Drawing help (Again)

I have been asked to take a look at a drawing to see if I understand them. They look pretty simple but there is one thing which is giving me a bit of trouble.

A this point I am only guessing that I would have to align to the points 'a', 'b', 'c' & 'd'. Usually in this situation I would have X,Y&Z data for these points if that was to be the case and it would be made obvious what they are for.

I will only show this of the part as it doesn't show anything really, but 'a' is a mid point between two opposing holes on the other side of the part and the rest seem to be constructed from this midpoint with reference dimensions. Has anyone seen this style of print before? is this a legitimate way of creating the datum system?

UKCMM over 7 years ago

Points ' b ' 'c ' and 'd ' are target points as I see it and point ' a ' is used to position the target points. There should be a note on the drawing as to what the points are used for and how they relate to the datum setup of the part. The target zone should be stated and may be in the general workmanship/drafting standards of the customer.
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bigtallanddopey over 7 years ago in reply to UKCMM

I have found a note saying that these are gauge target points. Nothing on how they relate to the datum setup of the part. Maybe there is something hidden away in a standard or something. And there isn't a target zone stated anywhere either.

I am wondering if it is hidden away in the catia file which I cannot access.

I was going to just ask the customer but they're on shutdown now for a few weeks.
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UKCMM over 7 years ago in reply to UKCMM

The target points should be used to set a datum plane, as to the zone they are normally quite large and 6mm / 1/4 inch seems to be the norm on castings / sheet metal.
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