Newbie boy..... Lap welding/car body

[Scott Stephen]

Hi all.

Ive just bought my first welder (Sealey SuperMig 150).. Ive been practising on 0.8mm steel with 0.6mm wire at the lowerst setting, my results are mixed...
I have a couple of questions for the experts..


1. On the practice sheet im getting a clean continuous weld if i dont move the torch in an arc/zig zag... but as soon as i attempt this technique the weld splatters badly/breaks up or in some cases burns through. Ive tried the machine on low and higher settings but im struggling to master it

2. Lap welding car body panels - I presume the torch has to be pointing directly at the joint? - Do i just work my way up the joint (short burts for thin metal) in a side to side fashion from lower plate to higher plate just like the butt weld technique in short bursts on the video tutorial? - Ive tried and failed LOL

3. Is it at all possible to get a clean continuous weld on car body panels or is there just too much risk of blow through? - My machines lowest setting is 30A appparently. Ive seen pictures on the net of folk spotting all the way down a panel, but it does look a bit messy.

Ive bought an old Austin Metro.... so there is plenty of welding practice ahead of me

Thanks guys

Scott

 

[BillJ]

The trouble with a continuous weld is that even if you manage not to burn through, the heat build-up in the joint and surrounding metal will cause severe distortion in such thin sheet and it'll look a right mess that no amount of grinding or sanding will sort out.

A good technique is to tack at intervals, one at one end, then the other, then the next at the first end, etc. Then do some more tacks between, still spreading the heat from one side to the other. Then when the tacks are about every 1/2" or so fill in between them, again one short run at one end, then one at the other and so on.

It's highly likely that you'll be grinding the weld flush anyway and it is possible to do the "spotting all the way" thin-metal technique fairly neatly so that it isn't too difficult to grind smooth.

 

[Sinister]

In agreement on the tack welding of body panels. Also your better off with butt welded panels, less likely to trap moisture and rust. Here's some welding I did on my truck. Sorry, no after the grinding pics.

 

[Chickenjohn]

The trouble with a continuous weld is that even if you manage not to burn through, the heat build-up in the joint and surrounding metal will cause severe distortion in such thin sheet and it'll look a right mess that no amount of grinding or sanding will sort out.

A good technique is to tack at intervals, one at one end, then the other, then the next at the first end, etc. Then do some more tacks between, still spreading the heat from one side to the other. Then when the tacks are about every 1/2" or so fill in between them, again one short run at one end, then one at the other and so on.

It's highly likely that you'll be grinding the weld flush anyway and it is possible to do the "spotting all the way" thin-metal technique fairly neatly so that it isn't too difficult to grind smooth.

I agree with this post 100%. That is exactly what I do when welding thin car panels. It is the only way to do it with Mig welding technique.