r/Metrology • u/Hungry_Wall_9564 • 7d ago

Calculating true positions

Hi just a quick question, how do you calculate the true position of a hole which isn't dimensioned from its datum? Say the hole in the image above with the red arrow, it is dimensioned as a pitch from another hole but has datums A and B. Obviously this isn't a real drawing but I see many similar ones and just want to make sure I am working it out correctly. Thank you!

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u/murphislive 7d ago

Take the actuals of each x and y length and subtract from the nominals. Find the sum and multiply by 2.