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Spot Welding with MIG

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  • Spot Welding with MIG

    I'm new to the site and have a question on Spot Welding with a MIG. I have a Miller 252 with the std. M-25gun and have been welding for about two years now. I need to do a lot of automotive sheet metal body part welding as a hobby (restoring my old car) and need some advice on doing "spot welds" with my MIG machine. Most of the steel I will be spot welding will be approx. 18 and 22ga.
    In doing "floor pans" in an older car, I have had a problem with burn through and irregular shaped welds, I think mainly because of inconsistency of thickness in the original sheetmetal due to prior corrosion, etc. I've tried moving in a circular pattern when doing the welds, but have had a hard time getting nice looking welds. Some good, some bad. I plan to order a spot weld nozzle. Maybe that will help?? I'm not sure of the "best" settings for voltage and wire speed and need some help. I could use some basic "tips" on the correct way to do a MIG spot weld, settings to use/try, methods, etc.
    Any help would be appreciated.
    Thanks. Harold

  • #2
    whenever I've done spot welds on a floor pan or auto body. I overlap the two pieces and punch holes about 5/16" in the top piece than just do a simple spot weld (correct stickout and gun angle than pull the trigger for a second or two) until the 2 pieces are welded to each other and the hole is filled nicely pretty flat. I usually run about 14- 17 volts and 200-220 ws. turn it down a bit more if that is to hot and your getting burn through.
    Miller syncrowave 200 runner with coolmate 4
    and wp2025 weldcraft torch
    Miller 125c plasma cutter

    Comment


    • #3
      okie,

      If you have access behind the panels you are spot welding together, get yourself some copper plates or a copper plumbing cap to back up the hole and fill in the welds.

      I have and assortment of different diameter copper pipe caps with short pieces of pipe that I use a vicegrip to hold in place. I also have a couple of panel welding pliers that have a copper paddle on one side and the opposite end is forked and open around the hole to not only clamp the panels together and provide a backing to fill in the hole with weld. Finally, I bought a couple of pieces of copper sheeting in 1/16" to 1/8" and cut them into different shapes of strips and triangles and use them as backing, to fill in welds in impossible areas.

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      • #4
        you can also buy spot weld vise grips that have a copper backing plate if your doing spot welds on an accessible edge.
        Miller syncrowave 200 runner with coolmate 4
        and wp2025 weldcraft torch
        Miller 125c plasma cutter

        Comment


        • #5
          it takes more heat to burn the paint off than melt the steel, make sure both sides of the weld are clean, if you get it hot enough, the crap on the back side of the weld can be sucked into the weld ,pin holes, burnthru,s ect god luck

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          • #6
            okie, Your MM252 has timer functions you would set to get the best spot weld results for particular materials. You set them by trial and error until you become familiar with what works and then tweek from there. If you're welding two different thickness materials you would weld from the 'thin' side.

            Timers to set would be Preflow, Spot Timer, Burnback and Postflow. For the best results you'll have to do some test settings on like material that is to be welded. Yes, you want to get any spot weld nozzles you feel you would need (straight, inside corner or outside corner) as they will allow for the consistancy you are and should be looking for.
            MM200 w/spot controller and Spoolmatic 1
            Syncrowave 180 SD
            Bobcat 225G Plus LPG/NG w/14-pin*
            *Homemade Suitcase Wire Feeder
            *HF-251D-1
            *WC-1S & Spoolmatic 1
            PakMaster 100XL
            Marquette "Star Jet" 21-110
            http://www.millerwelds.com/images/sm...rolleyes.png?2

            Comment


            • #7
              Spot Welding with MIG

              Thanks for the info. I tried to buy the flat spot weld nozzle for my 252, but Miller tells me it's discontinued. Do you know of anyone that carries these spot nozzles for my machine, or of a place that carries obsolete or discontinued Miller parts?

              Many Thanks.

              Comment


              • #8
                Okie, You could also Pop Rivet the floor pans .

                ............ Norm
                - Arcair- K 4000 CAC.
                - LN - 25
                - Lincoln Ranger 8
                -DeWalt Compressor

                www.normsmobilewelding.blogspot.com

                Comment


                • #9
                  okie, I suggest you check with forum member weldersales (Larry Burross). If he doesn't have any he may know of a source.

                  If not, I would look at building your own using a standard nozzle as the basis. Slip a piece of appropriately sized copper pipe over, cut to length and shape the end accordingly for a straight, inside or outside corner. May have to turn down the standard nozzle OD or bore the pipe ID to fit.

                  May be able to adapt another brand (Tweco, Bernard, etc) to fit too.
                  MM200 w/spot controller and Spoolmatic 1
                  Syncrowave 180 SD
                  Bobcat 225G Plus LPG/NG w/14-pin*
                  *Homemade Suitcase Wire Feeder
                  *HF-251D-1
                  *WC-1S & Spoolmatic 1
                  PakMaster 100XL
                  Marquette "Star Jet" 21-110
                  http://www.millerwelds.com/images/sm...rolleyes.png?2

                  Comment


                  • #10
                    Using a MM251, whenever we have to "weld" EMT tubing together to make a light duty frame or something (not my idea, just projects some of the school staff give us), we just use the mig and "spot weld"/ pull the trigger for a second and MAKE spot welds every 1 inch down the area neede to be welded. Then go back and spot 1/2 way of between those welds. Then go back and spot in between those welds. Then go back and spot between those welds. Do it until they are all connected. Once all those spots are all connected, then you can put a bead over that, because they is enough metal built up.
                    have fun
                    I'm not late...
                    I'm just on Hawaiian Time

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                    • #11
                      Thanks to everyone for the great advice! I don't know if I had mentioned that I was using .035" size ER70S-6 wire. Would it help me to go to the next size down (.030") wire? Would that significantly help the "burn through" situation?
                      If I will be doing floor pans, and thin sheetmetal for some time, should I look at going to .023" wire (if my machine will accept it?)? I think I may have to change a "liner"?? with .023"??
                      Thanks for the help!!

                      Comment


                      • #12
                        I don't work with 18-22ga sheet metal very often but yes, .030 would be better and .023 even better IMO. I've used .030 on 16ga but .023 is more 'forgiving' and easier to control for me.

                        If it's just a quick job I'll just leave .030 in the machine if that's what's in it at the time but if I were to be doing a lot I'd change over to .023 - but that's me.
                        MM200 w/spot controller and Spoolmatic 1
                        Syncrowave 180 SD
                        Bobcat 225G Plus LPG/NG w/14-pin*
                        *Homemade Suitcase Wire Feeder
                        *HF-251D-1
                        *WC-1S & Spoolmatic 1
                        PakMaster 100XL
                        Marquette "Star Jet" 21-110
                        http://www.millerwelds.com/images/sm...rolleyes.png?2

                        Comment


                        • #13
                          Great Info. Duane! Again, Thanks for your help. I think I can take it from here....we'll give it a try.:

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