motor gearing and leadscrew torque

can any body explain how to calculate the output torque on the
following setup:-
110 oz/in stepper motor
4mm lead leadscrew
what would the effect be of gearing up the leadscrew maybe 4 or 8
times to get more traverse speed as the motors only revolve at maybe
2.5 r.p.m max so traverse speeds would be slow without gearing.would
the torque still suffice to drive my home made engraver/router?.
any info would be gratefully received.

thanx in advance
mark