This is a good design for use at the bench which will allow the welder greater comfort for repetitive or small work. When not in use, it will swing under the bench. The seat and smaller pipe are welded into a single unit, which allows it to move up or down inside of the pipe sleeve. Both the sleeve and smaller pipe have holes drilled at 1" increments through them to allow the pin to be used for the vertical adjustment. 

     Alternatively, a threaded rod and sleeve could be used, allowing the seat to be adjusted by spinning it. The seat swings back and forth by means of, again, a smaller pipe inside of a larger pipe. The smaller pipe in this case has a larger washer or nut welded on the top end to keep it in place. The two clips have holes in them that will accept the smaller pipe into the pipe sleeve. The larger pipe sleeve is welded onto both clips. The clips in turn are welded to the bench leg. Remember to check the rough height before installing onto the bench.