Establishing datum on angled surfaces

[HunterS1103]

hello all,

My boss and I have a question and it is at what angle are you not allowed to use a pad as a point for a datum?? For example we have 4 net pads that being used 2 of which are as parallel as they can be to the surface plate, and the other 2 are angled. So we just need to know is there a cut off for when it can't be used as datum or is there no limit which angle it can be at as long as it's not perpendicular to the first two points? Thanks in advance for time and help answering the question.

[gibsonridge]

i wouldn't use that as a primary leveling datum ,depending on where you take your point (high-low) is going to affect your 3 point level