Is there a reason why the Greg Wades extruder uses 9 & 47 tooth herringbone gears? Is this ratio the best or is it just what happened to be used? Thinking about replacing mine with a pair of GT2 pulleys, but those pitches aren't standard. I could make them myself out of aluminum if that gearing is the best, but if 10 & 50 would work that would make things easier.

Also plan to make my own hobbed bolt out of 8mm drill rod and use snap rings to keep it spaced between bearings. It will give me a better fit in the bearings as well as the pulleys.

Thanks.