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Undercut help & tube welds--vertical up, thick to thin

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  • Undercut help & tube welds--vertical up, thick to thin

    This is hopefully an easy question!

    I've been practicing uphill, butting an 11g (~1/8") tube horizontally up against a vertical piece of 1/4" (it looks like this: ==|...don't ask, not my design, but that's what needs welded). I'm starting the bead at 3:00 and working up to 12:00.

    Now and then I can see it undercut on the 1/4", usually right around 1:30...material just falls away.

    I'll be practicing more tonight. Do I just need to spend a little more time depositing material on the 1/4" side?

    Another question...I've been practicing horizontal tube to tube welds, running four beads with four tacks, like this...tack at 1:30, 4:30, 7:30 and 10:30, then weld uphill from 3:00 to 12:00, 6:00 to 9:00, 9:00 to 12:00, and 6:00 to 3:00, grinding out each tack before I run the bead.

    I'm not sure I like the heat profile I see on the tube, doing that. I still need quite a bit of practice before I can run two beads bottom to top. Would it be better to grind out the first and last bits of the first welds, then run over the "cooler" parts (not cold lap as far as I can tell) with the end of the new welds?

    Am I over-thinking this?

    Thanks much,
    Sean

  • #2
    process, settings?
    Bobcat 225NT
    Cutmaster 52
    Lincoln Weld-Pak 100 buzz box
    Caterpillar TH63
    '07 Kawasaki ZZR600

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    • #3
      No mater the process. For undercut the answer is the parent metal has been eroded away by the arc or heat source and not filled back in with the filler so stop eroding the parent metal away or fill it back up before you move on with the puddle

      Thick to thin concentrate the heat on the thick and allow the puddle to wash into the thin.

      A test to see the penetration into the thin would be advisable.

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      • #4
        Originally posted by FATFAB View Post
        No mater the process. For undercut the answer is the parent metal has been eroded away by the arc or heat source and not filled back in with the filler so stop eroding the parent metal away or fill it back up before you move on with the puddle

        Thick to thin concentrate the heat on the thick and allow the puddle to wash into the thin.

        A test to see the penetration into the thin would be advisable.
        FATFAB: Excellent reply. Normally, filling in before moving on is a matter of slowing down a bit. Assuming all else equal.
        Geezer
        Miller 175
        Power MIG 255c
        Ranger 8
        1974 Wisconsin 5K AC Only (Cherry)
        Spool Gun
        185 TIG
        Victor/Harris O/A

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        • #5
          Thanks for the tips, will make a few practice beads and (gulp) post a picture.

          -Sean

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