metric threading chart

I made a threading chart for my 10" SB that lacked the plate by writing a spreadsheet which included the tumbler and banjo gear ratios in the formulas. As I didn't know the gearbox innards I reverse engineered the pitches from a photo of the gearbox plate.

I found that a 120/127 metric gear set would add more fine threads for the optical stuff I was making than the standard 100/127 set.

-jsw