GD&T Symbols and Rules 2 — Questions and Answers
Question 1: Which GD&T symbol is used to control the orientation of a surface relative to a datum plane without controlling its location?
- Parallelism (Correct answer)
- Position
- Flatness
- Profile of a Surface
Correct answer: Parallelism
Parallelism controls the orientation of a surface or axis to be parallel to a datum without specifying its exact location.
Question 2: What does the 'S' modifier inside a feature control frame signify?
- Statistical tolerancing
- Spherical diameter (Correct answer)
- Surface condition
- Symmetrical tolerance
Correct answer: Spherical diameter
The 'S' prefix before a diameter symbol (Sø) indicates a spherical diameter in GD&T.
Question 3: Rule #2 in ASME Y14.5 states that unless otherwise specified, each tolerance of orientation, form, location, or runout applies to which condition?
- Regardless of Feature Size (RFS) (Correct answer)
- Maximum Material Condition (MMC)
- Least Material Condition (LMC)
- Free State (FST)
Correct answer: Regardless of Feature Size (RFS)
Rule #2 (RFS) is the default condition — geometric tolerances apply regardless of actual feature size unless MMC or LMC is specified.
Question 4: Which symbol in a feature control frame indicates that a tolerance applies to the full surface profile, including both sides of the tolerance zone equally?
- Equal bilateral profile (no modifier) (Correct answer)
- Unequal bilateral profile with 'U' symbol
- All Around symbol
- All Over symbol
Correct answer: Equal bilateral profile (no modifier)
A profile tolerance with no modifier defaults to equal bilateral disposition, split equally inside and outside the true profile.
Question 5: The 'all around' symbol on a leader line in a profile tolerance callout is represented by:
- A circle at the bend of the leader line (Correct answer)
- An arrow at both ends of the leader
- The letters 'AR' in the feature control frame
- A double-headed arrow on the leader
Correct answer: A circle at the bend of the leader line
A circle placed at the junction of the leader line and the reference line indicates that the profile tolerance applies all around the cross-section.
Question 6: In GD&T, what is the purpose of the datum feature symbol (a rectangle with a triangle)?
- To identify a feature that serves as an origin for measurements (Correct answer)
- To indicate a tolerance zone shape
- To specify a material condition modifier
- To denote a reference dimension
Correct answer: To identify a feature that serves as an origin for measurements
The datum feature symbol identifies physical features on a part that establish the coordinate system used for measurements and inspections.
Question 7: Which of the following GD&T symbols controls both the form and the orientation of a surface with respect to a datum?
- Angularity (Correct answer)
- Flatness
- Straightness
- Circularity
Correct answer: Angularity
Angularity controls the orientation of a surface or axis at a specified angle to a datum, inherently also controlling form within the tolerance zone.
GD&T Symbols and Rules 2
Which GD&T symbol is used to control the orientation of a surface relative to a datum plane without controlling its location?