Auto body lap weld ( both sides )

[Joeyg]

So just a quickie you can never go wrong ( wink wink ) I’m restoring a car at the moment struggling as the metal is 0.8mm in some places. Would a lap weld be a good standard if the lap is 4/5mm then tack welded with good penetration from both sides ? As surely any of the sealed area between the two sheet pieces is going to be fused as such. Many thanks

The sheet in the pictures is not finished needs to be trimmed down etc and beating feathered/smoothed

 

[mr haynes]

Firstly, it will depend on if it is structural or not. Yes and you need to replace like with like. i.e. cutting into a solid piece needs replaced with a continous weld not stitched.
Spot welds do not need to be replaced with seam weld.
A lap joint is fine if it meets your requirements and conforms to what i've said above.
Ideal world we butt join every plate being let in but not always practical

 

[Joeyg]

No obviously I know there needs to be a continuous weld I think I may of worded it wrong , many thanks for your reply. Hopefully I will get the chance to work on it at the weekend/ next week , so I will post some pictures.

With a butt also n very thin metal can you essentially weld without a gap and literally butt them , I’ve tried using the clamps with a pre set gap on thin stuff and it didn’t happen , soon as my wire touched instant hole

 

[chrismac]

I was going to reply earlier but never as I am no expert in body work repairs, if possible you could butt and have a backing strip of copper, that way you wont blow holes, even if its just a short piece which needs moved frequently, no need to gap that thin material, there will be gaps when the fit is not exact I would guess, again the copper strip would help here (if its possible)

 

[mr haynes]

When it comes to welding thin steel you have to think of it as a series of tack welds that become countinuous rather than running a bead.
It may be your welder isn't set low enough to easily accomplish what you are trying to do.

Fitzee's Fabrications on youtube is always a good source for bodywork techniques and ideas

 

[Joeyg]

Yes I know that , set them an inch apart ( then graduate how far you do the next tack so as to mitigate warping )and heat. cool it down with an air line. Use copper as a backing to suck up some heat. Thank you for the advice though my friend

The problem is my welder only has six voltage settings , BUT I have just purchased some 0.6mm wire as I have been using 0.8mm , so I will see if that makes any difference. Problem with the 0.8mm is I can only get the penetration and width of puddle I want once I’ve done 2 or 3 tacks. So hopefully with using a thinner wire it should mitigate that problem

 

[Joeyg]

Or I will just burn through on the first tack and have a nervous breakdown

 

[Domdom]

Have a look at this. Butt welded in 2 inch sections, thick copper block backing it up. 0.8mm, 28 amps.

Post in thread 'Sierra XR4i full restoration.'
https://www.mig-welding.co.uk/forum/threads/sierra-xr4i-full-restoration.111673/post-1913733

 

[RWD3M]

Have a look at this. Butt welded in 2 inch sections, thick copper block backing it up. 0.8mm, 28 amps.

Post in thread 'Sierra XR4i full restoration.'
https://www.mig-welding.co.uk/forum/threads/sierra-xr4i-full-restoration.111673/post-1913733

Which reminds me, any progress of late?

 

[Domdom]

Which reminds me, any progress of late?

No Sir, too much paying work going on.

 

[optima21]

you can butt weld thin metal with a MIG, here's my way of doing it, without any backing strips. its a case of keeping the heat to a minimum.

minimising distortion when mig welding thin steel

here's my way of doing this, on a doorskin and welding in a new bottom edge from 0.9mm zintec. When Mig welding thin sections I prefer not to have a gap between the sections and to get them touching if possible. I'll start off by welding a few tacks along the length. the tacks will shrink when...

www.mig-welding.co.uk

 

[Burdekin]

Use 1 to 1.2mm for your patch and weld towards the thicker metal.

 

[Joeyg]

This was the first try previously the first few spot welds came out exactly how I wanted , then I got some cold lap. Which equates in a not so pretty uniform weld.

 

[addjunkie]

This was the first try previously the first few spot welds came out exactly how I wanted , then I got some cold lap. Which equates in a not so pretty uniform weld.

View attachment 426329

There is far worse than that often presented for MOTs by paid professionals.

 

[Joeyg]

There is far worse than that often presented for MOTs by paid professionals.

Ah that’s handy to know I just have very high standards, fortunately I’m starting night school for tig in feb 24. So can hopefully get doing thin stuff with greater accuracy.

 

[Tupers]

This probably isn’t the answer you want but you probably just need more practice off the car. Your welds above look good you I think you just need a little more time to get your eye in.

Trying the teach yourself on the final product is a recipe for disaster and disappointment.

I’d also say I would not recommend cooling tac welds or any welds with an air line. Although on the surface it seems logical to stop heat spreading into the rest of the panel cooling tacs can result in “pinching” and distortion in the panel.

I’m my experience with TIG and MIG on body panel you’re better served letting them heat and cool naturally. You will get some distortion whatever you do but it’s best to avoid multiple heat cycles.

Even TIG at 30A with .8mm filler requires planishing if you want really flat repairs.

 

[Joeyg]

Thanks for the reply , yeah I think I will have a good session on sone long scrap lengths and try dial my welder in , essentially it’s not a difficult weld for the most parts but as it gets inside the inner wing it DOES become a ducking pig to be able to see and get the gun in.

And you are 100% right , there’s nothing worse spending hours making a new piece only to blow holes through it and relegate it to the scrap pile

 

[RWD3M]

Only just remembered this! You could do a lot worse than give this a watch:

It's a Retropower butt welding tutorial.

Nat goes on a bit but he's very thorough.

 

[Joeyg]

Thank you sir I shall give it a good watch !

Only just remembered this! You could do a lot worse than give this a watch:

It's a Retropower butt welding tutorial.

Nat goes on a bit but he's very thoroug

 

[Joeyg]

Thank you sir I shall give it a good watch !

Bloody good video , this chap is anal as **Language** ( ahem ) but no seriously good video , the standard is very very high