Would like to see your setup, any pictures or video?, do things move freely with no wobble in the drive shaft and a smooth action with constant load for stepper? My initial testing showed that it has potential but requires good straight parallel drive shaft and side smoothrods. Using a 20mm pitch with 8mm smoothrod could be too much angle to keep things accurate, try thicker rod and less pitch, am using 15mm pitch and 10mm smoothrods here. The shaft needs bearing on each end to help support it, need to add an extra bearing today, this is current test jig. http://www.youtube.com/watch?v=uzSgV8Ecu7Ahttp://www.youtube.com/watch?v... .