So I was poking around THK's site, and I see this:
http://www.thk.com/technical/download/f.html#3
It looks to be a precision ball bearing "drawer slide" with max clearance of .1 mm (.004")
They are billed as "low cost" as compared to the linear rail stuff.
Sounds like it would be just the thing for a CNC router... Is there a reason I've never seen this in all the pictures of home build CNC machines?
Thanks!
-Jeff