Butt welding panel gap size?

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PostPosted: Sat Aug 28, 2021 4:45 pm
Doright wrote:
chopolds wrote:I try to fit it up for no gap. Can't see the advantage to any sort of gap, if your welding is good.

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Zero GAP! Not with Thin sheet metal
And if I may add while some advocate and accept Mig welding as acceptable.
GAS welding or Tig is the preferred method in my opinion especially for panel repairs.

When gas welding OR Tig welding its completely possible and Preferred to fusion weld the two pieces together with NO filler rod when you have ZERO GAP which is the best in my opinion.

Why is Tig the best?

I'm a newbie at welding. All I have is a Mig.

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PostPosted: Sun Aug 29, 2021 5:01 am

You can actualy run a Bead with Tig and Gas on sheet metal, Mig not so much.
Mig is a More Zap zap zap deal its more like spot welding its just too hot.
Gas and Tig weld bead is much softer more malleable when planishing.

Mig bead will crack when Planishing

Gas hammer welding, The right way to do it
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PostPosted: Sun Aug 29, 2021 7:55 am
Not entirely the truth. More like an urban myth. WHenever you heat metal up, when it cools, it will shrink. Even at temps less than welding. SO when you weld, the metal at the seam shrinks, and to get it back to it's original shape, you must stretch it. Using a hammer, ON dolly does this. But it takes a practiced hand to get the right amount of stretching done. MIG welds do not lend themselves to easy stretching, due to it's harder weld bead, and excess material deposited at the seam. That is why TIG and gas are better. Softer weld beads, and less, if no, deposited material at the seam.
I find having a gap, make me stay longer at the weld seam, which puts more heat into the panel. Or, if you don't get the wire fed exactly in between the 2 pieces of metal, it goes to one side, and makes a hole.

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PostPosted: Sun Aug 29, 2021 9:16 am
I have a gas MIG that I use for most of my welding. The .023" wire works the best for sheet metal in my opinion.

With all welding, practice is necessary. Watching videos on how to set the welder up will help, but until you get the technique down you will struggle at first.

Get metal the same thickness you have on your car, learn to spot weld first. Knowing what a good weld should look like, the color and the penetration are key.

I like to spot weld my patches in place, planish each spot, then do another set of spot welds and repeat the process. Eventually you will have very small distances between your spot welds that are easy to connect without over heating the metal.

Zero gap is always the goal for me.
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PostPosted: Sun Aug 29, 2021 9:45 pm
The new metal I want to weld is thicker then the original

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