By "straighten up what's left" Hotrod is saying to "chase" the threads on the "bolt"/steering shaft with a thread die, carefully. Make sure the die starts on the same threads that are already there!!!! BEFORE THAT, use a file to chamfer the end of the "bolt"/shaft to get rid of the goofed up threads/bulge so that the die will start. Sometimes you can use a thin hack saw blade to freshen up those first goofed up threads. After you have cleaned up the threads/shaft, as he said, Get a NEW nut and run it up and down slowly to see if it is going to thread on easily without using a wrench, especially don't use a socket wrench to test because you can't see what's happening, then install wheel. You only need a three or four thread engagement of the new nut outside the wheel hub. DO NOT USE THAT OLD NUT AGAIN ON THE SHAFT. KEEP IT AT LEAST 10 FEET AWAY AT ALL TIMES.
