Today I’m jonsing for my mig welder that was lost during a move. Remember the microwave oven foundry? If you’ve got a few old ovens around, you can gut em and build an arc welder. The transformers generate the voltage, and an SCR circuit makes the arc adjustable. Of course if arc isn’t your style, you can build your own TIG welder. Since you can score an arc for $150-300, but a TIG costs more – I’d go TIG.