Thanks for the links; so it can be made to work - that's one very industrial looking machine! If I was making a machine for cutting metal I'd be tempted to go that way, albeit with the Z slideway arrangement done slightly diffeently. I won't be doing it myself on the thing I'm designing at the mo. since having a conventional dangly Z-axis is actually of particular use to me when carving out large waveguides, since you can get the spindle down inside the workpiece to some extent.