Threading of CNC!!

I would like to conver a 9x 12 lathe to CNC!!
I am thinking to substitute the powerfeed leadscrew by ballscrew
driven by stepper motor!! But if I would like to cut L/H or R/H
thread, how can I do that without gears driven by spindle??
Variable speed control lathe????
Can it be controlled so accurately to cut thread or I still need the
gears????

Could someone give me some principles???

Many Thanks!!
Tom