Metric Threadcutting gears for antique South Bend lathe

[Toolmaker51]

I don't see these so much a dodge, but extending capability using almost simple mechanics. It's juggling 'as built' components to reach or approximate other ratios. No reason to avoid incorporating any potential new ability.

Despite metric/ imperial established so long ago, VERY FEW lathes encompass the full range of both. Not practical design or marketing, with thread pitches and feed rates coupled to diameter - a 6" lathe would rarely be called to generate 2 pitch, nor a 24" doing 32 tpi. The large machine has what appear fine pitches resulting from accommodating feed rates. The reverse for small lathe isn't so.
For any involved with equipment repair, producing any pitch isn't required lets say 15 or 17, just the real pitches like 8-10-12 etc; of course extends same way into metric.