David,
I metal spin ends for fuel tanks from emersion tank copper, I made my former from a piece 1/2 " mild steel by machining a half ball on the end and polishing the end to near mirror finish, If you dont get a good finish it will show on your work as marks,
I use the tool clamp bolts on my tool post to guide the former, I use tallow as my lubricant and can I ask what your lathe is as you need to have a strong tailstock to stop the work from leaving the machine. When I make my parts I have to heat treat the copper as it hardens very quickly, you may find brass will do the same.
There is a good booklet on the subject produced by the publishers of the Exhibition hall at Fosse Way, currently I cant remember it but will hunt it out if you need it.
Martin P
Edited By martin perman on 22/02/2019 18:10:23