i bought a used welder that requires a 50 amp circuit.
what size wire do you recommend i use with a 50 amp double breaker?
For a 50A load, you need #6 copper wire, if it's a distance of about 20 feet. If it's longer than that, you need to go up to a #4 copper.
If use 6ga wire at the full load of 50A, you would be good to about 130ft before voltage drop became much of an issue.