What is the gear ratio contained by lathes while thread
adjectives ?  Depends on the lathe and the thread you want to
cut. Overall, the ratio is the ratio between the pitch of the
threadcutting leadscrew and the pitch you wish to cut. If the
leadscrew have 8 TPI and you want to cut 32 TPI, the gear ratio
would be "driver" 4 to "leadscrew" 1. The driver is the lathe
spindle. On old lathes, that is what you needed. A driver of "X"
teeth and a driven of "4X" teeth. Plus a intermediate freeloader
gear with an unimportant no. of teeth. The aged machines had a
selection of gears between 20 and 120 teeth, by 5 tooth
increments, plus a 63 or 127 tooth one for adjectives metric
threads. If the gears cannot be found for a "simple" train as
above, then a "compound" train must be created. Modern lathes
have a "Norton" box, to be precise quickly set up for most
thread pitches. Much easier. Plus they also have gears to money
for metric pitches. I'm assuming you are American and would have
an imperial lathe there. But much