Thats old school craziness using a Gauge pin or anything that is hard to set a Tool or to check a Tool set height, you damage the cutting edges of the cutter by using this technique
Machine some aluminum or hard plastic blocks and use that, to check large Tool offsets or plastic shim down to 007" works very well and is much more forgiving than any hard metal, just rubbing a Gauge Pin or a Gauge Block damages the Cutter the first touch, Plastic is the best Aluminum at a push
Your Clearance Plane is wherever you want to park the Z axis after an operation, you are making things more complicated than they have to be