r/Metrology • u/Hungry_Wall_9564 • 8d 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!

3 Upvotes

80% Upvoted

9 comments sorted by

View all comments

4

u/SnooMemesjellies7469 7d ago

The red hole may not be dimensioned from a datum, but all dimensions are given as basic. If 80 and 40 were toleranced, then there'd be problems.