When I print a shaft parallel to the print bed (sometimes that is just the best overall orientation), the shaft is not very round. This particular instance involves a 6 mm diameter, 10 mm long shaft to hold a bearing. I need at least ten of these, so using a small file and finger held sandpaper for cleanup is not very attractive to me. I made a tool bit that I insert into a portable drill and use that to buff the axle into shape.
Print with the shaft upright, no supports, 100% fill.
If your axle is 6 mm in diameter and 10 mm long, this will work. Otherwise, I included the 123D design file which you can modify to suit the diameter and depth needed.