Thanks for all the help 80x40 it is then and I'll plan for using belts.

As far as the ballscrews go, would a 20mm 5mm lead not offer better accuracy, I'm not intending to do large volume runs of stuff so speed isn't that important (as long as it doesn't case any material problems) but precision for engraving is.

And last two questions, is there a good online resource for explaining the basic maths and mechanics for working this stuff out properly so I can stop vaguely throwing combinations of parts around in the hope that someone will work it out for me? :)

Is there a good all-in-one type book (real dead tree type) that covers all the basic aspects of cnc preferably with emc2 examples?

Ta very much!