Slightly off topic - DC motor control for 9X20 lathe

I recently purchased a used ENCO 9X20 lathe and plan to change the
motor to variable speed drive and X-Z axis to CNC with steppers.

My biggest gripe with this lathe is the sleezy drive train and lack of
slow speeds. I really want variable speed if I can figure out a simple
and inexpensive way to do it.

I am wondering if I can use a variac with a bridge rectifier to produce
variable dc voltage to run a DC motor? Is there a better and affordable
way???

Comments and insight welcome!

Jack