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MIG on subframe connectors

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  • MIG on subframe connectors

    I've done SFCs before. Mostly TIG, sometimes a combination of TIG and stick (big gaps).

    I'd like to MIG in a set. Assuming all the welding will be done upside down, and the floor boards / existing frame are 16 gauge steel, the mounting plates are 3/16.

    In the past we would grind down the 3/16 to about a 1/16 edge (about a 45-60 bevel) and spot weld all the way around (mostly to keep things from burning down).

    Its more or less an upside down lap weld, with a thin piece on top and a thicker piece on the bottom.

    Can someone give me an idea what gun angle to try and heat settings.

    I'm guessing I setup for the thinner piece and just wet in the thick stuff, but I'm worried about it going down cold. If I setup for the thick stuff and start the weld on the edge of the 3/16 plate, I run the risk of the weld dropping out and not even touching the floor boards.

    So questions:
    1) Set the heat for 3/16, or the 16 gauge or somewhere inbetween.

    2) Gun angle?

    3) Start the wire on the 3/16, the 16 gauge, or right at the gap?

    4) How long of a bead can I run? 2", 1" before it needs to cool.

    Last question,

    Has anyone tried the pre-welded SFCs from Global West. I've installed them in the past but welded them completely myself. If the fit is tight, I don't mind paying extra to be that much farther along.
    Part 929C is what I'm interested in.

    Thanks in advance.

    BTW, "screw it and TIG it" is a valid response - just sometimes the gaps are large enough that TIG doesn't seem reasonable.
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  • #2
    I have done many sets on mustangs, I have a hobart handler 135, I crank up the amps to max, wire feed around 3-4. I do it all as spot welds stacked. This is how I was taught to weld auto body, you set it hotter then if you wanted to run a bead and you spot it. You get good penetration and it burns hot enough to burn off paint and contamination that grinding and sanding might not take off.

    I the only prep I do it grind off the paint and undercoating off the bottom of the car and clean up the weld area on the sub frames. No need to grind the edge down or anything like that. I keep the angle at what ever works (your not running a bead) and keep thw wire on the existing weld (once one is established). I always get plenty of burn in on both the sub frame and the car.

    Whether this is right or wrong I do not know, this is just how I have been doing it for 12 years.

    Last edited by engnerdan; 04-15-2010, 08:57 AM.
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