ASME ASME Geometric Dimensioning and Tolerancing 2 — Questions and Answers
Question 1: What does 'true position' mean in ASME Y14.5 GD&T?
- The actual measured position of a feature
- The theoretically exact location of a feature defined by basic dimensions (Correct answer)
- The tolerance zone center for runout
- The datum axis of a cylindrical feature
Correct answer: The theoretically exact location of a feature defined by basic dimensions
True position is the theoretically exact location of a feature, defined by basic (boxed) dimensions from the datum reference frame.
Question 2: Which symbol is used in GD&T to control the circular cross-section of a cylinder at any cross-section?
- Cylindricity
- Circularity (roundness) (Correct answer)
- Runout
- Concentricity
Correct answer: Circularity (roundness)
Circularity (roundness) controls each circular cross-section of a cylinder independently, requiring all points to lie within an annular zone.
Question 3: Under ASME Y14.5, what is a 'basic dimension'?
- A dimension with no tolerance
- A theoretically exact value from which toleranced dimensions are established (Correct answer)
- The nominal design size of a feature
- A reference dimension shown in parentheses
Correct answer: A theoretically exact value from which toleranced dimensions are established
A basic dimension is a theoretically exact value, enclosed in a box, used to establish the true position or profile of a feature; tolerances come from the feature control frame.
Question 4: What geometric characteristic is used to control both size and form of a complete cylindrical feature?
- Circularity
- Straightness
- Cylindricity (Correct answer)
- Runout
Correct answer: Cylindricity
Cylindricity controls the form of an entire cylindrical surface, requiring all points to lie between two coaxial cylinders, combining roundness, straightness, and taper.
Question 5: In GD&T, 'total runout' controls which combination of errors?
- Circularity and surface finish
- Concentricity and size variation
- All surface variations relative to a datum axis including wobble, taper, and form (Correct answer)
- Only wobble during rotation
Correct answer: All surface variations relative to a datum axis including wobble, taper, and form
Total runout measures all surface deviations — including circular runout, taper, straightness, and form — across the entire surface relative to the datum axis.
Question 6: What does the term 'regardless of feature size' (RFS) mean in ASME Y14.5?
- The tolerance applies only at MMC
- The geometric tolerance applies at any produced size of the feature without bonus tolerance (Correct answer)
- The tolerance zone increases as the part gets smaller
- Only form tolerances apply
Correct answer: The geometric tolerance applies at any produced size of the feature without bonus tolerance
RFS means the stated geometric tolerance applies regardless of the actual produced size of the feature — no bonus tolerance is gained.
ASME ASME Geometric Dimensioning and Tolerancing 2
What does 'true position' mean in ASME Y14.5 GD&T?