In this series, we highlight 11 common signs that teams may not be getting the full value from GD&T. Each sign is based on real-world situations we regularly see in engineering, manufacturing, and inspection environments.
For every example, we’ll break down what’s happening, why it matters, and share practical GD&T tips from Tec-Ease to help improve clarity, strengthen communication, and drive better results.
If any of these signs sound familiar, it may be time for a Complete GD&T tune-up — whether that means applying a few targeted tips, utilizing the GD&T Reference Center or investing in more comprehensive training.
You Might Need Complete GD&T Training If...
Reason 1: You’re Using GD&T Symbols Without Fully Understanding the Tolerance Zone
If team members can name the symbol but struggle to sketch or explain the tolerance zone, and the feature element that must be within the tolerance zone, that’s a red flag.
Misuse often happens when people memorize symbols without understanding how they work, and what they control.
A Couple of GD&T Tips to Review
Stabilizing the Zone 2009
Projected Tolerance 1994 & 2009
Projected Tolerance 2018
Reason 2: Everything Has a Profile Tolerance
Profile is powerful—but it’s not the answer for every situation.
If profile is being used as a “catch-all” instead of selecting the appropriate geometric tolerance that provides just the control needed for part function, and no more, then the tolerance specifications will not be as simple, intuitive, and readable as they should be.
A Couple of GD&T Tips to Review
Don’t Be Tricky with GD&T 2009
Apply Profile of a Surface to Surface 1994
Reason 3: Datum Features Are Most Often Chosen Based on Manufacturing or Inspection Considerations, Not Function
Datum features should reflect how the part functions and assembles—not what’s easiest to measure or fixture and not just based on the features that manufacturing uses in their set-ups.
Datum features selected based on anything other than functional considerations will introduce tolerance stacks, which may lead to a need to specify tolerances that are twice as tight, just to deal with those tolerance stacks. There are times when overall considerations will make manufacturing or inspection-based datum features the best choice, but they will be the exception, rather than the rule.
A Couple of GD&T Tips to Review
Datum Features Based Upon Function 1994
Primary Datum Features Surface Control - 1994, 2009 & 2018