[HELP] 6" Fortis/Clausing lathe

[Seanlogie]

I'm new to this forum ,but I've been looking on here for a while now ,everyone seems very civil to each other and helpful ,which is great because I'm needing help with the Fortis/Clausing  lathe i have . I'm trying to understand the quick change gearbox for threading .

   





This one 
 http://www.lathes.co.uk/fortis/

It's a clone of this one 

http://vintagemachinery.org/pubs/182/4966.pdf




Thanks for Looking 
Sean