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
Reason 4: Inspection and Design Interpret the Drawing Differently
If Design and Quality regularly debate what a tolerance “really means,” your GD&T may lack clarity – or there may be an issue with proper understanding within your teams.
A Couple of GD&T Tips to Review
Don’t Be Tricky with GD&T 2009
Don’t Confuse Dimensioning with Tolerancing - 2009
Reason 5: Directly Toleranced Dimensions are used to Control Location or Orientation Instead of GD&T
If location and orientation are controlled with directly toleranced dimensions instead of using geometric tolerances, your team will be creating ambiguous specifications. This means part suppliers will be able to measure the parts in more than one way. The measurement option the supplier will choose for each of these tolerances will be the one that makes the results look good, rather than the one that addresses part function.
A Couple of GD&T Tips to Review
Stop Locating Features with +/- Toleranced Dimensions
If the Drawing Doesn’t Use GD&T--Run
Time to Stop the Nonsense
Reason 6: GD&T is being Used, but Tolerances are Extremely Tight
Overly tight tolerances drive up cost. Overly loose tolerances create functional failures.
Both often indicate guesswork rather than functional analysis. A tolerance analysis course for the design group, and GD&T fundamentals courses for all, will provide methods that enable looser tolerances for manufacturing.
A Couple of GD&T Tips to Review
Don’t Be Tricky with GD&T
Don’t Confuse Dimensioning with Tolerancing
Use Profile to Open up Your Tolerances - 1994
Use Profile to Open up Your Tolerances - 2009
Use Profile to Open up Your Tolerances - 2018