Don't be afraid of trying nickel silver. Just pick the right alloy and don't try to go too deep. OK, so which alloy? Try what's called leaded nickel silver (C792) as it machines like 360 brass. You could also try the more conventional alloys like C752 but you just need to be careful.
4D operating at once can be used to make diagonal teardrop patterns on a cylinder. The teardrop shape being generated by changes in Z (depth) while simultaneously moving X and Y and rotating. It's a very pretty effect.