What does GD&T stand for in blueprint reading?

• A. Global Dimensioning and Timing
• B. Graphical Design and Tolerances
• C. Geometric Dimensioning and Tolerancing
• D. General Dimensions and Tolerances

Answer: (C)

Geometric Dimensioning and Tolerancing is the standardized language used on engineering drawings to specify how much a feature’s size, shape, and its orientation and location may vary. It goes beyond simple numeric dimensions by using geometric symbols to control form (like straightness or flatness), orientation (perpendicularity, angularity), location (true position), and runout, all tied to reference datums. This system ensures parts from different suppliers will fit and function together because everyone reads the same rules and applies the same limits.

On a blueprint you’ll see feature control frames with geometric symbols and datums that communicate these tolerances precisely. For example, a true position tolerance shows how far a hole's center can deviate from its intended location relative to datum features, which is crucial for assemblies.

The other options don’t match how blueprint reading is taught. They use terms that aren’t the standard terminology for this language, and they don’t convey the specific concept of controlling geometry and its allowable variation across features and datums.