This was an incredibly difficult project to fixture. The goal was to shorten the king pin bosses while maintaining perpendicularly to the pin centerline. By holding the king pin a 3-jaw lathe chuck clamped to the table the pin was perpendicular to the mill table. The king pin boss fit tightly and was clamped down with a bridge clamp on a bolt tightened in the set screw hole. The axle was supported with a screw jack and captured to prevent rotation. Once held properly, all that was required was simple CNC program to circumscribe the king pin. It worked fabulously!