SteveF wrote:

this is more of a "how to use my lathe" machining question.

I have absolutely no idea if this is going to work, but it is just an
idea to save on 2nd, 3rd, etc, realignments (which probably saves
nothing if you are making it for your own lathe).

1) Make first bit of threaded screw.
2) make threaded tube to match screw, tube extends through head stock,
3) make "lock nut" (or 2?)
4) mount threaded tube into jaws,
5) load lock nut onto thread part of screw
6) load threaded bit of screw into tube
7) lock threaded screw into threaded tube
8) align in jaws and tail stock
9) realign tool.
10) cut next section
11) unlock lock nut(s)
12) screw threaded rod through threaded tube and relock[1]
13) got to 10.

Theorectically you could make it as long as you like, but you need
steadies on the long bit,

[1] each turn just advances the rod the size of the pitch.