Learn me MIG for Bodywork

I've thusfar been using my TIG for everything, but I've found a challenge I can't meet with the TIG. I'm fixing a tear in a unibody on the underside of a car. Between the location, material thickness, nasty environment, and my skills, I just don't see success coming out of this problem being tackled with the TIG. So I'm MIG shopping. I'm about 3 hours from picking up a Hobart Handler 187 from Tractor Supply over my lunch break.

The specs say it will weld down to 24 Gauge. The chart says to use the low tap and 30 amps with .023 wire, so that will be my starting point. I've got a bottle of 75/25 Argon/CO2 and a bottle of 100% argon. I assume I want the mix gas for the MIG.

Any other tips? I haven't MIG'ed in years, and this is a less than perfect place to learn a new welder, but it is what it is.

Yep, you'll want the MIX.

Welding sheetmetal is tough--at least for me. Very hard to get that fine line between proper heat so that the weld will puddle a little bit versus blowing a hole through the metal.

I'd start with floor pans and other 'horizontal' surfaces before you try external stuff...floor pans are a lot less noticeable than quarter panels.

all other tips (clean, well-lit, good visor, etc) also apply.

You definitely want the 75/25 for MIG work. I've used gasses from 95/5 all the way to 100% CO2 over the years with different MIG welders (and for different purposes), and 75/25 is the "one" for general purpose work.

I've been using a Snap-On 185 amp welder on cars for, oh, 25 years now. It's enough current to weld anything up to 3/16" thickness in one pass, and 3/8" thickness with two or three passes. Nothing like the 600 amp monster I used to run at work, but for car stuff you just don't need that.

Using .023 wire you should be able to weld 24 gauge sheet metal, no problem. Heck, I often leave the .030 wire in the machine and play with the feed and amperage to get the job done. Backing the weld up with a copper or brass bar is helpful, but of course you often can't do that.

I guess the only other tip I can think of is to carry your good welding habits over from TIG - good ground, clean welding gun (watch for spatter build-up in the cup), clean area around the weld, the usual stuff.

I've heard that pure Argon isn't used because of poorer penetration. Can this be used to help avoid blow-thru on the thin stuff though?

I'm not in any way an expert, so take this with a grain of salt, but if you can't do it with TIG, I doubt MIG will be any easier. My (limited) experience is that MIG is not any more tolerant of dirt and rust, and you have less fine control over the power level since you don't have a foot controller...

-Chris R.

i havent used it much except in a couple NASTY areas i just couldnt get fully clean, but flux core wire does tolerate an unclean environment a bit better than gas mig and surely tig. they end up not super pretty and i dont know how low it'll go but if it isnt really visable it could help you maybe?

If the sheet metal is galvanized or zinc coated (which it probably is) I use Muriatic acid to remove it. Scrape undercoating, grease etc. first, remove paint w/ sandpaper. Brush on acid, you'll see the reaction, DO NOT breathe the fumes!! Wear your PPE. Acid removes the coating and digs deep into the pores of the metal where a brush can't reach, it removes rust as well. Rinse w/ water. I prefer acid over grinding as it doesn't thin the metal... and you're starting w/ thin metal to begin with.

If you've welded body sheet metal (or plated hardware) and saw the 'white feathers' in the air or had a white residue on the weld, that is poisonous to breathe and the weld will be contaminated. I use it for MIG and TIG (steel only) weld prep, you'd be surprised how much dirt and oxidation acid will burn out from an already clean looking piece of steel. See Weld Prep in Tech Tips.

Remember, if the lowest setting isnt low enough you can always move the ground clamp farther away.

Vigo wrote: Remember, if the lowest setting isnt low enough you can always move the ground clamp farther away.

also, you can use a 100 ft extension cord to drop the voltage as well.

Kj

I think the bodywork for this MiG ought to be duplicated:

Sorry, I just can't help a good pun every now and again.

I have two toes in the local welding community, and they rave for the most part about rosin core wire with no gas. I like the mix. that pure argon is what budget tiggers use on aluminum. when they apportion helium in it, theres no going back with aluminum. the mig with the mix gas should be okay if you stitch weld. tapping the trigger and letting it cool or moving like in spot welding should start you out. You can lay a 1/8" tig wire down and spot on that to avoid holes and getting close to the thin stuff will join it without voids. it will take practice--but most of life is like welding--just when you get good, youre done.

