Auto body repair with MIG how to.

admin

I've been getting a ton of good information from this site so I figured it was my turn to contribute. I've seen a few threads asking about MIG for auto body so here's a little how to. Repair was completed with a Miller 211 running on 120v using .023 wire. This truck had a cheap lumber rack mounted to it, and between some heavy loads and rough roads it basically annihilated the bedrail.First step was to clean everything up, clamp it in place and plug weld the skin to the bed structure (didn't get any good pictures of the plug welds). Also notice the holes drilled at the end of the cracks to prevent further crack propagation.I started lining everything up and tacking it in place.Notice the tacks are fairly flat, this is important as it minimizes the amount of grinding needed once fully welded. It takes a while to get dialed in just right, with a proper setting your tacks will be flat with good penetration, they should look the same front and back.The top of the bedrail was pretty mangled, there's a little piece missing even.Straightened a little more and patch panel made...And top all straightened out and patch panel installed. All tacked up and ready to fully weld.I got in a groove when I welded her up and sanded it down so I don't have any in progress pictures of the full welding portion. This is everything welded and sanded, with a little bit of work with the hammer and dolly to take care of the shrinkage from heat. Finished product is ready for high build primer with no plastic filler needed.Any questions are more than welcome.Last edited by Sharon Needles; 03-30-2015 at 06:01 AM.
Reply:Looking very good you may get by with just primer surfacer.
Reply:Beauty repair Sharon nice job man. I wouldnt mind being able to do that good a job myself one day. Im gonna ask..When you go to lay your bead do you run over the tacks or stop at them? If not, what would the best way, or the way you did it in regaurds to the final bead. Did you skip over every other spot weld to keep the heat down? To me it looks as good as new and something my little H.H.125 can handle. Nice job on the little patch piece as well....My bad one more question, when you do your patch, do you get it as tight as possible or do you leave a 16th or 32nd of a gap or is is just eyyball it? Sorry for the questions, but you said ask away  Once again clean lookin repair, keep up the good work.Pidge.Lincoln210mpHobart Handler 125...soldBoat battery and a couple coat hangers
Reply:I don't ever run beads, it's all just single tacks as far away from each other as I can get them, just bounce around until you've got it fully welded. I wait until an area is cool to the touch before putting another tack down.  Your 125 is perfect for auto body. When I make patch panels the fitup depends on whether or not I can get a copper backer behind the area. In this case I wasn't able to so I fit the patch as tight as possible, but if I can get a backer in I'll leave an .024-.035 gap all the way around for better penetration.
Reply:Originally Posted by Sharon NeedlesI don't ever run beads, it's all just single tacks as far away from each other as I can get them, just bounce around until you've got it fully welded.
Reply:Nice job there. Just a couple welders, big hammers, grinders, and torches.Work will free you.Men in dirty jeans built this country, while men in clean suits have destroyed it. Trump/Carson 2016-2024
Reply:Ahh good to know. I didn't realize it was tack,tack,tack to fill it, at the same time I was wondering how else would ya have gotten the "straight" results by running a full bead. I understand completely what your saying and it's good to know that the ol 125 is a good choice for this. I get the whole tack,tack,tack on the surface, but is there any reprocussions on the back side at all? I really dont know and to me the logical thing to do is...if you can...primer the underside or protect it with a rust inhibitor. You've done a good job by the looks of it I'm just trying to learn a thing or two. Pidge.Lincoln210mpHobart Handler 125...soldBoat battery and a couple coat hangers
Reply:It's a bit of a challenge, but if you mess with your machine settings enough you'll be able to get a nice flat tack that will look the same on both sides. I overlap my tacks a little bit rather than spacing them apart, it helps ensure you won't get pinholes that you have to go back and fill. Patience is the key here, keeping your heat down is a must. You'll never get away from having to get out the hammer and dolly to stretch out the metal after the welding and sanding, but if you get too carried away and put too much heat in the panel you'll have a nightmare on your hands. Thanks everybody for the kind words.
Reply:Great looking repair, thanks for posting it!You do very nice work.2 Hobart MIG welders, 1 on the gas 1 flux coreHTP Invertig 221 DV Eastwood TIG200HTP MIG 2400
Reply:Originally Posted by massacreGreat looking repair, thanks for posting it!You do very nice work.
Reply:Very good repair...put too much heat in the panel you'll have a nightmare on your hands
Reply:Sharon, were you using a mig machine that has a tack/spot weld function?  Using a special  nozzle?  I was wondering because my Fabricator 210  has the spot weld and stitch timer function.  I haven't tried it yet but have noticed there is also a special nozzle offered to support spot welding and stitch.  Welcome.Jerry30+ yrs Army Infantry & Field Artillery, 25 yrs agoMiller 350LX Tig Runner TA 210, spool gunLincoln 250/250 IdealArcESAB PCM 500i PlasmaKazoo 30"  vert BSKazoo 9x16 horiz BSClausing 12x24 lathe20T Air Press
Reply:Originally Posted by RussZHCVery good repair...just like to add, don't assume even for the same thickness of panel, that the same amount of heat will have the same effect, it makes a huge difference if you are working in the middle of a large panel, if you are on a character line that moves deeper or a character line that moves "towards" you, as in the second photo.  I've had that nightmare on several occasions where it just kept getting deeper and deeper.If I am not mistaken, that is a Ford?  In a long past life worked at a dealership and found the way Ford did those stake holes was all over the map, some great, others like they had barely rolled and crimped the panels into the "hole".
Reply:Nice tutorial, thanks for posting it.If you don't want to stand behind our Troops, feel free to stand in front of them.
Reply:Thanks for posting this, Sharon.Do you perform any prep work on the back side of the metal?I have a lot of sheet metal work to do on my Triumph - I did it before using the oxy-acetylene torch and a 000 tip, which worked OK but always warped / shrank a lot.  Looking forward to finishing the job with the MIG or TIG welder.Most of my repair is to deal with rust so I expect it to be much more involved than just damage, since I'm sure it is worse than it looks.
Reply:Normally I'll take the backside of the repair area down to bare metal as well as finish sand it out. I didn't have the ability to on this project as the backside of the welds were blocked by the stake pocket.
Reply:Most of my repair is to deal with rust so I expect it to be much more involved than just damage, since I'm sure it is worse than it looks.