i don't think i ever weld anything with my miller mig i worry about being to cool. i usually only use it for sheetmetal and body panels and if you hang around in one spot too long it will burn thru. if it's thick enough at all i will turn on the big hobart dc arc welder. i don't think i even tilt my arc welding electrode 45 deg let alone my mig gun. you will know if you are getting good penetration or not and adjust something accordingly, it's never a problem with the stuff i weld. i welded a piece of cast iron today and when i turned it over i couldn't even tell where the crack had been, which is very unusual for me and cast! but the last inch the heat got to it and it wanted to blow thru. this was not with my mig though, i was using arc with cast rod. if you try flux core you will prob hate it, i did. but i'm no welding expert and don't pretend to be. hr
