Print calls a plane Datum A , Datum B is a rectangular 2x4 pattern of holes thru plane A.
then there are a bunch of other features that call TP to A and B.
Searching the forum I figured out how to do a best fit alignment.
I'm stuck on how to set holes as B with DATDEF for use in a true position dimension (using Xactmeasure, PCDMIS 2016).
How can those 8 holes be a datum? I can see a bolt hole circle being a datum. And what they really are looking for is perpendicularity. But you have to give them a true position for both the top and bottom of those holes back to -A-
Er, why?
Why do you imagine a bolt circle be a datum, and not any other pattern of holes?
If the mating part has a flat face which sits against A and eight studs which locate through those holes it's perfectly valid.
Also it's not just checking perpendicularity, it's checking the relationship of the holes to each other.
Imagine an assembly with various electrical components in which are connected by wires. You need to ensure the mounting holes for each component are right to each other (so the component can be affixed) but the relationship between each component isn't that critical, because the wires take up any slack/misalignment.
How can those 8 holes be a datum? I can see a bolt hole circle being a datum. And what they really are looking for is perpendicularity. But you have to give them a true position for both the top and bottom of those holes back to -A-
Er, why?
Why do you imagine a bolt circle be a datum, and not any other pattern of holes?
If the mating part has a flat face which sits against A and eight studs which locate through those holes it's perfectly valid.
Also it's not just checking perpendicularity, it's checking the relationship of the holes to each other.
Imagine an assembly with various electrical components in which are connected by wires. You need to ensure the mounting holes for each component are right to each other (so the component can be affixed) but the relationship between each component isn't that critical, because the wires take up any slack/misalignment.
