andypugh wrote: If you are able to always set things up so that the centre of rotation is Z=0 it is possible to create a config that converts Y (in G-code) to A (on the machine). That means you can engrave XY patterns on any solid of revolution.
But, the point is that it will always be XY G-code unless you get a 4-axis CAM system.
For simple cylindrical work, you could create a system where the working radius is set in a GladeVCP or PyVCP control on the screen, and a simple scaling in HAL converts Y positions to A-angles.
For more complex solids of revolution you probably need to consider doing the "magic" in the kinematics.
Thanks. Ya, it sounds like I will be just changing configs when I need to switch from flat to round.