Dave brings up a great point that I have never thought about because I have never used a 120V welder. I'll bet there are JILLIONS of these machines plugged into 15 or 20 Amp circuits everywhere.

When was the last time you saw a 30Amp 120 V outlet? They are not common and if your garage has one that was put there by the builder, you probably have a one in 10,000 house and it is only there because you or the builder of the house specified it.

Good luck,