"@DoricYeah, well if you make it back through the weeds I have a question that's right up your street from the sounds of it.  I need to know if there's an easy way to tell what specification of screw a CNC machine uses, short of dismantling the thing and sending off the screw.  It's easy enough to do but I don't want to screw-up the precision until I've used it to cut parts needed to extend it."

Micrometers and thread pitch gage.  Unless it's a ball screw, then entirely different methods are called for, and equipment I don't have.  You don't say what kind of screw, as in use in the machine, so I have to assume lead screw and saying CNC would mean ball screw.  Also if it's a lead screw, and not a ball screw, you have to see the end to make sure if it's single or double lead, meaning a thread pitch gage would say it's for an example, 10 TPI and in reality it's 5 TPI double lead.  A single starting point on the end, single lead, two starting points, double lead.  Also could be right hand thread or left hand.  Chinese, my guess is it's probably in inches, not metric, if not a ball screw, Acme thread form, 7.5 degrees on either side of the thread.  If made for the UK market specifically, maybe something similar to an Acme, or could be 55 degree whitworth.  Standard SAE thread form in the US is 60 degree thread.  If you can find a copy of Machinery's handbook, specifications for every thread you can think of would be in it, but it's a US publication and quite expensive.  Which printing you might find makes no difference, thread forms do not change with time, new ones are added, the old stay the same.  If you don't have inch measuring instruments, the conversion is simple, 1 inch equals 25.4 mm and that's not approximate, it's exact. 

If you get lucky, and it's an Acme thread, that's available like threaded rod is, not cheap, until you try doing it yourself, then it's really cheap if there's any length to it.  Just buy it long enough all you have to do is machine the ends.  Threading long rod isn't something I really enjoy doing, and it usually requires a follow rest, making it an even worse PITA.

Doric

The "I" in Doric is Silent.