work with than the foot controls (my opinion).

[rich-allen]

When welding with tig, the surrounding material is almost three times hotter than any other type of welding.
Weld deposit is instantaneous from a mig. The surrounding material is affected as the heat dissipates.

There are instances where tig would be a better option but this is not one of them.

Finally a thread I can relate to. :slap:

[hotrdblder]

When welding with tig, the surrounding material is almost three times hotter than any other type of welding.
Weld deposit is instantaneous from a mig. The surrounding material is affected as the heat dissipates.

There are instances where tig would be a better option but this is not one of them.

Finally a thread I can relate to. :slap:
exactely

[gt1guy]

When welding with tig, the surrounding material is almost three times hotter than any other type of welding.

I'd like to know how you came to this conclusion. A welding arc is roughly 7500 degrees. That goes for MIG, TIG (AC and DC), stick, what have you. If TIG welding puts three times the heat into the material, wouldn't the HAZ be roughly three times the size? That would make TIG a terrible choice for just about any precision welding, and that's just not the case. DC TIG, when set up correctly, will have LESS heat input into the material than other types of welding, mainly because the arc is so finely focused into such a small area.

Would I TIG plug welds on body panels? No, it would be a waist of time, and take too long. MIG works just fine for that, when set up correctly. Can it be done? Sure it can. I would make the holes to plug weld much smaller than if I was going to MIG them. The reason for the smaller holes is two fold. 1. you can get away with it with the finely focused arc of the TIG, And 2, it will take longer to do the weld with TIG and therefore you will end up with more heat input, which is not what we want on body parts. I know this just sounded like I'm agreeing with what you said. But I'm not. The key point here is time on location.

I'll shut up now,

Kevin

[strokedelky]

cheapthrillz, I have seen a few different thumb controls but don't have one. So it is foot control for me for now. And it is ackward in some postions - like when you have to stand.

derek, I have some pics before, during, after on my computer but I don't have them hosted anywhere - still thinking about getting around to that. So all I can really do is e-mail them and type some explanations, but it is quite like Taylor1969 pictures. He has some good shots in his link. Also I didn't start with a new skin, I had cut a roof off of a wreck a while back - just took more prep work.

Darren

[gt1guy]

Look on Miller or Lincoln's sites for thumb controls. If you have a el- cheapo brand machine, you could probably make one work provided the machine has a remote receptacle. It is just a reostat(sp?).

Kevin

edit: spelling

[strokedelky]

Kevin, I have seen the controls but haven't bothered - just being cheap. However, no el-cheapo brand machine, not the biggest machine but a Miller Dynasty 200DX does well for me at home. One of these days I'll get a thumb control but most projects I do at home I can sit and relax at the bench so a foot pedal does fine.:)

Thanks, Darren

[gt1guy]

The Dynasty line are great machines. We use the 350's at work for wet stick and hyperbaric (habitat) TIG welding. Love em.

Kevin

[parsonsj]

Thumb controls do help in awkward positions, but they have one drawback (at least for me): rolling the control affects the tungsten location and arc. Perhaps my technique needs work, but I've never had much luck in small amperage changes while the arc is struck.

jp