GD&T Tolerance zone

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

Categories: : GD & Tolerancing