This set of Engineering Metrology Multiple Choice Questions & Answers (MCQs) focuses on “Micrometers”.
1. What is the least count of a micrometer?
a) 0.01 mm
b) 0.02 mm
c) 0.1 mm
d) 0.2 mm
Explanation: Least count can be calculated by “Pitch divided by no. of divisions on a circular scale”.
2. What is the use of ratchet stop in micrometer?
a) Prevent motion of spindle
b) Maintain uniform measuring pressure
c) Provide measuring surface
d) Forms measuring tip
Explanation: Ratchet stop is present at the end of thimble cap to maintain a uniform measuring pressure. By ratchet stop standard conditions of measurement are attained.
3. Which of the following is incorrect about micrometer?
a) Thimble and barrel should have a dull finish
b) Total travel of the measuring spindle is called measuring range
c) Graduated surface diameter of barrel should be 5 mm
d) Screw has 10 or 20 threads per cm
Explanation: Thimble and barrel should have a dull finish for ease of reading. Graduated surface diameter of the barrel should not be less than 10 mm.
4. What is the hardness of measuring faces of anvil and spindle?
a) 800 HV
b) 600 HV
c) 1000 HV
d) 100 HV
Explanation: Measuring faces of anvil and spindle has a hardness of about 800 HV or 62 HRC. Faces may be tipped with tungsten carbide.
5. What is the total error in micrometer?
a) Positive and negative deviation from the zero point
b) Error in parallelism
c) Deviation from measurement of a nominal dimension
d) Maximum difference between ordinates of cumulative error
Explanation: Cumulative error is the deviation of measurement from a nominal dimension. It includes errors like thread errors, errors of measuring faces etc. Maximum difference between ordinates of cumulative error is the total error.
6. How many divisions are graduated on thimble?
Explanation: Graduation lines should be clearly engraved. 50 divisions are graduated on thimble each representing 0.01mm.
7. Which of the following option is correct about given statements about micrometer?
Statement 1: The anvil should not protrude from the frame.
Statement 2: An adjusting nut is present in micrometer to compensate wear
a) Only statement 1 is true
b) Only statement 2 is true
c) Both the statements are true
d) Both the statements are false
Explanation: The anvil is fixed and should protrude at least 3 mm. It is to permit the attachment of measuring wire support. Adjusting nut is present between spindle and nut’s screw portion. It is provided for adjusting the zero setting and to compensate wear on the measuring faces.
8. What is the value of total error for grade 1 micrometer when micrometer is tested at 20oC?
Explanation: Total error should not exceed 4+(L/100)µ m for ‘grade 1’ micrometer and 10+(L/50)µm for ‘grade 2’ micrometer when tested at 20oC.
9. Which of the following is correct about micrometer?
a) Plastic insulating grips are used on the frame
b) Satin chrome finish increase the reading errors
c) A uniform and maximum measuring force is applied
d) Barrel is the removable part of the frame
Explanation: Plastic insulated grips are employed on the frame to reduce heat transfer. Satin chrome finish minimize the reading errors and eliminate glare. A uniform and minimum measuring force should be applied to reduce error.
10. To check the bending in micrometer, what is the difference between the measurement of loaded and unloaded conditions for micrometer range 0 to 25 mm?
a) 1.5 µm per kg
b) 2.0 µm per kg
c) 2.5 µm per kg
d) 3.0 µm per kg
Explanation: In loaded and unloaded conditions, Difference between measurements should not exceed 1.5µm, 2µm, 2.5µm and 3µm per kg for the range 0 to 25, 25 to 50, 50 to 75 and 100 mm respectively.
11. Which of the following option is true for the given statements about micrometer?
Statement 1: There is a fixed spindle and a rotated anvil.
Statement 2: For taking the reading, micrometer dimension is set slightly larger than part size.
a) T, F
b) F, F
c) F, T
d) T, T
Explanation: Spindle is not fixed infact for good results spindle should move freely. Anvil is fixed generally but sometimes anvil is accommodated in reamed hole and a thread extension is provided.
12. Which of the following is incorrect about precautions in using a micrometer?
a) Final movement is given by ratchet
b) Thimble is turned till the Measuring tip just touches the part to be measured
c) Part to be measured is held in right hand and micrometer in left hand for good results
d) Error is reading is may be due to lack of flatness of anvil
Explanation: The part to be measured must be in left hand and micrometer in the right hand for better results. Place small finger and adjoining finger in the U frame. Middle finger supports micrometer and forefinger and thumb are placed near the thimble. This is the correct way of using a micrometer.
13. What is the accuracy range of stick micrometers?
a) ±0.005 mm
b) ±0.05 mm
d) ±0.0005 mm
Explanation: Accuracy of stick micrometers is of the order of ±0.005 mm. They are used to measure longer internal lengths. They have a series of extension rods to measure up to maximum length.
14. Which of the following is incorrect?
a) V-Anvil micrometer caliper is used to check out of roundness
b) Blade type micrometer has a non-rotating spindle
c) Tube wall thickness can be measured by an ordinary micrometer
d) Self-centering inside micrometer has an interchangeable measuring head
Explanation: An ordinary micrometer can’t be used for measuring tube wall thickness because of the concavity of internal surfaces. For this, anvil is made of cylindrical form and spindle axis and anvil axis is made perpendicular.
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