This set of Engineering Metrology Questions and Answers for Freshers focuses on “Guide for Selection of Fits”.
a) Hole basis system is generally preferred over shaft basis system
b) Shaft basis system can be used when products are made from bright drawn bars
c) Choice of system depends upon nature of the product
d) In hole basis system, allowances are applied to the hole
Explanation: Hole basis system is preferred because it is easy to produce a shaft with specified tolerances than hole. In hole basis system, all tolerances are applied to shaft and hole size is taken as basic size.
2. Which of the following grade of hole is mostly used for non-circular fits?
Explanation: H9, H5, H6, H7 these all are the grades of hole. H9 can be obtained by reaming and boring. It is used for non-circular fits. H5 can be obtained by honing or internal grinding. H7 can be produced by broaching and grinding.
3. Which of the following option is incorrect for clearance fits?
a) Shaft ‘a’ gives a large clearance
b) Shaft ‘n’ is used for clearance fits
c) Shaft ‘d’ can be used for loose pulleys
d) Shaft ‘g’ is expensive to manufacture
Explanation: Shaft ‘n’ gives transition fit. It gives clearance to only extreme sizes. It is recommended for tight fits. Grades 5, 6 and 7 are available. Shafts a, b and c gives clearance fit. They all gives large clearance so they are not widely used.
4. What is the range of shafts which produce transition fits?
a) Shaft ‘a’ to ‘h’
b) Shaft ‘e’ to ‘n’
c) Shaft ‘d’ to ‘h’
d) Shaft ‘j’ to ‘n’
Explanation: ‘a’ to ‘h’ shafts produces clearance fits with H7 basic hole. ‘j’ to ‘n’ produce transition fit with H7 basic size. Transition fits may result in either interference or clearance fit. It will depend upon the actual size of tolerance of mating component.
a) 1 to 5
b) 2 to 6
c) 3 to 7
d) 5 to 11
Explanation: Shaft ‘j’ is a transition fit and available in grades 5 to 11. It is good for location fits which requires less clearance than ‘h’ and also where a slight interference is permitted. It can be used in gear rings clamped to steel hubs.
6. Which of the following grade is never used for fits?
Explanation: H5, H6, H7, H8, H9, H10, H11 these are the hole grades. H10 is not used for diameter fits. It can be used for milled widths. H11 is never used for fits because this grade is very coarse. H11 is useful only for coarse punched holes or drilled holes.
7. Which of the option is correct about preference of shaft and holes in machine tool industries?
a) ‘A11’ is of first preference in shafts
b) ‘B9’ is of first preference in holes
c) ‘c2’ is of first preference in shafts
d) ‘b11’ is of second preference in holes
Explanation: a11, c2, d9, d11, e8 etc. are the first preference for shafts and b9, b11, c8, c11, d8 etc. are the second preferences for shafts. First preference of holes are A11, D11, E11, F7, F8 etc. and B9, B11, C9, C11, D9 etc. are the second preferences for holes.
8. Which of the following option is correct for given statements regarding selection of fits?
Statement 1: Shaft ‘h’ is an interference fit and used only for running parts.
Statement 2: Shaft ‘k’ is the true transition fit.
a) T, F
b) F, F
c) T, T
d) F, T
Explanation: Shaft ‘h’ gives clearance fit and available in grades 5 to 11. It is useful for spigot fits. Shaft ‘k’ is a transition fit and it is best suited for location fits. Grades available for this category are also 5 to 11.
a) Shaft ‘s’
b) Shaft ‘f’
c) Shaft ‘b’
d) Shaft ‘t’
Explanation: Shaft ‘s’ gives interference fit. It is used for semi-permanent or permanent assemblies of cast iron and steel members. It can be used for valve shafting’s and collar pressed on the shaft.
10. Which of the following gives interference fit?
a) Shaft ‘n’
b) Shaft ‘p’
c) Shaft ‘m’
d) Shaft ‘g’
Explanation: Shaft ‘p’ gives a true interference fit and available in grades 6 or 7. With hole of grade 8 it behaves as transition fit. It is a standard fit for cast iron and steel. It can be used for fixing of a bush on a gear. Shaft ‘g’ gives clearance fit. Shaft ‘m’ and ‘n’ gives transition fit.
Sanfoundry Global Education & Learning Series – Engineering Metrology.
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