Re: Frame Building questions
I have no welding experience. I asked the very same question and many hours of research brought me this:
I've found that the cheapest useful method for bike frames will be MIG welding with flux-core wire or with gas shielding. I think even the cheapest MIG flux core welders will allow a gas hookup for when you rent Ar and CO2, so you could start on the cheap with flux-core.
Research gave me a very wide variety of opinions with a common denominator: "take a welding course and then you'll know for 90% what equipment you need". This answer was very frustrating.
Of course me being a cheapskate, I won't be taking a course. So I did even more research.
Worst to best is AC arc, DC arc, MIG flux core, MIG gas, TIG.
The price difference? basically add a 0 to the price for each step up between arc, mig, and tig. i.e. $30, 300, 3000+. I almost jumped the gun on a $50 AC welder, until I started doing more research and found that it is difficult not to burn through thin metal with AC stick.
In fact, all this research and needing to buy the welder, then spend a few days or weeks learning how to use it, has just caused me to look for a project that doesn't require so much welding.. something I could take to the local welder for $20 (like stretching a motorcycle swingarm.. etc). Suddenly building my own frame doesn't seem so attractive an option!
I don't always listen to Alice in Chains..... but when I do, SO DO THE NEIGHBORS