After cutting the key ways, it turne...

After cutting the key ways, it turned out that the shaft (bought new) was actually spaghetti. Visibly plus or minus 1mm at several points along it's 1300mm length. I set it up in needle roller bearings and V-blocks, then measured and massaged it to nearly straight. Biggest variation is now 0.1mm (around 0.004".), hopefully this will be sufficient.