For the best results, optical switches are recognised to be more accurate than micro switches. The photos  shows one made to the design show in project -Acknowledgments section (RF45 mill conversion).

 

They are quite easy to make. I glued two photo sensors together and mounted them on small slice of Vero board, they also have led lights which are on, to show they are working.

 

When the 1/4 shafts are pushed, a spade is pushed out the sensors, allowing the light to fall on the photo sensors, triggering a stop.  Springs return them back to the centre position. On the z axis I have use a pre- built sensor from  cnc4pc , see parts and suppliers section.