Thin metal blowing through

  1. Lofc2909 New Member

    Messages:
    3
    Location:
    England
    Hi - first post have recently started welding as am restoring an old jaguar. Using a GYS smart mig all set up fine and have been practicing 1mm sheets using the thin metal method.

    This works fine on a welding bench and I’ve done quite a few decentish welds using this method however as soon as I do my first piece on the car itself using the same thickness sheet, I’m blowing through almost immediately on both pieces.

    I also seem to be struggling getting a decent earth - am clamped to a freshly ground to bear metal sill which is part of the workpiece but after a few mins work, there’s little power in the welds.

    Any advice really appreciated.
     
  2. Lofc2909 New Member

    Messages:
    3
    Location:
    England
    Forgot to mention using .6 wire
     
  3. Alf98

    Alf98 New Member

    Messages:
    15
    Location:
    United Kingdom
    Can you get some aluminium behind it to help spread the heat ? As for the earth I’m not too sure
     
    stuvy and Rig Pig like this.
  4. Rig Pig

    Rig Pig Member

    Messages:
    3,368
    Location:
    Narrwich! U.K.
    I use an old copper buss bar as a backer on thin steel, it makes it so much easier.
     
    julianthegypsy, BarrieJ and stuvy like this.
  5. Alf98

    Alf98 New Member

    Messages:
    15
    Location:
    United Kingdom
    Also if the clamps in a poor condition this won’t help, check for loose connections or damaged parts
     
  6. daedalusminos Member

    Messages:
    510
    Location:
    Norwich
    What type of weld are you attempting, I'm guessing butt weld? Post some photos of your bench work and your car work so we can see the problem.
     
  7. stuvy Member

    Turn the heat down if poss

    Don’t try and weld a run of 6” as thin stuff will get too hot and then blow throw
     
  8. Paul.

    Paul. Moderator Staff Member

    Messages:
    5,860
    Location:
    Northampton. UK
    If you have a poor connection on the return clamp you'll never get proper control of the arc, clamp a mole grip onto a bare metal part of the car and connect the welding return clamp (its not an earth) to the mole grip, personally I prefer 0.8 wire for thin rusty stuff it puts in more metal and fills gaps better.
     
    RonA likes this.
  9. earthman Member

    Messages:
    473
    Using an heat sink of some sort, great idea!
     
    Alf98 likes this.
  10. Lofc2909 New Member

    Messages:
    3
    Location:
    England
    Sorry been out all day no pics of work -it is butt welding though. Will try heat sink and see if that helps. Will report back.
     
  11. Mattycoops43 Member

    Messages:
    97
    Location:
    Newport, South Wales
    Are you definitely back to proper solid metal on the car? if you don't do enough cutting back, you could be welding to 0.8 or 0.6 metal which is much harder.
     
  12. slimjim Member

    Messages:
    770
    UK Cumbria
    I use a piece of 22mm copper pipe flatterend at the end and into a slight curve, that way I can hold it at the back of the weld, to absorb some of the heat, then effectively tack weld until it’s fully welded, using the copper behind any holes, if the metal is too thin though, you might as well cut out and replace with fresh.
     
  13. julianthegypsy Member

    Messages:
    2,627
    Location:
    Cirencester
    I find a rag damped down and twisted into a ball helps cool things down when this happens. Starts off fine and gets worse is often because everything is getting hotter. Dab it with the rag and it goes back to normal .
     
  14. Morrisman Member

    Car bodywork, I tend to use a series of tacks, one after another. Better welders might make long runs, but it never worked too well for me.
     
    Mattycoops43 likes this.
  15. Mattycoops43 Member

    Messages:
    97
    Location:
    Newport, South Wales
    Yes, spot on. The way I used to do it, was a 1 second on, 2 off kind of action, (or thereabouts) rather than leaving lots of gaps between separate tacks. Makes for a much neater weld. Obviously I don't mean I didn't tack stuff in place first to stop warping, I mean when you have it fixed and want to join it in. Basically, do a few mm, then wait till the orange glow disappears.
     
    julianthegypsy likes this.
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