GD&T Composite Feature Control 3 — Questions and Answers
Question 1: A bolt pattern uses composite position with PLTZF ⌀1.0|A|B|C and FRTZF ⌀0.4|A. What does datum A control in the FRTZF?
- Location along the A datum plane
- Perpendicularity (orientation) of each hole to datum A (Correct answer)
- The true position of the entire pattern
- The size of the tolerance zone
Correct answer: Perpendicularity (orientation) of each hole to datum A
In the FRTZF, datum A (a flat surface) controls only the orientation (perpendicularity) of each hole relative to datum A, not the hole pattern's location.
Question 2: What is the key geometric difference between the PLTZF and FRTZF tolerance zones?
- PLTZF zones are cylindrical; FRTZF zones are spherical
- PLTZF zones are fixed in space relative to datums; FRTZF zones can translate as a group (Correct answer)
- PLTZF zones apply at LMC; FRTZF zones apply at MMC
- PLTZF uses unilateral tolerance; FRTZF uses bilateral tolerance
Correct answer: PLTZF zones are fixed in space relative to datums; FRTZF zones can translate as a group
The PLTZF zones are located at true position relative to the datum reference frame, while the FRTZF zones can translate as a group but must maintain their internal pattern geometry.
Question 3: The simultaneous requirement applies to composite position tolerances when:
- The same datum reference frame is shared and no SEP notation is used (Correct answer)
- MMC modifier is applied to the PLTZF
- The FRTZF references more datums than the PLTZF
- A cylindrical tolerance zone is specified
Correct answer: The same datum reference frame is shared and no SEP notation is used
The simultaneous requirement applies when multiple position callouts reference the same datum reference frame without the SEP (Separately) notation, meaning they must be verified in the same setup.
Question 4: How many tolerance zones exist for each feature in a composite position callout with both PLTZF and FRTZF?
- One combined zone
- Two separate zones — one from each segment (Correct answer)
- Three zones — size, location, and orientation
- Four zones — one per datum referenced
Correct answer: Two separate zones — one from each segment
Each feature must simultaneously satisfy two tolerance zones: the larger PLTZF zone (which locates the pattern) and the smaller FRTZF zone (which controls feature-to-feature relationships).
Question 5: In composite profile of a surface, what does the lower segment control compared to the upper segment?
- Profile size tolerance only
- Profile form, orientation, and feature-to-feature location (but not absolute location) (Correct answer)
- Surface finish requirements
- The material condition of the surface
Correct answer: Profile form, orientation, and feature-to-feature location (but not absolute location)
The lower segment of composite profile controls form, orientation, and the relationship between features, but the tolerance zone can translate/rotate relative to the datum reference frame.
Question 6: What happens to the FRTZF tolerance zone framework if no orientation datums are referenced in it?
- The FRTZF is invalid and must reference at least one datum
- The FRTZF zones are free to rotate and translate relative to the DRF (Correct answer)
- The FRTZF defaults to the same datums as the PLTZF
- The FRTZF applies only at the true position of each feature
Correct answer: The FRTZF zones are free to rotate and translate relative to the DRF
If no datums are cited in the FRTZF, the tolerance zone framework is free to translate and rotate in any direction, only constrained to maintain the pattern geometry internally.
Question 7: Which scenario correctly describes when composite tolerancing provides an advantage over a single position callout?
- When only one feature is being controlled
- When the pattern location relative to datums can be loose, but feature-to-feature spacing must be tight (Correct answer)
- When all features must be at the same absolute location
- When the part has no orientation requirements
Correct answer: When the pattern location relative to datums can be loose, but feature-to-feature spacing must be tight
Composite tolerancing is advantageous when the overall pattern location can have a larger tolerance while the individual feature spacing within the pattern must be held to a tighter tolerance.
GD&T Composite Feature Control 3
A bolt pattern uses composite position with PLTZF ⌀1.0|A|B|C and FRTZF ⌀0.4|A.
What does datum A control in the FRTZF?