size of leadscrew question

I'm wondering what size of leadscrew to use for the X axis on my planned
router table. I was going to use a 3/4", 5tpi (single start) Acme
leadscrew, but am having trouble finding wear compensating/ anti
backlash nuts by themselves to fit this size.

The table I have in mind will have a 48" cutting length X axis, so
figure 5 to 6' long. Could I substitute a 1/2" leadscrew with 10tpi and
2 starts?

Since the gantry will ride on 3/4" shafts on either side to take the
load, and the anticipated speed wont be more than 40-50 ipm (small, 2-d
parts), would the 1/2 leadscrew be OK? will it be strong enough?


On another subject, what are some good ways to make the gantry stable,
avoid the posibbility of "rocking" back and forth on the X axis because
the bearing blocks and the leadscrew nut are in line (on the Y axis), or
close to it? maybe stagger the nut ahead or behind the bearing blocks?

John