As a diesel fitter in the shipyard, we always used a thread guage to determing the threads per inch. Of course you could use your eye and measuring device to count them. In a pinch I've used a small 3 sided file to clean up threads. You can use something like prussion blue on the nut threads to see where its binding on the spindle threads and then work on that area.

I would rather be late 10 minutes in this life than 10 minutes early for the next

The reason my lady and I have been together so long is because of the kids. Neither one of us wanted sole custody