My lathe is similar size to a Student, I used a 400 oz/in on the X axis at 2:1, plenty of power. I used a 1200 oz/in on the Z axis at 1:1, it has enough power but my voltage is a bit low I think at 48 volts. I get a rapid of about 55 in per min at that. I did the 2:1 on the X axis and 1:1 on the Z so that with 10X microstepping and .200" ballscrews I would have .0001" resolution on both axis, the X needing twice the normal because of the diameter change. Just remember, the Z axis needs at least 3 times the power that the X does, much more weight to accelerate there.