welder/welding

You guys hit them all, I wanted to add a few more:

Make sure your MIG tip matches the wire and is new (enough) and tight. Airflow around the piece can ruin the weld. Angle, speed, practice etc. I find setting can really make a difference. I have a Millermatic 110 and it does everything I could want with two different wires. I use CO2/AR mix and flow rate right around 20 for indoor. I tweak all of these depending on what I am doing which brings me to....

My suggestion to add is you need to plan and worry about heat. Where is the heat penetration, how does it build and where will it go? Look at what you are doing and figure out the heat path. If you don't, you will get burn-throughs, warping, bad welds and pretty much make yourself feel like you don't have a clue how to weld.

For example: Welding a 2.5" muffler pipe that is slip fit has lots of heat-sinking capability (big metal can), but if you try and weld a butt-connected quarter-panel the same way, you will warp and burn through it quickly. Each take different techniques and you need to identify which you need by thinking.

RGAZ