GD&T Tolerances & Fits in Engineering Drawings 2 — Questions and Answers
Question 1: A shaft is specified as ⌀50 -0.010/-0.030. What is the maximum shaft diameter?
- 49.970 mm
- 50.000 mm
- 49.990 mm (Correct answer)
- 50.010 mm
Correct answer: 49.990 mm
The upper deviation is -0.010, so maximum shaft diameter = 50.000 - 0.010 = 49.990 mm.
Question 2: Which ANSI/ISO fit system uses the hole as the fixed reference with H designation?
- Shaft-basis system
- Hole-basis system (Correct answer)
- Bilateral tolerance system
- Unilateral tolerance system
Correct answer: Hole-basis system
In the hole-basis system, the hole deviation is fixed (H) and the shaft deviation varies to achieve the desired fit.
Question 3: A clearance fit is achieved when the minimum clearance between mating parts is:
- Negative
- Zero
- Positive (Correct answer)
- Equal to the tolerance
Correct answer: Positive
A clearance fit always has a positive minimum clearance, meaning the shaft is always smaller than the hole.
Question 4: What does the term 'allowance' refer to in tolerance and fit terminology?
- The total tolerance range of both parts
- The minimum clearance or maximum interference between mating parts (Correct answer)
- The difference between upper and lower deviations
- The nominal size of the feature
Correct answer: The minimum clearance or maximum interference between mating parts
Allowance is the intentional difference between mating parts — minimum clearance for clearance fits or maximum interference for interference fits.
Question 5: A hole tolerance is specified as ⌀25 H7. If H7 corresponds to +0.021/0.000, what is the minimum hole diameter?
- 25.021 mm
- 24.979 mm
- 25.000 mm (Correct answer)
- 24.000 mm
Correct answer: 25.000 mm
For H-designation holes, the lower deviation is always zero, so minimum hole diameter equals the nominal size of 25.000 mm.
Question 6: Which type of tolerance expression shows deviation equally in both directions from nominal?
- Unilateral tolerance
- Limit dimensioning
- Bilateral tolerance (Correct answer)
- Referenced tolerance
Correct answer: Bilateral tolerance
A bilateral tolerance distributes the allowable variation equally on both sides of the nominal value, such as 25.00 ± 0.05.
Question 7: In an interference fit, which condition is always true at maximum material condition (MMC)?
- Clearance is maximized
- Clearance equals zero
- Interference is maximized (Correct answer)
- Interference is minimized
Correct answer: Interference is maximized
At MMC — largest shaft and smallest hole — interference is at its maximum value in an interference fit.
GD&T Tolerances & Fits in Engineering Drawings 2
A shaft is specified as ⌀50 -0.010/-0.030.
What is the maximum shaft diameter?