Re: Welding a rollcage
Lay a couple of pieces of 3/16 next to each other - for a butt weld about 1" long. (1/8" is typical cage material, 3/16 is typical frame material.)
Do the best job you can welding it.
Then look at the back - did it penetrate?
Is the back melted together? Or is there just dribbles spots?
Did the weld go all the way through?
Or just stay on the top surface? That's penetration.
To be strong the weld has to be just as thick through as the base material or more -- and properly joined to the base material all the way through - else the weld's the weak part.
Put it in a vise - bend it toward the top till it breaks. Look at it close. How much through was melted - what broke - the weld or where it was attached? Or did it even break? You should be able to bend it like crazy.
Do another one just like it - this time cut across the weld with a chop saw or grinder. Look close - how deep did it penetrate? Dip the end in pool acid or battery acid a few minutes, wash it off. Now look at the cut end - you can see how the metal structure was affected by the weld and how far into the base material was mingled.
Unfortunately on frame fixes and roll bars you can't get to the back to run another bead or even see it.
The little 110 volt MIGs are great for sheet metal work - actually better than the big ones since there's better low end control - but for heavier you need more heat - especially in critical areas like safety equipment.
Not fun to be hurt by your own safety equipment.
If you are doing it as a business, think of what just one lawsuit would do to you.