Thread rolling was a normal production process where I worrked at Joseph Lucas back in the '60s. There were specialised machines that rolled the blanks between 2 flat die plates. These were capable of very high production rates of high quality threads.

Rolled threads are stronger and more fatique resistant than cut. This can be the difference between life and death. There have been cases of wings failing on aircraft due to cut threads. Specific cases were Tiger Moth and Stampe biplanes. See:
https://www.atsb.gov.au/sites/default/files/media/5750718/AO-2013-226%20final.pdf

and

https://assets.publishing.service.gov.uk/media/5422f6c240f0b613420005a3/Stampe_SV4C_G__G-ATKC__02-88.pdf

This second report also highlights how making the tie rod of consant diameter raather than the original waisted design increased loding on the threaded ends as the thicker, stiffer part did not share the load as well.
Details details. Never assume you know why someone designed something a certain way unless you have a detailed description from the original designer.

I hve a old thread rolling die on my bench. It makes a nice bench block

Robert

Edited By Robert Atkinson 2 on 01/03/2023 11:58:24

Edited By Robert Atkinson 2 on 01/03/2023 12:05:38