I'm looking for some advice in regards to the following image, I drew this up quickly so apologies if it is a little messy, it is in metric and I am working to BS8888. Here is my take on it:

Datum [B] is controlled as a group, origin can be established at the centre of the group or any of the holes within the group defined by the theoretical exact dimensions? In this instance I believe datum [B] holes can be best fit then output to 0.025 true position from the centre of the group to each hole, this would effectively be 0.05 between pitch? Would the TED's be ignored in the pitch and over ruled by this, or would you say the pitch had to be held to 0.025 between holes as the [110] and [110] TED's illustrate?

Datum [A][B] become a fully constraint datum system controlling all degrees of freedom, 3 by datum [A] and 3 by datum [B] part rotation is constraint by the TED's using a best fit? Datum [G] hole is controlled to [A][B] and fully defined?

The 2 remaining holes are the ones I am not totally sure on. Would I be correct to say this is the correct datum precedence in regards to the TED's? Datum [A] 3 degrees of freedom, datum [G] would control 2 DOF becoming the origin point, then datum [B] as a group would control the last DOF being the rotation and orientation within their respective TED's? (best fit) I have read about creating hole groups as a feature set but I haven't used that method in alignments and unsure how they would behave.

Hole group datum.jpg

I would be appreciative of any helpful input or advice, thanks in advance..

Datum [B] is controlled as a group, origin can be established at the centre of the group or any of the holes within the group defined by the theoretical exact dimensions? In this instance I believe datum [B] holes can be best fit then output to 0.025 true position from the centre of the group to each hole, this would effectively be 0.05 between pitch? Would the TED's be ignored in the pitch and over ruled by this, or would you say the pitch had to be held to 0.025 between holes as the [110] and [110] TED's illustrate?

Datum [A][B] become a fully constraint datum system controlling all degrees of freedom, 3 by datum [A] and 3 by datum [B] part rotation is constraint by the TED's using a best fit? Datum [G] hole is controlled to [A][B] and fully defined?

The 2 remaining holes are the ones I am not totally sure on. Would I be correct to say this is the correct datum precedence in regards to the TED's? Datum [A] 3 degrees of freedom, datum [G] would control 2 DOF becoming the origin point, then datum [B] as a group would control the last DOF being the rotation and orientation within their respective TED's? (best fit) I have read about creating hole groups as a feature set but I haven't used that method in alignments and unsure how they would behave.

Hole group datum.jpg

I would be appreciative of any helpful input or advice, thanks in advance..

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