Has Jon says the critical speed is a guide and the reality is that you'll possible double that and still get away with it.?. . My 1500mm x 20mm screws do.!

Regards me using 1:2 mostly well that's not exactly correct. Since the last time I changed back to 1:1 it's been left that way and when I do change back it's going to be 1:1.5 because I don't the speed. I don't really need the torque or the resolution either if I'm being honest but that little overhead helps when I do need higher feeds.