Nice video on making a rotary for the K40 and then using it with K40 Whisperer.
Brillant! My only concern would be cutting out the bottom of the case; I had bloody hell trying to square up things when I first got my laser and now I live in mortal fear of doing any case mods. Still,a very impressive project.
You could make a metal (angle iron) frame that goes under the K40, as you have to lift it anyway, and bolt it to the bottom, then cut out the sheet metal.
Does the rotary scale factor need to be calculated/changed for every different diameter of objects you are engraving?