Welding patches into body...

[pies]

When welding patches into bodywork, do you need to weld right across the join between patch and the rest of the panel? or are regular evenly spaced spot welds ok?

[Unclejake]

You have two problems.

Heat and moisture.

To stop moisture getting in a full weld is prefered but the heat this creates distorts the panel badly and gives you a headache later on when you try to get the body straight.

Are you using a MIG?

[Brock-Lee]

A guy was telling me to mig patches in with heaps of spot welds so it formed one continous weld. And between each weld you cool it off with an air gun. Tis what I have done in the past and seems to work fine

[QCADTA]

dunno bout anyone else but i used my mig on a higheramp setting and went in short bursts connecting the dots as mentioned above, seemed to work alright, but havent had my car out in the daylight yet

[pies]

yep using gas mig. have majorly distorted one of my gaurds after doing small spots to hold patch in place, then spotting around the join to fill it in. wonder if just leave it to cool more between spots... mind you, i have no idea how the welder is set up. none of the little pictures on the front make any sense lol

[forced]

I'm in the middle of doing mine at the moment too except I don't have a mig, I'm using oxy acetylene. All the "experts" say you can't do it that way , so that's the way I'm doing it.Well that's because I've got oxy acetylene

So long as your patch is a perfect fit, you do small tacks, let them cool, hammer & dolly them, do more tacks, repeat, repeat, you don't get distortion. That's on flat panels.Curved panels aren't a prob. It's just really slow.Eventually you'll end up with a continuous weld.

A mig is supposedly so much easier but I've never used one.

Where's VVV whan he's needed?

[cute wee gem]

I use this site sometimes, have a look as its got panel work and all sorts of stuff.

http://www.mig-welding.co.uk/

[esky 73]

if you look at my project thread you can see what i did on the front, as above, good fit, tack in, hammer and dolly, what happens is when you weld it expands then as it cools it shrinks, problem is it shrinks more than it expands creating distorsion, theres probably a million ways to go about it but what worked for me was low amps, and spot welding, cooling as i went and hammering out, hope that is some help,

[ZedHed]

keep a bucket of ice and rags next to you,cool off each weld and move around the patch,like bolting a head down.

You dont need to run a bead.......small spot weldes are ok.

[Hemi]

a ggod idea is to also put somthing big and heavy next to what you welding to suck all the heat up . it works , even like a big speaker magnet works well

i dont like the idea of water and rags being around cause they cause a big temp drop in very little time .

then again ive never done panels on a car so i cant really comment

[ZedHed]

its the same principal as cooling down shrink spots...when you have a dent that wont "sit" right,heat it up in the inner most part of the dent shrink it with your hammer and file then hit it with a wet rag,doesnt have to be ice cold...depends on the shape of the panel and how big/bad the area to repair is.