Last year I got really lucky and found a nice table on Craigs List only a few miles from here. It's about 4' x 5' with a half inch thick mild steel top supported by heavy wall steel tube for a frame. It rolls on 6" steel casters with locks on two of the wheels. There's even a shelf underneath that's almost as big as the table. Before that I had to make do with a 2' x 3' wooden shelf with a piece of 1/8" aluminum for a top. Not much good for pounding, couldn't tack anything to it, and I melted places on it a couple of times. Still, it was better than nothing. If cost was no object, I'd build one at least 4' x 8' on a heavy steel frame, caster mounted, with a stainless steel top at least 3/4" thick. But that's probably off in the next life...