Gaps for sheetmetal welding

[DRJDVM's '69]

Okay, I've read and seen several different "opinions' on welding sheetmal when it comes to gaps between the two pieces.

I've been trying to cut and fit the pieces nice and snug together (very small gap, less than the wire diameter) and doing the individual tack/stitch weld technique. I was told that by having a nice tight fit, I would have less warpage issues....

Then other times I see people saying there should be a gap between the 2 pieces that is the same thickness as the metal you are welding. That just seems like a big gap to me when I'm working with 18-20 ga....... I guess the benefit is that the weld bead will be lower and require less grinding etc and insure full penetration etc...

Rihgt now I'm doing rust repair in future "hidden" areas but plan on doing fender patches etc, so I want to make sure that in the long run, I do it the right way for a good long term repair

[toxicz28]

The panel clamps use a .040" gap.

[Mathius]

Okay, I've read and seen several different "opinions' on welding sheetmal when it comes to gaps between the two pieces.

I've been trying to cut and fit the pieces nice and snug together (very small gap, less than the wire diameter) and doing the individual tack/stitch weld technique. I was told that by having a nice tight fit, I would have less warpage issues....

Then other times I see people saying there should be a gap between the 2 pieces that is the same thickness as the metal you are welding. That just seems like a big gap to me when I'm working with 18-20 ga....... I guess the benefit is that the weld bead will be lower and require less grinding etc and insure full penetration etc...

Rihgt now I'm doing rust repair in future "hidden" areas but plan on doing fender patches etc, so I want to make sure that in the long run, I do it the right way for a good long term repair

There's no right answer for this. Depends on thickness of material, wire size (or filler rod size), etc.

Mathius

[parsonsj]

One thing to remember is that welding will tend to pull the gaps closed. So putting in gaps will cause stress in the steel and tend to make the repair wavy. You have to weigh that disadvantage with the advantage that having a gap will allow better weld penetration.

My take: spend the time and get the panels perfectly flush. No gap. Use enough heat and stitch weld the sheetmetal with good penetration.

jp

[WGSPEEDSHOP]

welding 18 and 20 ga sheet metal. you want no gap. you are tig welding theses panels? if so you can use .035 mig wire and hammer weld the panels then file and metal finish....

Nick