I need to know the exact gearing ratio for my mill in backgear. This is for a gear hobbing project I hope to finish within the next X years (X has been less than one for a couple years now)

Anyway, I have an encoder on my drive spindle that does 4000 counts per turn. I ran the machine in backgear exactly 100 revolutions and got

2,451,765 pulses. I didn't use an indicator for the begin or end stop point (mark at end of 4" fly cutter lined up) so the true total could be +/- 250 pulsesThis gives a gear ratio of 6.1294. I need a really good guess on the number of teeth in the drive and driven gear. For example, if the drive gear has 10 teeth and the driven gear has 60 teeth, the ratio would be exactly 6.00. There's a zillion possibles, I'm looking for one that give a number within a couple tenths(.0002) of this ratio.

If I have too, I'll tear the machine down. But, I'm hoping there's a math genious out there. If needed, I could put a counter on the spindle and do

1000 turns.Karl