Jeff,
Believe it or not i have this crazy idea of putting the lead screw inside the y-axis supporting tube. I was thinking that an ACME screw would be more vulnerable to contamination from cutting debris etc. than a ball screw, so enclosing it would be nice.
Using dumpster cnc's cut down flange:
http://www.dumpstercnc.com/images/fl...98_cutdown.jpg
This should fit inside the tube with at least 1/8" of clearance on each side, im not sure if this is cutting it to close. My one worry with the design is the distance the nut will be from the connecting y plane, the y bearings offset it 1" plus at least .5" to the nut inside the support. Im not sure if this connection will be to prone to flex under stress even with a .5" thick flange.
I am with my family for thanks giving until this saturday, when i am back i will be able to draw up a model of what i am talking about. This is still a very open part of the design however so suggestions are welcome and appreciated as always.
Thanks guys and happy holidays,
~Tyler