Picked up the Hobart 187 @ lunch, came home after work and put it together, set it up for .023 wire, set the knobs where the manual said to for 24 gauge sheet, hooked up some C25 gas, and started welding on some scrap. 10 minutes of that and I felt really comfortable with the machine. Move the whole operation from the workbench to the car, and an hour later I was done. Could not be happier with the purchase. WAY easier than TIG for a less-than-perfect environment.

I still love the TIG for a benchtop machine, and when stuff needs to be pretty, but I suspect this MIG is going to get used a lot. :)

+1 for the MIG

Mig is also great for speed or outdoor work with flux core. Need to fab something quick or fix something outside and it wins hands down.

Try to find a store such as http://www.mahanyweld.com/home.asp Those guys were great to my baja team. If you had a question not only would they answer it, they'd take you into the back room, set up some scrap and a similar machine to what you had and then teach you how to do what you wanted to do right there. Great people.

No other advice from me as I am quite bad @ the weldermafusing. The stuff sticks together but it looks like great amounts of chewing gum is holding it in place.

Avoid the flux core at all costs. For interior panels, floor pans etc, get an air puncher/flanger from harbor freight so you can do plug welds that simulate the factory spot welds.

My MIG was a cheapie Lincoln that came from Home Depot. Started life as flux core machine that I added the gas kit to make it a MIG. I've used it for all my FIAT rust removal needs:

For the exterior stuff I like to spend a lot of time fitting the patch panel for a perfect fit. I usually butt weld exterior panels where possible. Start with the lowest setting on your MIG. If possible get some scrap the same gauge as you are planning on welding to experiment on in getting the right settings. Get the settings so you can squeeze the trigger and weld for about a second to create a nice flat tack with good penetration.

I put a couple of tacks at each end/corner of the patch, then add a few spaced evenly. I don't work from one end to the other, instead I start in the middle an work my way out. I jump around a lot, to keep the heat from being concentrated in one area.

Hope this helps.

Yeah, I'll keep the flux core spool around just to save my ass if/when I run out of gas, but it is intended to be a MIG welder. I was actually able to do the zap-zap-zap tack welds in a line versus spacing them out like that. Of course, I wasn't concerned with warping like you would be on a visible body panel, but the heat control was such that I could just run a line of tacks like that without breaking thru.

I've been playing with my new Eastwood 135, using flux core until I get a tank (it came with the regulator). A few things are obvious:

The machine has potential.

Flux core IS pretty dirty.

I am not a natural-born welder.

I need more stuff.

Some clown in the Texas Panhandle started a grassfire with a grinder. The winds took it to a nasty level. Now we have constant warnings about any outside burning, grinding, welding, or anything else that might spark a fire.

I might have to roll the Saturn's corpse back out of the garage so I can practice without the self-appointed fire marshalls turning me in.

I was pretty stunned by the amount of sparks. Of course, doing overhead welding in a short sleeve shirt made me more aware of that than usual.

DILYSI Dave wrote: I was pretty stunned by the amount of sparks. Of course, doing overhead welding in a short sleeve shirt made me more aware of that than usual.

Yea, just a little different than welding barehanded, with just a mask.

Something tells me that you'll master MIG welding pretty fast. Most humans go from MIG to TIG and not the way you are going.

I learned to weld doing all the sheet metal on the tub/fenders/core support-valance of my '62 sprite. Not rusty, but lots mangled or missing.

• Wire speed can be everything when the going gets thin.

• if it's possible to to jog a flange on the edge of a patch so it's not a butt weld it's VERY helpful

• Be mindful of introducing distortion. Place tack welds far apart, let the part cool. Place tacks between tacks, let cool. Connect tacks w/ beads, etc.

• The copper backing spoon can be a lifesaver.

• A good 4" or 4-1/2" angle grinder w/ a momentary switch + a full range of flap wheels and Scotchbrite wheels and cut0ff discs is the other half of a MIG welder.

• Someone with any friends and a MIG welder should never need to buy beer. Add a small plasma cutter and/or a lathe and your Scotch habit should be taken care of as well.