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.