When I was at home my father had made a couple of shop seats out of tractor seats. The seat was welded to a pipe that telescoped within another pipe. Adjustment was a bolt or rod that was placed in holes that had been drilled into the upper pipe with a washer under the rod. This allowed the seat to swivel as well as be adjustable for height. His didn't have rollers, just the bottom pipe welded to an old disc blade for a base.