Hi I've been lurking on the site for quite a while but have been stirred into action by the excellent introduction to 3D printing by ParCan and craynerd's build log for his Prusa Mendel. I have had a Prusa Mendel running for about a year and have recently started building two new Repraps. The first is the Prusa Air, which is similar to the Prusa Mendel but uses laser cut 6mm acrylic for the main structure. The second is the Huxley, which is a smaller version of the Prusa Mendel using 6mm rod instead of 8mm. I've attached a few photos to show where I've got to.
The first attachment shows the smaller Huxley, the second a general view of the Prusa Air. The final attachment shows the Z axis nut on the Prusa Air. I used steel hex drilled out to take a bronze rod, held with loctite which was then tapped M8. There are a pair of such nuts held in the black printed housing held apart by a spring to give an anti-backlash Z nut. The combination of Stainless steel screwed rod and the Bronze of the nut should run better than simply using a stainless steel nut.
Chris