I have been making pillars from nickel silver. The two pillars that fasten to the foot have cross drilled holes that are off center. This helps balance the Front End Ring with the heavier Rear End Plate.
I buy 18% nickel alloy from suppliers that cater to knifemakers. I don’t know for certain that it could be certified as c752. On Line Metals now offers 12% nickel alloy c792 in diameters as small as 3/16 inch. This would also be a good choice. For the highly machineable c792, I would make the tap holes with #47 drill.
I make the frame screws from standard pan head screws, modified by turning the heads to a smaller diameter. Turning also improves the concentricity of head to thread. The turning fixture is a rod that is drilled and tapped at one end.