I get almost perfect results every time irrelevent of the type of the repair by spotting with the MIG and quenching the weld area frequently so as to limit the heat soak along the panel.
The MIG heat soak is only for an instant for each spot when quenched using a damp/wet rag.
The MIG requires only one hand, the second hand is usually needed to hold something important. The mig spot weld is instantanous.
The negative side is that if ham fisted the operator can easily blow holes in the thin sheet metal.

Both TIG and oxy apply heaps of heat to the panel prior start of welding, which usually needs to be seam welded, which adds even more heat over a much longer period of time. Both tig and oxy always require two hands.

Maybe at your next lesson at the panel beating course you can ask the teacher exactly what the oxy and TIG heat does to the crystaline structure of motor vehicle sheet metal, especially in the zone immediately adjacent to the filler material and the parent material. Ask him also what are the ramifications of using oxy or TIG (ie heating in excess of 300 degrees Celcius) on the laminated high tensile steels new car bodyshells are manufactured from. If he is good he will be able to distinguish between the laminated high tensile steels used in the stressed chassis components such as chassis rails, as compared to the outer skins of the bodyshell.

The true test is to research exactly what processes the motor vehicle body manufacturers have used for the past 25 or so years: if they can't spot weld they usually MIG. I can't recall ever seeing a motor vehicle manufacturer using TIG or oxy on new body shells.

Thanks to all.

I will get a MIG and just do a lot of practice.

Cheers

Matt

I agree with mig being the weapon of choice for sheetmetal. Unless you are a true craftsman trained years ago(if you were, you would us an oxy)mig is the easiest...the only disadvantage is that the weld is so much harder than the metal being welded, this can cause cracks if the metal needs to be worked after welding. It is a must as PeterM says, to quench the weld and do it in small spots...especially when welding sheet under 2mm in thickness. Oxy is the best for thin sheet but there are not many people who can control the torch properly and quench at the correct rate and location around the weld(hence needing to be a true craftsman)

I just did the rust on my escort, C pillar, heater bubble, sil, boot/rear windscreen with oxy/acyt and had no issues, very minimal panal warp, but then i just heated it up and lightly tapped it out and came back fine, and i have had to use almost no filler.