Learning to effectively use and troubleshoot geometric dimensioning and tolerancing (GD&T) analysis can be a saving grace when you’re faced with the question, “Why did my check fail?”

This article will explain the fundamental principles of GD&T evaluation and provide practices to visualize and troubleshoot your results. It will also help clarify the requirements of two standards: ISO 1101—“Geometrical product specifications (GPS),” which defines the fundamentals for geometrical tolerancing; and ASME Y14.5—“Dimensioning and tolerancing,” which is considered the authoritative guideline for the design language of GD&T.

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