If the price is right, I'm thinking about making a small (6"x6"x6") DIY jewelry mill based on Pacific Bearings, Dolphin series of linear guides.

According to their white paper, their Dolphin series of linear guides have less than .0005" end-to-end yaw and pitch and typical ball bearings have .0035" end-to-end yaw and pitch.

Anybody have any experience with these?

http://www.pacific-bearing.com/about/