1. How many holes are there for any basic size?
a) 22
b) 24
c) 26
d) 28
Explanation: There are 28 different holes for any basic size. These are designated by capital letters. A, B, CD, C, D, E, EF, F, FG, G, H, JS, J, K, M, N, P, R, S, T, U, V, X, Y, Z, ZA, ZB, ZC these are the 28 holes.
2. What does ES represent in terminology as per IS: 919?
a) Lower deviation of hole
b) Upper deviation of shaft
c) Lower deviation of shaft
d) Upper deviation of hole
Explanation: ‘ES’ and ‘es’ represents upper deviation for hole and shaft respectively. ‘EI’ and ‘ei’ represents lower deviation for hole and shaft respectively.
3. What is ‘IT01’?
a) Basic size of hole
b) Basic size of shaft
c) Tolerance grade
d) Standard tolerance factor
Explanation: ‘IT’ refers to the standard tolerance which belongs to any standard grade of tolerance. Tolerance grades are designated by ‘IT’ letters followed by a number. For example, IT01 is a tolerance grade.
4. For tolerance grades 5 to 16, what is the formula for standard tolerance factor?
(D=mean diameter in mm)
a) 0.45 (D)1/3 + 0.001D
b) 10*D
c) 0.45 (D)3 + 0.001 D
d) 20*D
Explanation: For tolerance grades 5 to 16 the value of tolerance magnitude is in terms of standard tolerance factor, i = 0.45 (D)1/3 + 0.001 D. For grade IT6, tolerance is 10i. Above it, at each 5th step the tolerance magnitude is multiplied by 10.
5. What is the hole size which is covered by IT05?
a) 500 mm
b) 600 mm
c) 700 mm
d) 800 mm
Explanation: There are 7 finest tolerance grades from 1T01 to IT05. It covers sizes up to 500 mm. There are 11 coarsest grades which cover sizes up to 3150 mm. Tolerance grades depend upon shaft or hole size.
6. Which of the following is not true for hole and shaft basis systems?
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 the 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.
7. Which of the following grade of a hole is mostly used for non-circular fits?
a) H5
b) H6
c) H7
d) H9
Explanation: H9, H5, H6, H7 these all are the grades of a 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.
8. 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.
9. 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.
10. Which grades are available in shaft ’j’ assembly?
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 require less clearance than ‘h’ and also where a slight interference is permitted. It can be used in gear rings clamped to steel hubs.