With no ATC on the Probotix machines I have and used while teaching I dreaded complex jobs (just a little) that required tool but changes. Whenever a job needed chamfers on bolts hole I used this trick so I didn't have to change to a V bit. My blog: Bolt Holes with an End Mill.
I've posted downloadable .CRV and .CRV3D files used to make the image above on Vectric's user forum HERE.
Details on making the vectors and setting up the toolpath on my blog article.
4D