CDT CDT Geometric Dimensioning & Tolerancing 2 — Questions and Answers
Question 1: What is the purpose of a feature control frame in GD&T?
- To show the part's material specification
- To convey the geometric tolerance for a feature (Correct answer)
- To indicate the machining process required
- To display the revision history of the drawing
Correct answer: To convey the geometric tolerance for a feature
A feature control frame is a rectangular box on a drawing that communicates the type of geometric control, tolerance value, and applicable datums for a feature.
Question 2: Which condition describes when a feature of size contains the least amount of material within its tolerance?
- Maximum Material Condition (MMC)
- Least Material Condition (LMC) (Correct answer)
- Regardless of Feature Size (RFS)
- Virtual Condition (VC)
Correct answer: Least Material Condition (LMC)
Least Material Condition (LMC) is the condition where a feature contains the minimum amount of material, such as the smallest shaft or largest hole within tolerance.
Question 3: Runout tolerance is always measured with the part:
- Clamped in a vise
- Rotating about a datum axis (Correct answer)
- Held in a free state
- Fixed to a surface plate
Correct answer: Rotating about a datum axis
Runout is a composite control measured by rotating the part about the specified datum axis while a dial indicator contacts the controlled surface.
Question 4: What is the difference between circular runout and total runout?
- Circular runout applies to flat surfaces; total runout applies to cylinders
- Circular runout is measured at individual cross-sections; total runout covers the entire surface (Correct answer)
- Circular runout uses two datums; total runout uses one
- There is no practical difference between them
Correct answer: Circular runout is measured at individual cross-sections; total runout covers the entire surface
Circular runout controls variation at each individual cross-section independently, while total runout controls the entire surface simultaneously during full rotation.
Question 5: Which GD&T symbol controls the taper or cone shape of a feature relative to a datum axis?
- Parallelism
- Angularity (Correct answer)
- Conicity
- Cylindricity
Correct answer: Angularity
Angularity controls the orientation of a surface or axis at a specified angle (other than 0° or 90°) relative to a datum.
Question 6: When a GD&T symbol appears in a drawing without a datum reference, which controls can be applied independently without a datum?
- Position and runout
- Form controls such as flatness, straightness, circularity, and cylindricity (Correct answer)
- Orientation controls such as parallelism and angularity
- Profile controls only when applied to planes
Correct answer: Form controls such as flatness, straightness, circularity, and cylindricity
Form controls (flatness, straightness, circularity, cylindricity) control the shape of a feature intrinsically and do not require a datum reference.
CDT CDT Geometric Dimensioning & Tolerancing 2
What is the purpose of a feature control frame in GD&T?