Here is a gearing program that runs on Linux (wine) or Windows that can be used to deduce other gear combinations. Note that the 127/100 compound gear is not used. This magical gear is what makes the lathe exactly metric. The lathe, like most, has an 8 TPI imperial lead screw. The 127/100 effectively allows the imperial lead screw to have a 100 metric divisions. This is because 1 inch is equal to 25.4 mm. Therefore, 254 / 2 is 127 and 127 is prime. Which means its not possible to get a smaller gear that will divide exactly.

lead screw | inches | mm | equivalent teeth on theoretical compound gear | |

8 | 1 | 25.4 | 1016 | |

4 | 1/2 | 12.7 | 508 |

As you can see the table above lists theoretical gears with impractical numbers of teeth. This is made practical by another compound gear the 72 / 18 which is a ratio of a 1 / 4. 12.7mm / 508 is 0.25 which provides the metric basis to work with. The other gears provide ratios of on this.

This is a link to an online gear calculator.