if the axle is too thick, get a flat bastard file and open up the slot a little. If there is a "thicker side" (meaning top or bottom) try to remove more material from there. I think you are trying to say that the axle fit before you p-coat, and if thats the case, you will have very little work to do. 60's lugs should be plenty beefy enough to remove a little material and still be totally strong enough. I had to do this on my old Raleight and never had a problem.

use a dremel if you're feeling lazy.