How to interpret the meaning of a GD&T callout on a pattern of features? What are the tolerance zones like?
When there are multiple features in a pattern then the meaning of the GD&T scheme changes
Here is an example:
Simplifies the GD&T drawing avoids repetitive annotations
Example no 2 shows a rectangular pattern of holes
A manufactured part with exaggerated form is shown here . the four plus signs indicate the centres of holes and the datum reference frame is show as the co ordinate system at top right edge of part .
Analytical definition of tolerance zones :
Each tolerance zone is a circle and those circles are locating a distance with respect to the origin which is the origin of datum reference frame.
Hence by finding the equations for each circle we can arrive the condition to satisfy each tolerance zone requirement.
These are the equations of each tolerance zone with the condition for acceptance.
If we have a measured manufactured actual part and replace x and y values then the equations should be satisfied for acceptance.