Geometric Dimension & Tolerancing

A: 6.60 mm is the boundary that matters. Virtual condition for an internal feature equals MMC size plus the full positional tolerance, not half and not ignored. Anything smaller than Ø6.60 mm risks bolt interference at worst case.

A: Primary datum selection is the tripwire. A painted external face as datum A allows compliant inspection while breaking assembly alignment; functional mounting pads belong at the top of the datum hierarchy.

A: 0.07 mm is enough to break marginal tolerances. Aluminum expands roughly 23 µm/m·K, so over 0.3 m and 10 K the math lands right there, and many CMMs won't fix it unless told.

A: 0.02 mm is the scrap driver. Position already controls orientation and location of the bore axis; adding tight flatness on the face often adds cost without protecting any failure mode.