tool changing

It's still a manual tool change, but because you can preset the length and load it into the spindle in a consistent way you can have multiple changes of tool in the one program.
My one is specific to my brand of mill but you can get the idea.
sherline.com/product/3079-end-mill-holders/

verticalperformance wrote: Simplest thing to do with collet type holders that may get loaded to different heights each time is to break the gcode up into multiple files, one per tool..

It is sometimes easier to change the part than the tool, and this approach makes that easier too. (run the sections one by on several parts each)