GD&T Tolerance zone

Mufaddal Rasheed Author

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:

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