Originally Posted by labman
I doubt the dryer circuit has heavy enough wire to support a welder that draws 50 amps. Usually they are wired up with #10, limited to 30 amps. You might best start at the panel and run a 4 wire, black, red, white, and bare or green cable able to support 50 amps. The 50 amps is peak, not continuos? If the welder doesn't use a neutral, you would only need the 2 hots and the ground.
In the past, Dryers, stoves, maybe other neutral using 240 volt appliances used the same wire for neutral and ground. Newer ones use a 4 wire cable now.
Post back with whether the 50 amps is continuos or peak, and if the welder has any 120 volt components that need a neutral. Then see what tkrussell has to say.