Engineering Metrology Questions and Answers – Tolerances

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Tolerances”.

1. What are the functional dimensions?
a) Have to be machined and fit with other mating components
b) Which have no effect on the performance of quality
c) Need not to be machined to an accuracy of the high degree
d) Function is more important than accuracy

Explanation: Non-functional dimensions have no effect on the performance of quality of the assembly or component. Non-functional dimensions need not to be machined to higher accuracy.

2. Why tolerances are given to the parts?
a) Because it’s impossible to make perfect settings
b) To reduce weight of the component
c) To reduce cost of the assembly
d) To reduce amount of material used

Explanation: Tolerances are provided to the parts because variations in the material properties introduce errors and production machines themselves have inherent inaccuracies. Another reason to introduce tolerance is that it is not possible to make perfect settings by operator so some tolerances are provided.

3. What is bilateral tolerance?
a) Total tolerance is in 1 direction only
b) Total tolerance is in both the directions
c) May or may not be in one direction
d) Tolerance provided all over the component body

Explanation: Total tolerance is specified on both the sides of the basic dimension. This usually have + and – tolerance of equal amount.

4. Which type of tolerance provided in drilling mostly?
a) Bilateral
b) Unilateral
c) Trilateral
d) Compound

Explanation: Mostly unilateral tolerance is provided in drilling as dimension is allowed to vary in one direction only. Hole is always oversize, not undersize.

5. What is mean clearance?
a) Maximum size of hole minus maximum size of shaft
b) Minimum size of hole minus minimum size of shaft
c) Mean size of hole minus mean size of shaft
d) Average of both size of shaft and hole

Explanation: Statistical approach allows wider tolerances compared to complete interchangeability approach. Methods used by statistical approach are usually permits cheaper production. Mean clearance is equal to (mean size of hole – mean size of shaft).
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6. Which of the following is incorrect about tolerances?
a) Too loose tolerance results in less cost
b) Tolerance is a compromise between accuracy and ability
c) Too tight tolerance may result in excessive cost
d) Fit between mating components is decided by functional requirements

Explanation: Loose tolerance results in increase in cost, assembly problems and poor performance of the product. Tight tolerance results in unnecessary machining and inspection time.

7. Quality control charts doesn’t depend on which factor?
a) Normal distribution
b) Random sampling
c) Independence between samples
d) Binomial distribution

Explanation: In establishing of realistic specifications, control charts are considered as a good guide for the design office. Quality control charts are based on the assumptions of random sampling and normal distribution.

8. Which of the following option is true for given statements?
Statement 1: Bilateral tolerances are used in mass production techniques.
Statement 2: The basic size should be equal to upper and lower limits.
a) T, T
b) F, F
c) T, F
d) F, T

Explanation: Bilateral tolerances are preferred in mass production techniques where setting of a machine is done for the basic size. If unilateral tolerances are specified in place of bilateral, then basic size should be changed to make it bilateral. Basic size is in half way between lower and upper limits.

9. If a clearance fit is present between shaft and hole, what is the tolerance on shaft or hole for a complete interchangeable approach?
a) ½ of maximum clearance – ½ of minimum clearance
b) ¼ of maximum clearance – ¼ of minimum clearance
c) Maximum clearance – minimum clearance
d) ¾ of maximum clearance – ¾ of minimum clearance

Explanation: There are two approaches for deciding of tolerances and shafts i.e. statistical and complete interchangeable approach. There is no risk is taken about a single non-conforming assembly in complete interchangeable approach.

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