GD&T Symbols and Rules 3 — Questions and Answers
Question 1: What does the 'free state' symbol (circle with the letter F) indicate in a GD&T callout?
- The tolerance applies after release from manufacturing fixturing (Correct answer)
- The part must be inspected while clamped
- The feature is a free-turning axis
- The tolerance applies only at room temperature
Correct answer: The tolerance applies after release from manufacturing fixturing
The free state modifier indicates that the geometric tolerance applies to the part in its unconstrained, free state — not held in a fixture.
Question 2: A profile of a line tolerance differs from a profile of a surface tolerance in that it:
- Controls only a cross-sectional slice at any given location (Correct answer)
- Controls the entire 3D surface simultaneously
- Requires two datum references
- Only applies to cylindrical features
Correct answer: Controls only a cross-sectional slice at any given location
Profile of a line controls the shape of a cross-sectional profile at individual cross-sections, while profile of a surface controls the complete 3D form.
Question 3: In a feature control frame, the compartment immediately following the tolerance value compartment contains:
- The primary datum reference (Correct answer)
- The geometric characteristic symbol
- The material condition modifier for the tolerance
- The bonus tolerance value
Correct answer: The primary datum reference
After the tolerance value (and any modifier on it), the next compartments list datum references in order: primary, secondary, then tertiary.
Question 4: Which symbol, when placed below a feature control frame, indicates that the tolerance applies to the entire length or surface — not per unit?
- No additional symbol is needed; it applies to the entire extent by default (Correct answer)
- An 'E' modifier in the frame
- An underline beneath the frame
- The 'T' symbol for total
Correct answer: No additional symbol is needed; it applies to the entire extent by default
By default, a geometric tolerance applies to the full extent of the feature unless a 'per unit' basis is specified separately below the frame.
Question 5: Which of the following is NOT a valid runout tolerance symbol in ASME Y14.5?
- Total Runout of a Plane Surface (Correct answer)
- Circular Runout
- Total Runout
- Runout of a Conical Surface
Correct answer: Total Runout of a Plane Surface
There is no separate GD&T symbol called 'Total Runout of a Plane Surface'; Total Runout (the arrow symbol) covers cylindrical and planar surfaces within one symbol.
Question 6: The diameter symbol (ø) placed before a tolerance value in a feature control frame means the tolerance zone is:
- Cylindrical (Correct answer)
- Equal in all directions on a flat plane
- A width between two parallel lines
- Spherical
Correct answer: Cylindrical
When ø precedes the tolerance value, the tolerance zone is a cylinder of that diameter surrounding the true axis or center.
Question 7: According to ASME Y14.5, which rule governs the relationship between size tolerance and form tolerance for an individual feature of size?
- Rule #1 (Envelope Principle) (Correct answer)
- Rule #2 (RFS Default)
- Rule #3 (Datum Precedence)
- Rule #4 (Virtual Condition)
Correct answer: Rule #1 (Envelope Principle)
Rule #1 (the Envelope Principle) states that the form of an individual feature of size must be within a perfect geometric envelope at MMC.
GD&T Symbols and Rules 3
What does the 'free state' symbol (circle with the letter F) indicate in a GD&T callout?