You're asking a question that really cant be answered...... A hole for bearing isn't ( probably be scanned ) the same as a hole for a pipe that would would be welded in ( 3 hits ) ...... You need a variable to calculate the infinite amount of variables needed for all possibilities.
Some companies cover parameter settings with work instructions, or standard operating procedures, or some other similar documents. They define how many points to take for each feature based on the type, size, tolerance, etc. Technically my work place has such work instructions, but they weren't written well so us CMM programmers just ignore them and muddle through.
Unfortunately, we are transitioning from a manager who's motto was to make the programs as simple and fast running as possible to a new manager who's motto is to be as thorough as possible. To further complicate the matter, each of our customers have different expectations as well. It's always a guessing game trying to predict what will make everyone happy, or at least make everyone appeased.
There is an international standard called AUKOM that is being taught. To help CMM programmer keep those kinds of things in order. There is an ISO standard for FORM measring on a diameter. I have a widget I made to calculate # of hits, Speed and Gaussian filter setting.
There's a rule which says : min number of hits = 3*(number of hits to define a feature)
So 9 for a plane or circle, 12 for a sphere, 15 for a cylinder, 18 for a cone.
This rule is applied only for location and size, not for the form.
For the depht, I usually set it to zero, because I don't use CAD, it helps me to avoid some crashes on closed holes...
