Yet another question in my bid to gain knowledge :).

Does anyone know the metric trapezoidal equivalent to various ACME leadscrews?

ACME leadscrews are sized as say 10tpi single start, so 10 rotations = 1 inch of travel. A 10tpi 2-start has 5 rotations = 1 inch of travel, in metric land the 10 tpi single start is equivalent to a 2.54mm pitch trapezoidal leadscrew I believe, but what is the equivalent to the 10tpi 2-start? 5.08mm 2-start?

This is almost frustrating, I started out thinking 'I want to do ZXY', but every time I look at any particular part it throws up more and more questions . Fortunately I love meeting challenges, and solving problems so this is still fascinating & fun :D.

Just to give some idea of what I'm thinking, my plan is something like this:
I want to build a basic router as a learning exercise, that I can then use to make the (first :D) proper router with. I am thinking of the proper router being something similar to the Joe's 2006 R-2, and to save money I want to build the basic one using parts that can be reused, i.e. x-axis leadscrews and bearings of the basic becoming the y-axis of the Joe's 2006.

If you think I'm completely mad let me know :D I already know I'm slightly mad ;).

Or if you've got any suggestions for different machines, parts, or anything really, please speak up :).

BTW the reason for the original question in this post was that alot of people in the states are using 10tpi 2-start, or 8tpi 2-start ACME rods with success in their Joe's 2006 routers, and I don't want to blow £30+VAT and delivery on the wrong material...