GD&T Profile Tolerancing Applications 3 — Questions and Answers
Question 1: A composite profile tolerance uses two segments in the feature control frame. What does the upper segment control?
- Feature-to-feature relationship (pattern location)
- Location of the pattern relative to the datums (Correct answer)
- Form of individual surfaces only
- Size of the feature
Correct answer: Location of the pattern relative to the datums
In a composite profile tolerance, the upper segment (PLTZF) controls the location of the entire pattern relative to the datum reference frame.
Question 2: For a composite profile tolerance, the lower segment feature-relating tolerance zone framework (FRTZF) primarily controls:
- Location of the pattern from the datums
- Size of the feature
- The relationship of features within the pattern to each other (Correct answer)
- The profile form tolerance
Correct answer: The relationship of features within the pattern to each other
The FRTZF (lower segment) controls the feature-to-feature relationship within the pattern, ensuring features are correctly spaced relative to one another.
Question 3: Which statement is TRUE about Profile of a Line vs. Profile of a Surface?
- Profile of a line controls the entire 3D surface; profile of a surface controls a 2D cross-section
- Profile of a line controls individual cross-sectional elements; profile of a surface controls the entire surface (Correct answer)
- They are interchangeable and mean the same thing
- Profile of a line always requires more datums than profile of a surface
Correct answer: Profile of a line controls individual cross-sectional elements; profile of a surface controls the entire surface
Profile of a line controls each individual cross-sectional line element of a surface, while profile of a surface controls the entire surface simultaneously.
Question 4: When specifying a non-uniform profile tolerance using ASME Y14.5-2018, which notation is used?
- NON-UNI placed before the tolerance value in the feature control frame (Correct answer)
- A separate feature control frame for each zone width
- Two separate leader lines from the feature control frame
- The abbreviation NU placed after the datum references
Correct answer: NON-UNI placed before the tolerance value in the feature control frame
ASME Y14.5-2018 introduced the NON-UNI modifier placed before the tolerance value to indicate a non-uniform profile tolerance zone.
Question 5: A profile of a surface callout with a tolerance of 0.5 and datums A and B means the surface must lie between two boundaries how far apart?
- 0.25 mm each side (total 0.5 mm)
- 0.5 mm apart (0.25 each side for bilateral) (Correct answer)
- 1.0 mm apart
- Depends on the surface curvature
Correct answer: 0.5 mm apart (0.25 each side for bilateral)
A bilateral profile tolerance of 0.5 creates a zone 0.5 mm wide total, with boundaries 0.25 mm on each side of the true profile.
Question 6: Profile tolerancing is most commonly used instead of coordinate tolerancing when:
- The part has only flat surfaces and sharp corners
- The part has complex curved or freeform surfaces that cannot be defined by simple ± dimensions (Correct answer)
- The part requires very loose tolerances
- The part is made of plastic materials only
Correct answer: The part has complex curved or freeform surfaces that cannot be defined by simple ± dimensions
Profile tolerancing excels at controlling complex curved or freeform surfaces where traditional ± coordinate dimensions would be ambiguous or impractical.
Question 7: Which of the following best describes how the true profile is defined for a profile tolerance?
- By the actual measured part surface
- By the basic dimensions shown on the drawing (Correct answer)
- By the tolerance zone midpoint
- By averaging the measured surface points
Correct answer: By the basic dimensions shown on the drawing
The true profile is defined by the basic (theoretically exact) dimensions shown on the drawing, from which the tolerance zone boundaries are offset.
GD&T Profile Tolerancing Applications 3
A composite profile tolerance uses two segments in the feature control frame.
What does the upper segment control?