This method has been discussed on here before. Since I never have any new ideas, this is how I did it.
First take a 5/8" x 3" bolt and cut off the head.
Jam two nuts on threaded end.
Chuck bolt in drill press.
Grind taper with angle grinder while running drill press.
Finished Bevel on nut.
Install beveled nut on a 5/8 " bolt.
Use Locktite to keep nut tight against the head of bolt.