People get put off MIG due to the cost of mixed gas. My welds are not for public view so I just use CO2 which I get from a bar which we own - cylinder lasts us years - if you have a friendly pub landlord he might let u have a cylinder - they tend to accumulate 'lost' ones
Welding car bodies you will be grinding down to a flat finish so any spatter from using CO2 won't matter.
I make up chutes & hoppers from sheet which is probably
1/1.5mm with MIG and I've had no training at all.
MIG is much easier than stick as you don't have the problem of arc striking and 12" of rod to keep control of.
With MIG you are able to concentrate more on the end result and how your technique is affecting it.
As mentioned previously hole filling can be done by stop/start welding as you can spot in small adjoining blobs without needing slag removal that form the backing for weaving/beading over.
Get an auto dimming helmet - as useful as the welder itself DJW have for about £90
It is possible. It is difficult. It is also not recommended by the car manufacturers because they have switched to HSLA (high strength low alloy) steel instead of the plain low carbon steel used in the past. HSLA weld strength is a very sensitive function of the size of the HAZ (heat affected zone). The manufacturers insist that you only use MIG or spot welding to minimize the HAZ during a repair in a modern car. That's because the sheetmetal bears structural loads in modern frameless construction.
Even for an older car which has a full frame, and whose sheetmetal is not structural, you want to minimize the HAZ to minimize *warping* of the panel. So again MIG would be preferred over arc or gas torch welding, and stitch welding would be preferred over full seam welding to further help reduce warping.
If the holes you want to fill are due to *rust*, then further issues arise. First, you need to grind back to good metal before attempting the repair. Second you'll probably want to fit a filler panel rather than just trying to weld the hole closed. In modern cars, where the area being repaired is structural, you need to take a very close look at the whole area before attempting the repair. Best practice may be to replace rather than repair if the weakening due to rust is extensive, or if the area to be repaired is at a high stress point.
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