Engineering Metrology Questions and Answers – Diameter and Pitch Combinations

This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Diameter and Pitch Combinations”.

1. What is the range of diameters that have been specified in IS: 4218 (Part II)-1976?
a) 1-50mm
b) 1-500mm
c) 1-250mm
d) 1-100mm

Explanation: The diameter and pitch combinations for ISO Metric screw threads in the diameter range of 1 to 500 mm have been specified in the IS: 4218 (Part II)—1976. This standard specifies several pitches for various diameters.

2. According to IS: 4218 (Part II)-1976, How many types of pitches are present?
a) 2
b) 1
c) 4
d) 3

Explanation: According to this IS: 4218 (Part II)-1976, there are two types of pitches i.e. coarse series and fine series. For any diameter in study, coarse pitch is the largest of the pitches associated with that diameter (it has nothing to do with quality), the rest of the pitches being always finer than the coarse pitch are called fine pitches.

3. How many choices for diameters are present in IS: 4218 (Part II)-1976?
a) 1
b) 2
c) 3
d) 4

Explanation: IS: 4218 (Part II)-1976 gives three choices for diameters i.e. first choice, second choice and third choice, and recommends the use of diameters given in the first choice as far as possible for various applications.

4. How many tolerance grades are there for ISO metric screw threads?
a) 4
b) 5
c) 6
d) 7

Explanation: On ISO metric threads, tolerances are defined by tolerance position and tolerance grades. There are 7 tolerance grades and these are 3, 4, 5, 6, 7, 8, and 9. 3, 4 and 5 are for precision threads and 6 for medium quality and for less precision methods are 7, 8 and 9.

5. For a diameter of 20mm, several pitches given are 1, 1.5, 2 and 2.5mm. Which of the following is coarse pitch?
a) 1mm
b) 2 and 2.5mm
c) 1.5, 2 and 2.5mm
d) 2.5mm

Explanation: For the diameter of 20 mm various pitches allowed are 1, 1.5, 2 and 2.5 mm. Of these 2.5 is coarse pitch, and the 1, 1.5 and 2 are fine pitches. Only largest of the pitches falls under coarse pitch and other remaining comes under fine pitches.
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6. What is the symbol designated for the pitch diameter combination of an ISO Metric screw thread by IS: 4218 (Part II)-1976?
a) M
b) PD
c) DP
d) P

Explanation: According to this IS: 4218 (Part II)-1976, the pitch diameter combination of an ISO Metric screw thread is designated by the letter M followed by the values of the nominal thread diameter and the pitch(expressed in mm).

7. What is the correct way to write pitch diameter combination of thread size 20mm and pitch 2.5mm?
a) M 20:2.5
b) M {20,2.5}
c) M 20×2.5
d) M 20-2.5

Explanation: While the designation of pitch diameter combination of screw thread, letter M is followed by the values of the nominal thread diameter and the pitch, (in mm) the two being separated by the sign ‘x’. Hence, combination of thread size 20mm and pitch 2.5mm is shown by M 20×2.5.

8. What should M 22 designate in pitch diameter combination?
a) 22mm diameter with lowest fine pitch
b) 22mm diameter with standard coarse pitch
c) 22mm diameter with highest fine pitch
d) 22mm diameter with all pitch

Explanation: When no pitch is mentioned in the designation of pitch diameter combination, it means standard coarse pitch is implied e.g., M 22 shall designate a pitch diameter combination of threads size 22 mm and coarse pitch of 2.5 mm.

9. Which of the following is the first choice of diameter which is indicated by IS?
a) 20
b) 18
c) 17
d) 22

Explanation: The first choice of diameters which are indicated by IS are 1,1.2,1.6,2,2.5,3,4,5,6,8,10,12,16, 20,24, 30, 36, 42, 48, 56, 64, 72, 80, 90, 100, 110, 125, 140, 160,180, 200, 220, 250 and 280.

10. Which of the following tolerance grades can be used for minor diameter and pitch diameter of internal threads?
a) 4, 6, 8
b) 3, 4, 5, 6, 7
c) 3, 4, 5
d) 4, 5, 6, 7, 8

Explanation: The tolerance grades recommended for minor diameter and pitch of internal threads are 4, 5, 6, 7, and 8 and for major diameter of external threads and for pitch diameter of external threads are 4, 6, 8 and 3, 4, 5, 6, 7, 8, 9 respectively.

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