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Why did I blow this hole through my frame while welding? [MIG]

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  • Why did I blow this hole through my frame while welding? [MIG]

    Hey folks, first-time poster, thanks for having me.

    There's a photo below.

    So I'm welding my relocated frame motor mounts on my Jeep's frame for an engine swap, and things are going pretty well. I'm a novice welder with maybe ten hours of practice, and countless hours of welding study & research under my belt.

    I'm welding with a 110v MIG, using 0.035" flux core (Lincoln Innershield NR-211).

    I stop welding to check out my progress, and for the first time, I see that I blew a 1/8" hole right through the frame! The frame is 1/8" thick. This has never happened before, even while practicing and intentionally pushing the machine to the limits (moving too fast, too slow, wire feed too fast, too slow, etc). I also had already welded the other motor mount with no issues.

    Click image for larger version

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    Any idea why this happened?

    I think the weld looks alright. What do you guys think? Is a second pass necessary?

    Cheers, -Alex.

  • #2
    frame weld hole

    Hello alex, I was wondering if the old mount was close to where you are installing the new one? I was thinking that maybe there was a very small crack in the frame, and dirt or very fine dust got into it? I can clearly see you did a beautiful job of prepping the weld area. I wonder if when the weld puddle was molten and if it went to a small crack like this the entrapped dirt or dust usually will melt and kinda explode out the puddle, like anything else it will take the path of least resistance. As far as the weld you put down it looks fine, you probably don't want to go much bigger than 1/8 of an inch fillet weld if the material the frame rail is only 1/8 inch thick. To fix that hole , and to do any more welding with out blowing through you could clamp a copper backing bar to the backside of the weld. This works as a backing bar(obviously) and also as a chill strip that helps conduct heat away so you don't blow holes in it.
    I have a welding addiction

    ...the only stupid question is the one you didn't ask


    • #3
      To be honest I probably wouldn't weld a motor mount on my vehicle with a 110v welder. There are a few possible reasons you blew a hole in the frame, incorrect electrode angle, spending too much time on the frame side of the fillet, wire speed too high...

      I don't spend a lot of time on gmaw or fcaw so I'm sure other people may have better information regarding.


      • #4
        Either to hot on the welder or ya hang ouy in one spot too long.


        • #5
          Either to hot, to slow or the frame is thin from rust on the inside in that spot. If it was me I would turn down the machine & weld verticle up.

          From the photo angle it looks like the weld does not have enough material. This happens by going to fast down because your trying to stay ahead of the puddle. Going up it lets you build up more material.
          Last edited by MMW; 04-28-2013, 11:25 AM.
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          Syncrowave 250


          • #6
            Would it have been possible to extend the motor mounts by welding on 1/8 plate flanges and bolted the motor mount to the frame. I was taught you never weld across a frame only length wise along the flanges . Looks as you were welding the frame got hotter and blew through.


            • #7
              If one can blow a hole in it then the machine has enough poop. I say great. Let cool start ahead of it and fill the hole and continue nice and hot just hanging in from burning thru, melting is a good thng. There is a lot of weld can go around there, you melt it thru like that a couple places here and there and the connection will be made.


              • #8
                My buddy has a late 60's Vette and his cross member welds look the same way. Weld weld, hole some more weld, hole. It bothered him so much he payed me to come over and weld up all the holes after he pulled the motor out. I too agree no 110v mig for that job, but thats just me...Bob
                Bob Wright


                • #9
                  Possibly over prepped the frame making a thin spot. Also I would weld this verticle up, and with only 10 hours welding under your belt I wouldn't even attempt it on such a critical part.
                  Miller syncrowave 200 runner with coolmate 4
                  and wp2025 weldcraft torch
                  Miller 125c plasma cutter


                  • #10
                    10n hrs or 10 days, the steel doesnt know any different, its melted together and likely over designed to start with, way more weld than it needs.