Geometric Dimensioning and Tolerancing (GD&T) is a standardized system used to define and control the geometry of parts in engineering drawings. GD&T symbols are grouped into five main categories:
1. Form
Controls the shape of a feature, independent of its location or orientation.
- Straightness
- Flatness
- Circularity (Roundness)
- Cylindricity
👉 Ensures features have the correct shape.
2. Orientation
Controls the tilt or angle of a feature relative to a datum.
- Parallelism
- Perpendicularity
- Angularity
👉 Ensures features are properly aligned.
3. Location
Controls the position of features relative to datums.
- Position
- Concentricity
- Symmetry
👉 Ensures features are in the correct place.
4. Profile
Controls the outline or surface of a feature.
- Profile of a Line
- Profile of a Surface
👉 Ensures complex shapes match design intent.
5. Runout
Controls variation when a part rotates.
- Circular Runout
- Total Runout
👉 Ensures smooth rotation and minimal wobble.
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