Common practice is to do a slight chamfer. I do mine on a belt sander, using
a rolling motion to impart a slight radius to the shaft end. Nuts spin right on.
I have no fear of cutting allthread anymore since I learned to chamfer the ends
on a belt sander (linisher to the Brits).

Grant Erwin

Richard J Kinch wrote:

How do you get a clean start to outside threads cut on a lathe? For
example, if you threaded the outside diameter of a rod, where the end of
the rod had been perpendicularly faced, a geometrically perfect thread
would end in a knife edge. Simply chamfering the corner doesn't really get
rid of it all. Ideally you would want the thread that just suddenly ramps
up out of the minor diameter, like is formed on the end of a common
commercial bolt.