Mixing ballscrew types?

I started to convert my old 14 x 40 lathe to cnc. I have two
surplus (new) ballscrews. The one I have installed on the Y axis is
a 17mm Dia, (5mm / rev) thread, the one I would like to use for the
X axis is a 2.5in Dia, (.25 in /rev) thread. Is there any problem
using a inch and metric screw in the same machine using EMC? Will a
(1070 Oz in) stepper be large enough to direct drive my Y axis? How
about a (1200 Oz in) for the X axis?

Thanks
Brian