welding in replacement panels?

question:

When you guys weld in replacement panels, do you weld the entire panel in or just tack it in place then skim coat it with bondo?

Welded in my 1st patch panel last night (completely welded it in) and no matter what i did (MIG on lowest setting) it still seemed to warp i tad It won't be noticable once the skim coat is on there, but wondering if i may be doing something wrong?

EDIT: before i forget, i welded between 3/4" to 1", let it cool, then continued on until the panel was completely welded. The replacement panel is 16ga, and the wire is .030

 

I tack every 2 inches. Go around the panel tacking elongating each tack till it reaches the next tack. Basicly the idea is to go very slowly, after that I grind the weld clean and fill any holes by welding and grinding again. Sometimes it takes 3 or 4 times before the weld basicly disapears.

 

that's what i was attempting to do with the 3/4 to 1" welds......maybe i need to go the "tack, skip 2", tack again" route.

Still got 3 other panels to replace and a few small patches to weld in......guess i'll tinker with it a bit and go from there

 

Yeh if I ever show pics of Chia's replacment pannels( and that will never happen) you can see where I tried that short of a technique. My drivers side rocker has more waves in it then the Atlantic Ocean. By the time I finished with all my replacement panels I had learned to give more space between welds and to let them cool more.

 

The original panels were spot welded into place, not welded along the length of the seam. What I've seen mostly is punching the length of the seam and plug welding the new panel in place. Here's a link that gives some examples of plug welding and skip welding. http://www.autobodystore.com/door_rust.htm

 

thanx for that link Tim

I'm thinking i'll try just tack welding in spots and then working the spot welds back into one another.

Seems putting these panels in is going to take a little longer than i thought

 

I just tack enuff for it to feel solid and then smear it. Tring to get the weld to close causes to man problems.

 

Man problems? R)

I agree, just tack the panel in several inches apart and work your way around a little at a time.

 

Welding in baggy shorts can cause man problems too.

 

I might make mention of a technique I used with good results. In the last few years I've started using some clamps that I bought from Eastwood. They allow just enough gap to make for a good spot weld. I work from the outsides to the center. I spot weld to get as solid as possible then grind. This allows me to use so much less filler. I might also mention that my hammer and dolly is handy I've found it easier to flatten the ripples sooner better than later. Oh yeah I also make myself a heat barrier on the panel made out of newspaper soaked in water. This helps to isolate the heat and helps to disipate it. YMMV

 

BTDT (though soldering, not welding)

 

Wearing Vans tennis shoes is also not a good idea R)

 

jd7 how does that wet newspaper thing work? Never seen it done before, but have heard mention of it.

I had thought about keeping a bucket of water and a sponge handy to try "quenching" the area after welding........never tried that either though

Kinda glad this jeep isn't a restore job.....that way i can screw up, cover it up, and it's not much of a problem even though doing the job right is what i'm really after

 

The wet newspaper works as a barrier and a heat sink. Will slow the heat spreading to the rest of the panel.Thats especially helpful when you using a #000 tip and an accetaline torch to weld the panel. I use a mig now but the principal seems to work well for it too.There are welding paste out there commercially that do the same thing. This is way more economical. Be careful of quinching after welding, It can make it brittle if your not careful. Better too let cool slowly

 

The best way I've found to weld in a panel is to butt weld it in. (not lap weld) Unless you seal the back side of a lap weld, it will tend to attract mud and moisture. To hold the panel in place, I use magnets taken out of old computer hard drives. They're small and so powerful, you can't pull two of them apart. They will hold the two panels edge to edge very nicely. I leave about a metal thickness gap between the two panels. I weld in short sections as described above posts, allowing the metal to cool between welds. Since as the weld cools, the metal will tend to shrink and this is what causes the warpage you talk about. To counteract the shrinkage, after the weld is complete, I hammer the entire weld on dolly which will stretch the metal back into shape. You must weld the panel completely and not depend on Bondo (plastic) to seal the gap. FWIW.

tommy b

 

Never heard of using a large bar like this, but I have heard of flattening a penny and using it to back up welding small holes (like top mounting screw holes) shut.

tommy b

 

You can also use an aluminum chunk as a heat sink. Pro comp caster shims work well

You can also use compressed air to cool the spot welds.

 

Yeah, I wouldn't recommend putting cold water on a hot weld. That will make mild steel brittle, and someday it's liable to crack there. Heating and quenching changes the molecular structure of the steel.

In my machinist days, we'd harden steel by heating it cherry red and quenching it in a bucket of old used motor oil, not water.

We'd soften up things that were already hardened by heating them cherry red, then burying them in a barrel full of powdered lime, so they'd cool down really, really slow.

 

great idears fellas......never heard of the copper bar thing, but if i can find a chunk i'll give it a try