GD&T Tolerances & Fits in Engineering Drawings 5 — Questions and Answers
Question 1: Which condition produces maximum clearance in a clearance fit?
- Largest shaft with smallest hole
- Smallest shaft with largest hole (Correct answer)
- Both parts at nominal size
- Both parts at MMC
Correct answer: Smallest shaft with largest hole
Maximum clearance occurs when the shaft is at its smallest (LMC) and the hole is at its largest (LMC), giving the most play.
Question 2: A drawing note states 'ALL TOLERANCES ±0.005 UNLESS OTHERWISE SPECIFIED.' A dimension shown as 3.750 +0.010/−0.000 would have which tolerance applied?
- ±0.005 from the title block
- +0.010/−0.000 as shown on the dimension (Correct answer)
- ±0.010 from averaging both
- +0.005/−0.000 combined
Correct answer: +0.010/−0.000 as shown on the dimension
A specific tolerance shown on a dimension always overrides the general title block tolerance for that particular feature.
Question 3: What is the purpose of using a running and sliding fit (RC fit) classification in ANSI B4.1?
- To ensure permanent assembly with no relative motion
- To provide controlled clearance for parts that move relative to each other (Correct answer)
- To allow press-fit assembly without lubrication
- To define surface finish requirements for mating parts
Correct answer: To provide controlled clearance for parts that move relative to each other
RC (Running and Clearance) fits are designed to provide controlled clearance allowing relative motion between assembled parts.
Question 4: When converting between unilateral and bilateral tolerance expressions, a dimension of 25.00 +0.06/−0.00 is equivalent to:
- 25.03 ± 0.03 (Correct answer)
- 25.06 ± 0.06
- 25.00 ± 0.06
- 25.03 ± 0.06
Correct answer: 25.03 ± 0.03
The midpoint is 25.00 + 0.03 = 25.03, and the equal bilateral deviation is ±0.03, giving 25.03 ± 0.03.
Question 5: In a virtual condition analysis, the virtual condition of an external feature (pin) at MMC with a straightness tolerance of 0.01 mm is:
- MMC diameter minus the straightness tolerance
- MMC diameter plus the straightness tolerance (Correct answer)
- LMC diameter plus the straightness tolerance
- Nominal diameter plus the straightness tolerance
Correct answer: MMC diameter plus the straightness tolerance
Virtual condition for an external feature = MMC size + applicable geometric tolerance, representing the worst-case boundary.
Question 6: A locational clearance fit (LC fit) is characterized by:
- Guaranteed interference at all conditions
- Snug fits for stationary parts with small clearance (Correct answer)
- Large clearance for free-running assemblies
- Transition between clearance and interference
Correct answer: Snug fits for stationary parts with small clearance
LC (Locational Clearance) fits provide snug to small clearances for stationary parts that need accurate location but are not designed to run.
Question 7: Which of the following best describes how tolerances are verified during inspection using a go/no-go gauge?
- The GO gauge checks the LMC boundary; the NO-GO gauge checks the MMC boundary
- The GO gauge checks the MMC boundary; the NO-GO gauge checks the LMC boundary (Correct answer)
- Both gauges check the nominal size from different directions
- The GO gauge checks roundness; the NO-GO gauge checks diameter
Correct answer: The GO gauge checks the MMC boundary; the NO-GO gauge checks the LMC boundary
The GO gauge must pass through (checking the MMC limit), while the NO-GO gauge must not pass through (checking the LMC limit).
GD&T Tolerances & Fits in Engineering Drawings 5
Which condition produces maximum clearance in a clearance fit?