GD&T Composite Feature Control 2 — Questions and Answers
Question 1: In a composite feature control frame, the upper segment is called the:
- Feature-Relating Tolerance (FRT)
- Feature Level Control (FLC)
- Feature Control Tolerance Zone (FCTZ)
- Pattern-Locating Tolerance Zone Framework (PLTZF) (Correct answer)
Correct answer: Pattern-Locating Tolerance Zone Framework (PLTZF)
The upper segment of a composite feature control frame is called the Pattern-Locating Tolerance Zone Framework (PLTZF), which controls the location of the pattern as a whole.
Question 2: Which datum references are typically included in the Feature-Relating Tolerance Zone Framework (FRTZF) of a composite callout?
- All datums from the PLTZF
- Only orientation datums, no location datums (Correct answer)
- No datums at all
- Additional datums not in the PLTZF
Correct answer: Only orientation datums, no location datums
The FRTZF typically references only orientation datums (like datum A for perpendicularity) but not location datums, since it controls feature-to-feature relationships rather than absolute location.
Question 3: A composite positional tolerance has PLTZF of ⌀0.8 and FRTZF of ⌀0.3. What does ⌀0.3 control?
- The location of the pattern from datums B and C
- The spacing between individual features within the pattern (Correct answer)
- The size tolerance of each feature
- The perpendicularity of each feature to datum A only
Correct answer: The spacing between individual features within the pattern
The FRTZF tolerance of ⌀0.3 controls the spacing and orientation of features relative to each other within the pattern.
Question 4: Can a composite feature control frame be used with profile of a surface tolerances?
- No, composite frames are only valid for position tolerances
- Yes, composite profile tolerances are explicitly defined in ASME Y14.5 (Correct answer)
- Yes, but only for internal features
- No, profile uses bilateral tolerances exclusively
Correct answer: Yes, composite profile tolerances are explicitly defined in ASME Y14.5
ASME Y14.5 explicitly defines composite profile tolerances, where the upper segment controls location and the lower segment controls form, orientation, and feature-to-feature relationships.
Question 5: When a datum reference is repeated in both the PLTZF and FRTZF of a composite callout, what does it mean in the lower segment?
- It has no effect in the lower segment
- It restricts the FRTZF from translating relative to that datum (Correct answer)
- It doubles the tolerance value
- It applies the tolerance to that datum feature only
Correct answer: It restricts the FRTZF from translating relative to that datum
When a datum is repeated in the FRTZF, it restricts translation of the tolerance zone relative to that datum while still allowing the zone to shift in other directions.
Question 6: Two single-segment position callouts differ from a composite callout because:
- Two single-segment callouts cannot reference the same datums
- Each segment of a two single-segment callout independently locates features from its referenced datums (Correct answer)
- Two single-segment callouts always have larger tolerances
- Two single-segment callouts apply only to patterns of two features
Correct answer: Each segment of a two single-segment callout independently locates features from its referenced datums
In a two single-segment callout, each segment independently locates features from its own datum references, whereas the FRTZF in a composite callout controls only feature-to-feature relationships.
Question 7: In composite tolerancing, which condition must always be true regarding the PLTZF and FRTZF tolerance values?
- FRTZF must be larger than PLTZF
- PLTZF must be larger than or equal to FRTZF (Correct answer)
- Both tolerance zones must be equal
- PLTZF applies only at MMC
Correct answer: PLTZF must be larger than or equal to FRTZF
The PLTZF tolerance must always be equal to or larger than the FRTZF tolerance, since the FRTZF zone must fit within the PLTZF zone.
GD&T Composite Feature Control 2
In a composite feature control frame, the upper segment is called the: