I have read and reread the discussion on how to address these components, with no clear picture emerging of the approach the author intended.
So my approach was as follows – we will discover if it’s a good one. Clearly, perhaps the biggest issue is that the top and bottom faces of the columns are true to one another and properly perpendicular to the crosshead slideways.
So, looking at the castings I concluded that the most solid foundation to support during most of the machining IS the slideway facings – so we will start there, and then turn it over bolt it down and try to do the rest.
Sadly, the Adcock & Shipley cum Bridgeport Mill I created does not have a very big table or much movement in the Y direction (6 inches), so one can’t do them as a pair.
So as this picture shows, I supported the two ends of the casting and fiddled till the face of the slideways was horizontal in two planes – then clamped it down and set to with the flycutter…
Here’s a mobile-phone movie… sorry about Bob Harris in the backgound!