127T change gear for cutting metric threads on a Harrison L5 lathe

The 127T gear is necessary for cutting metric threads on the imperial Harrison L5 lathe. (12.7mm is precisely ½" so 127T gives an exact conversion). Other gears needed to cover almost the full range of metric thread pitches are 40T,50T, 60T and 63T. I remixed this from my previous Harrison gear code that uses customiser to allow you to dial up the number of teeth you want. I would not recommend running with plastic on plastic but I have run 3D printed gears against steel gears for a while no