Expansion

[clint78z]

I have welded in panels with the mig before, seemed pretty decent at it after a while. I used the lap weld technique because it didn't have to be perfect on my truck and didn't have the time. I had problems lap welding with the oxy/acyt, used screws to hold but the heat expaned the gap too big. It worked good when I could use vise grips.

Has anyone else had these problems, would it have worked better with a butt weld?? I was using #1 smith tip, I had decent flame control.

[anders nørgaard]

I have welded in panels with the mig before, seemed pretty decent at it after a while. I used the lap weld technique because it didn't have to be perfect on my truck and didn't have the time. I had problems lap welding with the oxy/acyt, used screws to hold but the heat expaned the gap too big. It worked good when I could use vise grips.

Has anyone else had these problems, would it have worked better with a butt weld?? I was using #1 smith tip, I had decent flame control.

Hi Clint,
What gauge were you welding? #1 tip would be about right for 16 ga. Lap weld or but weld, you'll always have some expansion. The screws should be very close to do any good (about an inch or so) Doing the lap weld, make sure to apply least heat to the "open/free" edge! Tack welding at 1" intervals would be more stabil. Tack....allow to cool.... tack..allow to cool....... "Adjust" gap between sheets to zero using hammer and dolly. Weld seem between two tacks, hammer and dolly. Adjust gap.... and so on and so on.

[clint78z]

It was pretty thin 18-20guage, I can't get a 0 tip for the torch #1 was the lowest I could get. I was trying to tack it right by the screw, it was expanding too much to fill with rod. Yes I was favoring the one edge to get it to work, seems like vise grips were the only thing that would hold properly. Mabey with more practice I could have pulled it off !! The dolly trick might have helped the cause.


Thanks for the answer, Clint

[Boogiemanz1]

Clint, when you start to lose it with the lap joint, you are in trouble. A butt weld lets you work the heat affected zone (HAZ the part that turns colors) and bring it back together. you want to get a quick tack and then skip a good distance and get another. If you are having a problem with the tack, make sure that your filler metal (rod) is the same thickness as the metal. Skip around until you have tacks at least every inch. You can actually weld the whole part with just a series of tacks if you keep at it


I would get a couple of small pieces of the metal you are going to use and practice on them first. If the gap begins to open, hammer on the HAZ of the tacks you have made until you can bring it back. Practice is the only way to learn this.

Dutch did a post about hammer welding recently, find an read that there is some good info there.........................john

[clint78z]

I think next time I try, I will go with butt joint.

I was tack welding, I would heat about an inch from the screw. By the time I got a nice glittery puddle, the gap would open up 1/8". I tried using .035mig wire but seemed very floppy, and couldn't direct it. Coat hanger wire seemed to work better, it fused pretty well on the test coupons. What do you use for filler rod ??

[Bob Baisden]

If the gap begins to open, hammer on the HAZ of the tacks you have made until you can bring it back. Practice is the only way to learn this.

John, if your tacking from one side to the other, hammering on the adjacent tack will make the gap wider ??

Bob

[Tisdelski]

hi bob,
i think the gap he is describing is a misalignment gap that will tighten up as the tack is planished flat, not the actual gap if the panel is flat. hard to describe, easy to see.

gary

[clint78z]

Yes you got it RodDoc, the overlap buldges away when heated. I borrowed the mig from a friend to try, I only have the torch now, it has a little more learning curve.

Picked up some great tips from everyone, next time around I will use a butt weld.

Cheers, Clint

[Tisdelski]

hi guys,
i guess i missed the fact he was welding an overlap, not a butt weld.

gary

p.s. i`ll learn to read soon.