^ +10. Bench Vise is essential for this. Turn the wheel horizontal and clamp the lower (non working) outer locknut in the jaws. Then, work from the top. You'll have access to both slotted cones (above and below), and to the top locknut. Adjust the cones to a loose position with just a "smidgen" of play, and then tighten down the top locknut while holding the top cone in place relative to the vise. The tightening will take out the play.

Trial and error until it's perfectly done. Good luck. PG