Because it will have you a lot more control over the whole process and it is more forgiving in case you do anything wrong.
How to mig weld automotive sheet metal.
The main reason to use a smaller diameter wire is that it takes less heat for melting and hence the metal around the weld is not heated to a very great extent.
Short quick welds when welding sheet metal with a mig welder you do not want to try and run one long bead like when you re welding heavier metal.
While replacing body panels overheating and warping thin sheet metal is common.
Avoid warping the sheet metal.
Place the welding tip wire at the gap and tack weld several small spots spacing them evenly apart.
Ditch a 1 8 inch tungsten electrode for something much smaller like 1 16 inch tungsten.
Andy gives helpful insights and tips to mig weld thin sheet metal.
For mig welding sheet metal it is often recommended to use an electrode wire of the smallest diameter to prevent burn through and warping.
Then tack between the two previous tacks.
I keep blowing through my thin sheet.
The best two electrodes for welding auto body sheet metal is either ceriated tungsten or thoriated tungsten.
When welding a long bead on sheet metal you ll put excessive heat into the panel and run the risk of the puddle falling through the panel.