Glenn, the axle threads are cut, it would be totally impractical to roll the threads for a number of reasons.
On my one piece axles there is NO threaded portion of the axle residing inside of the swingarm plates, in other words
there is no weak point in the axles length, the only way my axle could break at the thread would be by overtightening
which would be near impossible. As a comparison I measured the surface area of a standard axle at the thread root diameter which by the way is less than .500" compared this to the surface area of my full 9/16" diameter axle, the surface area of my axle is 33% more.
I would say that most standard Norton axles break at the end of the thread is not because of the small diameter but
a combination of poor design and or poor fitment by owners.