4.24.12 Secondary Datum Axis
For MMB, the centering method used to establish the datum axis has a set of three equally spaced features set at a fixed radial distance based on the MMB.
Regarding fig 4-53:
Question: Should I understand that if B had been callout at MMB in the positional callout (and maybe in the profile callout) then a perpendicularity on Ø.170 ± 0.1 outside diameter to datum feature A is needed?
Otherwise how to calculate the MMB requested on the above paragraph, if the orientation relationship between B and A is missing?
But, on the other hand, as far as I can see, in general when datum targets are used no such a relationship (between primary and / or secondary/ tertiary) is needed.
Therefore, no perpendicularity needed if B is RMB and perpendicularity is required if B is MMB? Is my understanding correct?