GD&T Profile Tolerancing Applications 4 — Questions and Answers
Question 1: When a profile of a surface tolerance is used to control a flat planar surface (instead of flatness), what additional control does profile provide over flatness?
- Profile controls form only, same as flatness
- Profile can also control orientation and location when datums are referenced (Correct answer)
- Profile requires more measurement points than flatness
- Profile only applies to curved surfaces, not flat ones
Correct answer: Profile can also control orientation and location when datums are referenced
Unlike flatness (form only), profile of a surface with datum references can simultaneously control the orientation and location of a flat surface in addition to its form.
Question 2: A profile tolerance zone that is defined as entirely OUTSIDE the true profile (unilateral-outward) would be specified using ASME Y14.5-2018 by:
- Adding a UZ modifier with the offset value (Correct answer)
- Writing 'OUTSIDE' in the feature control frame
- Placing two zeros separated by a slash before the tolerance value
- Adding the symbol for unilateral tolerance after the datum
Correct answer: Adding a UZ modifier with the offset value
In ASME Y14.5-2018, the UZ (Unequally Disposed Zone) modifier with an offset value specifies where the profile tolerance zone is positioned relative to the true profile.
Question 3: In the context of profile tolerancing, what does 'between' notation (using the symbol ↔ or the word BETWEEN) indicate?
- The tolerance applies between two datum planes
- The profile tolerance applies only to the portion of the surface between two specified points or features (Correct answer)
- The tolerance is split equally between two surfaces
- The profile tolerance uses bilateral distribution
Correct answer: The profile tolerance applies only to the portion of the surface between two specified points or features
The 'between' notation limits the profile tolerance application to a specific portion of the surface, bounded by two designated points or features.
Question 4: Which inspection method is most suitable for verifying a complex profile tolerance on a freeform surface?
- Go/no-go gauge
- Micrometer measurement at key points
- Coordinate Measuring Machine (CMM) with CAD model comparison (Correct answer)
- Surface roughness tester
Correct answer: Coordinate Measuring Machine (CMM) with CAD model comparison
A CMM compared against a CAD model is the most effective method for verifying complex freeform profile tolerances because it captures the full 3D surface geometry.
Question 5: If a profile of a surface tolerance references only Datum A (a plane), which degrees of freedom does it constrain?
- All six degrees of freedom
- Translation perpendicular to Datum A only
- Three translational degrees of freedom
- Translation perpendicular to A and two rotational degrees of freedom (tilts relative to A) (Correct answer)
Correct answer: Translation perpendicular to A and two rotational degrees of freedom (tilts relative to A)
A single planar datum A constrains translation perpendicular to it plus rotation about two axes (pitch and roll relative to the plane), leaving translation along A and rotation about A's normal free.
Question 6: A profile tolerance applied to a conical surface primarily replaces which combination of traditional tolerances?
- Perpendicularity and flatness
- Angularity and cylindricity (Correct answer)
- Straightness and circularity
- Parallelism and position
Correct answer: Angularity and cylindricity
Profile of a surface on a cone effectively controls both the angle (similar to angularity) and the roundness/form (similar to cylindricity) of the conical surface simultaneously.
Question 7: When a single profile of a surface tolerance simultaneously controls an entire part with complex geometry, this approach is sometimes called:
- Universal tolerancing
- Single-segment composite profile
- Profile with all-over application (Correct answer)
- Simultaneous requirement profile
Correct answer: Profile with all-over application
Applying profile of a surface 'all over' (indicated by two concentric circles) controls the entire part's surface geometry with a single tolerance specification.
GD&T Profile Tolerancing Applications 4
When a profile of a surface tolerance is used to control a flat planar surface (instead of flatness), what additional control does profile provide over flatness?