You say that you went to plug in your 220V welder and the plug did not match the receptacle. Is it a 220V receptacle? Have you used it as a 240V receptacle in the past? I really don't want to sound condescending, but your post was pretty vague. I have a Miller welder that will do 120 or 240. The main plug is for 120V, but it came with a 240V adapter. It works great on 240V. I have welded 1/8" plate with it on 120V. If it is a 240V receptacle and the tangs don't match, you can always buy the correct plug end and wire it to the end of the cord. Or, like @Professor Fate said, maybe you could find an adapting pigtail.