So am I right in thinking that where the screw ends and the machining begins is where it butts up against the bearing inside the housing?

Or put simpler if I ordered 1200mm of screwthread (plus the machining) with the bk attached at both ends I would have 1200mm of screw between the faces of the bk blocks?

I have just redesigned how I am mounting these as to start with I had fixed plates to hold the FK version bearings but was a little concerened that if I order this screw and find its even 3mm oversize length on the machining it wont fit so by going back to the bk style I have a bit more flexibility.