GD&T Perpendicularity
Mufaddal Rasheed 
What is Perpendicularity in GD&T under orientation control? What does it mean and how to interpret the callout?
Perpendicularity is the condition of a surface, axis, or centre plane that is at a
90◦ angle to a datum plane or datum feature of size axis
Example of a part on which perpendicularity GD&T callout is used .
The tolerance zone formed is nothing but a prismatic rectangle at 90 degree angle to the datum feature surface and with a width of 0.02 mm .
Every point on the selected feature should lie within a band of 0.02 which is perpendicular to a datum.
Inspection of Perpendicularity:
One way of inspecting perpendicularity of this part is placing it on a guage block (blue ) and then bringing another gauge block in contact with the surface to be inspected . The gauge block in brown is square with the base gauge block (blue)
Then a wire of diameter 0.02 mm is inserted into the gap between the part surface and gauge block face. IF the wire goes inside then that means the perpendicularity is not acceptable.
Example of perpendicularity applied to feature of size (hole) :
Here the tolerance zone is a cylinder with diameter of 0.1 mm.
Learn more about how to Interpret GD&T callouts from this Free e-book on GD&T interpretations
To learn more about GD&T have a look at this course
Geometric Dimensioning and Tolerancing: Basics
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Categories: : GD & Tolerancing