Here's my helical focuser write up:
DIY Helical Focuser
Hope it helps
Sky-Watcher Explorer 150PL, Celestron C102 Wide View
HEQ5, EQ3-2 Dual-Axis Motors, Motorised Focuser, Homebrew Autoguider
Paradigm 12mm, Sky-Watcher 10mm & 25mm, Celestron Omni Plossl 40mm
Sky-Watcher Deluxe Barlow
Canon 350D (IR Filter Removed), Meade DSI, Microsoft HD lifecam Mod
Bresser 10X50s