Hi Dan,

Quite a big machine you have planned there! Any thoughts on what materials and projects you will cut with it - that will help people with suggestions.

How about the electrics side, stepper spec, drive voltage, spindle type (Dremel, router, spindle)? What about the drive systems on the other axes? Any ideas about jog rate?

How much Z travel are you thinking off, considering max work piece thickness plus some clearance to allow easy setup?

For further design ideas have an internet search for:
Joe's 4x4 hybrid
Mechmate
Ironman
Shopbot

Thanks . . .