servo sizing

thinking about using geckos servo drives to put on
a small lathe (old hc chucker) or maybe a mill later on
from what i have read here servos have a different power curve
than steppers
what size motors would be used on small lathes and bridgeport
size mills
also sense you can use regular brush dc motors
and these are marked with hp or volts and amps
is there a conversion from hp/watts to in/oz

hopefully gecko will make a nice ref on servos like they did on steppers
mike