[clutchslip]

Just to show it is possible if you have to convert fixed cones into adjustable ones.
Using a stout boring bar with a carbide tip, 500 rpm, don't mess about and put a 0.3mm (0.012") deep cut x 3mm deep and repeat until the counterbore clears the locknut, no coolant used, job done.
Alternatively if you know someone with an EDM machine use that!