Might be a bit OCD on needing that thin gap, perhaps.. think about a 2 nut instead?
Of course, the top cap is thicker ,
it has to be internally threaded, lock nut externally threaded and internally tapered,
to compress the collet, as it is tightened down..
http://chrisking.com/tech >>
http://chrisking.com/files/pdfs/GripNut.pdf