GD&T Tolerance zone
Mufaddal Rasheed 
What is the meaning of a tolerance zone in GD&T ? how are tolerance zones defined for various geometric controls.
Tolerance zone in GD&T :
- Tolerance zones are an important concept in GD&T . Understanding of tolerance zone is the first step in interpretation of a GD&T control applied to a feature through a feature control frame.
- Each feature control frame has one or more tolerance zone attached to it
- Adding the dia symbol before geometric tolerance in feature control frame means that he tolerance zone is cylindrical in shape.
- Each geometric control will have associated tolerance zone and tolerance zone maybe fixed with respect to datums or it maybe freely floating depends on the geometric control applied
- For form control like Flatness the tolerance zone is generally a prismatic shape as shown
Here is an example of tolerance zone for a perpendicularity control applied to a side face.
The size of the tolerance zones are exaggerated to show the shape .
Here is an example with positional tolerance applied to a hole.
It is a Cylindrical tolerance zone.
Tolerance zone for Profile tolerance:
Learn more about Tolerance zones in GD&T from this 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