LMC and MMB? Notice the last letter of each acronym ("C" vs "B"). These are two fundamentally different concepts. If the last letter of the acronym is a "C", the modifier is applied to a feature (of size). If the last letter of the acronym is a "B", the modifier is applied to a datum feature.
You cannot use a material modifier on a feature when specifying a profile tolerance because the tolerance zone surrounds the surface, which has no size at any given point. You can apply a modifier on a datum feature reference if it is a feature of size when specifying a profile tolerance.
As far as position is concerned, you cannot apply a material modifier on a feature if it is not a feature of size. Technically, you cannot specify a position tolerance at all if it is not a feature of size.
Great explanation. This is why I don't bother with MMB/LMB when checking profile because there is just no size of this at all. As far as I'm aware MMB/LMB is used to build fixtures to inspect functionality of the parts. We have to be aware that folks, especially newbies from big shot schools, who dump GD&T on prints have little understanding what they are doing. At my place this is normal. That is why I do 3 things. One is I ignore things, two I request assembly CAD or paper print & three I go to manufacturing engineering for more info on the manufacturing/fabrication process they decide to proceed with. Based on this information I build CMM programs.
