GD&T Composite Feature Control 4 — Questions and Answers
Question 1: An MMC modifier is applied to the FRTZF of a composite position callout. What benefit does this provide?
- It allows the PLTZF to increase
- It provides bonus tolerance for feature-to-feature location as features depart from MMC (Correct answer)
- It eliminates the need for the PLTZF
- It restricts the tolerance to the minimum material condition only
Correct answer: It provides bonus tolerance for feature-to-feature location as features depart from MMC
An MMC modifier on the FRTZF allows each feature's tolerance zone to increase (bonus tolerance) as the feature departs from MMC, while still maintaining pattern geometry.
Question 2: A composite callout has PLTZF|A|B|C and FRTZF|A|B. Compared to FRTZF|A only, what additional constraint does adding datum B impose?
- Restricts translation perpendicular to datum B
- Restricts rotation about the axis perpendicular to datum B
- Restricts rotation about the datum B axis (Correct answer)
- Removes all translational freedom from the FRTZF
Correct answer: Restricts rotation about the datum B axis
Adding datum B (typically a secondary datum) to the FRTZF restricts the rotational degree of freedom about the axis perpendicular to datum B, locking the pattern's clocking.
Question 3: For a pattern of four holes using composite position, how many total cylindrical tolerance zones must each physical hole simultaneously satisfy?
- One
- Two (Correct answer)
- Four
- Eight
Correct answer: Two
Each physical hole must satisfy two cylindrical tolerance zones simultaneously: one from the PLTZF and one from the FRTZF.
Question 4: In ASME Y14.5-2018, which symbol is used to indicate 'Separately' when the simultaneous requirement should NOT apply to composite callouts on the same drawing?
- SIM
- SEP (Correct answer)
- SQ
- ISO
Correct answer: SEP
The notation 'SEP REQT' (Separately) is added to indicate that multiple geometric tolerances referencing the same DRF should be verified independently rather than simultaneously.
Question 5: A composite positional tolerance controls a pattern of slots. The FRTZF is wider than the individual slot tolerance zone. This situation is:
- Valid because the FRTZF overrides the size tolerance
- Invalid because the FRTZF cannot exceed the pattern size tolerance
- Valid if MMC modifier is used
- Invalid because the FRTZF must always be smaller than the PLTZF (Correct answer)
Correct answer: Invalid because the FRTZF must always be smaller than the PLTZF
The FRTZF tolerance must always be equal to or smaller than the PLTZF tolerance, since the FRTZF zones must fit within the PLTZF framework.
Question 6: Which of the following best describes the 'float' allowed by the FRTZF in composite tolerancing?
- Each individual feature zone floats independently within the PLTZF
- The entire FRTZF pattern of zones shifts as a rigid group within the PLTZF zones (Correct answer)
- Features can rotate individually within the FRTZF zones
- The FRTZF zones expand to accommodate manufacturing variation
Correct answer: The entire FRTZF pattern of zones shifts as a rigid group within the PLTZF zones
The FRTZF tolerance zone framework shifts and (if no orientation datums are cited) rotates as a rigid group, maintaining the pattern geometry while accommodating location variation.
Question 7: When verifying composite position with a functional gauge, which segment drives the gauge hole locations?
- The FRTZF always drives gauge hole locations
- The PLTZF drives the absolute pattern location; a separate gauge checks FRTZF (Correct answer)
- Both segments are checked with a single gauge simultaneously
- The gauge only verifies the larger of the two tolerances
Correct answer: The PLTZF drives the absolute pattern location; a separate gauge checks FRTZF
A PLTZF functional gauge locates holes at true position relative to the datum reference frame; a separate FRTZF gauge checks the feature-to-feature geometry with holes at the FRTZF tolerance size.
GD&T Composite Feature Control 4
An MMC modifier is applied to the FRTZF of a composite position callout.
What benefit does this provide?