GD&T Profile Tolerancing Applications 5 — Questions and Answers
Question 1: In ASME Y14.5, when profile of a surface is used with the Ⓜ (MMC) modifier on a datum reference, what does this enable?
- The profile tolerance value increases as the datum departs from MMC
- Bonus tolerance is granted to the profile
- The profile zone shifts location as the datum feature departs from MMC (Correct answer)
- Profile tolerances can never use MMC modifiers on datums
Correct answer: The profile zone shifts location as the datum feature departs from MMC
When the MMC modifier is applied to a datum reference in a profile callout, the datum reference frame can shift as the datum feature departs from MMC, allowing the profile zone to translate.
Question 2: A part drawing shows a profile of a surface tolerance callout with a value of 1.0 and the note 'EACH ELEMENT.' This means:
- The entire surface must lie within a 1.0 mm zone
- Each individual line cross-section must lie within 1.0 mm, but adjacent sections need not relate to each other (Correct answer)
- The tolerance applies to every part in the lot
- Each surface element has a 1.0 mm flatness requirement
Correct answer: Each individual line cross-section must lie within 1.0 mm, but adjacent sections need not relate to each other
The 'each element' note effectively converts the control to a profile-of-a-line behavior, where each cross-sectional slice must meet the tolerance independently.
Question 3: What is the tolerance zone shape for a profile of a line tolerance applied to a straight line element?
- Two coaxial cylinders
- Two parallel straight lines (a 2D band) (Correct answer)
- A spherical zone
- Two parallel curved lines offset from the true line
Correct answer: Two parallel straight lines (a 2D band)
For a straight line element, the profile of a line tolerance zone is a 2D band formed by two parallel straight lines separated by the tolerance value.
Question 4: When profile tolerancing is applied to an airfoil or turbine blade surface, which aspect makes profile essential over traditional GD&T controls?
- Airfoils only have flat surfaces that flatness cannot handle
- The complex curvature that varies continuously requires a single tolerance to govern the true aerodynamic profile (Correct answer)
- Profile is cheaper to inspect than other methods
- Airfoils use metric units exclusively, requiring profile
Correct answer: The complex curvature that varies continuously requires a single tolerance to govern the true aerodynamic profile
Continuously varying complex aerodynamic curvature cannot be adequately controlled with individual size, form, or location tolerances; profile tolerancing defines the entire true surface in one control.
Question 5: The simultaneous requirement rule in GD&T means that profile tolerances sharing the same datum reference frame are gauged:
- Independently, one at a time
- Simultaneously in a single setup without repositioning the part (Correct answer)
- Only if they reference identical tolerance values
- Using different datum reference frames for each check
Correct answer: Simultaneously in a single setup without repositioning the part
Simultaneous requirements means multiple profile (or other) tolerances sharing the same DRF must be verified in a single setup without moving the part, ensuring mutual consistency.
Question 6: A profile of a surface callout with the value '0.3' and an additional circle 'U' modifier followed by '0.1' in ASME Y14.5-2018 indicates:
- A uniform zone of 0.3 with a 0.1 flatness refinement
- An unequally disposed zone: 0.1 outside and 0.2 inside the true profile (totaling 0.3) (Correct answer)
- A unilateral zone of 0.1 entirely outside the true profile
- Two separate profile tolerances of 0.3 and 0.1
Correct answer: An unequally disposed zone: 0.1 outside and 0.2 inside the true profile (totaling 0.3)
The U modifier with value 0.1 specifies that 0.1 of the total 0.3 zone lies outside the true profile and the remaining 0.2 lies inside, creating an unequally disposed bilateral zone.
Question 7: Which statement correctly describes how profile of a surface interacts with Rule #1 (the Envelope Principle)?
- Profile of a surface automatically invokes Rule #1 for all surfaces it controls
- Profile of a surface overrides Rule #1; the surface must only satisfy the profile zone, not the perfect-form envelope (Correct answer)
- Profile and Rule #1 always produce identical requirements
- Rule #1 only applies when profile is used with MMC modifier
Correct answer: Profile of a surface overrides Rule #1; the surface must only satisfy the profile zone, not the perfect-form envelope
Profile of a surface supersedes Rule #1 (the envelope principle) — the controlled surface must fall within the profile tolerance zone, not necessarily within a perfect-form envelope at MMC.
GD&T Profile Tolerancing Applications 5
In ASME Y14.5, when profile of a surface is used with the Ⓜ (MMC) modifier on a datum reference, what does this enable?