Those were made in an era where manuals were not generally printed. If you knew what it was, you likely knew how to run it. Aside from that, lots of the magazines of the era carried how to info (popular mechanics, model engineer)
Check at Busy Bee Tools for a book called Screwcutting In the Lathe, by Martin Cleeve. It is part of a series of books called the Workshop Practice Series, and gives the basics for calculating geartrains , as well as some charts appropriate to the various standard leadscrews.
As you have found out, you own an orphan. No biggie, most machine tools are orphans in this day and age, esp once they reach prices the unwashed masses can afford.
You will want to know a couple things. The pitch (tooth per inch) of the leadscrew, the tooth counts of the gears you have (as well as the hole and keyway dimensions, the width of the gear and the keyway in the hole) Knowing the Diametrical pitch of the gears helps, as well when looking. If you have some basic measuring equipment, you can measure the diameter, count teeth, and calculate that.
Like as not the teeth are 20 or so DP, 14.5 degrees pressure angle, usually seen written as 20DP 14.5PA.
The simple way to explain the calculation, is to see that if the gearing between the headstock and the tailstock is at a 1 to 1 ratio, the thread cut will be the same as the leadscrew pitch. Everything else works out from there.
Cheers
Trevor Jones
