# Micrometer screw – problems and solutions

Micrometer screw – problems and solutions

1. The measurement of the diameter of the wire with a micrometer is 2.48 mm. The image corresponding to the measurement result is…

Solution :

A. Wire diameter = 4, …..

B. Wire diameter = 3, …..

C. Wire diameter = 2, …..

D. Diameter of wire = 1, …..

E. Wire diameter = 4, …..

2. The measurement of the diameter of the wire with a micrometer is 1.95 mm. The image that matches with the measurement results is…

Solution :

A.

Main scale = 1.5 mm

Swivel scale = 38 x 0.01 mm = 0.38 mm

0.01 mm is the threshold of micrometer screws accuracy.

Wire diameter = 1.5 mm + 0.38 mm = 1.88 mm.

B.

Main scale = 1.5 mm

Swivel scale = 39 x 0.01 mm = 0.39 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 1.5 mm + 0.39 mm = 1.89 mm

C.

Main scale = 1.5 mm

Swivel scale = 43 x 0.01 mm = 0.43 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 1.5 mm + 0.43 mm = 1.93 mm

D.

Main scale = 1.5 mm

Swivel scale = 42 x 0.01 mm = 0.42 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 1.5 mm + 0.42 mm = 1.92 mm

E.

Main scale = 1.5 mm

Swivel scale = 45 x 0.01 mm = 0.45 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 1.5 mm + 0.45 mm = 1.95 mm

3. The result of the measurement of the diameter of the metal granule sphere by using screw micrometer is 2.75 mm. The image that matches with the measurement results is…

Solution :

A.

Main scale = 2.5 mm

Swivel scale = 20 x 0.01 mm = 0.20 mm

Wire diameter = 2.5 mm + 0.20 mm = 2.7 mm

B.

Main scale = 2.5 mm

Swivel scale = 15 x 0.01 mm = 0.15 mm

Wire diameter = 2.5 mm + 0.15 mm = 2.65 mm

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C.

Main scale = 2.5 mm

Swivel scale = 25 x 0.01 mm = 0.25 mm

Wire diameter = 2.5 mm + 0.25 mm = 2.75 mm

4. The measurement of the diameter of the steel cylinder with a screw micrometer is 4.47 mm. The correct measurement result shown in the following figure is…

Solution :

A.

Main scale = 4.5 mm

Swivel scale = 47 x 0.01 mm = 0.47 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 4.5 mm + 0.47 mm = 4.97 mm

B.

Main scale = 4 mm

Swivel scale = 47 x 0.01 mm = 0.47 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 4 mm + 0.47 mm = 4.47 mm

C.

Main scale = 5.5 mm

Swivel scale = 47 x 0.01 mm = 0.47 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 5.5 mm + 0.47 mm = 5.97 mm

D.

Main scale = 3 mm

Swivel scale = 47 x 0.01 mm = 0.47 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 3 mm + 0.47 mm = 3.47 mm

E.

Main scale = 7.5 mm

Swivel scale = 47 x 0.01 mm = 0.47 mm

0.01 mm is the threshold of micrometer screws accuracy

Wire diameter = 7.5 mm + 0.47 mm = 7.97 mm

1. Question: What is the primary purpose of a micrometer screw?

Answer: The primary purpose of a micrometer screw is to measure small dimensions with high precision, typically to the nearest hundredth of a millimeter or thousandth of an inch.

2. Question: How does a micrometer achieve its precision?

Answer: A micrometer achieves its precision through a finely threaded screw mechanism. One complete turn of the thimble advances or retracts the spindle by a known small distance.

3. Question: What is the ‘pitch’ of the micrometer screw?

Answer: The pitch is the linear distance the spindle moves for one complete rotation of the screw.

4. Question: Why do micrometers have a ratchet mechanism?

Answer: The ratchet mechanism ensures consistent force when tightening the micrometer, preventing over-tightening and potential damage to the object being measured or the micrometer itself.

5. Question: How is the reading on a micrometer taken?

Answer: The reading is taken by combining the linear measurement indicated on the sleeve with the rotational measurement from the thimble scale.

6. Question: Why is the frame of a micrometer often ‘C’ shaped?

Answer: The ‘C’ shape provides strength and rigidity to the instrument while allowing easy access for placing and removing the object being measured.

7. Question: What are the anvil and spindle in the context of a micrometer?

Answer: The anvil is the stationary part against which the object is placed, and the spindle is the moving part that contacts the other side of the object being measured.

8. Question: What precaution should be taken when storing a micrometer?

Answer: A micrometer should be stored with the spindle slightly away from the anvil, preventing the pressure of constant contact and potential deformation. Also, storing it in a protective case prevents dust accumulation and physical damage.

9. Question: Why is it important not to drop a micrometer?

Answer: Dropping can damage the precision surfaces of the anvil and spindle, compromise the alignment, and adversely affect its accuracy.

10. Question: How does temperature affect micrometer measurements?

Answer: Metals expand with an increase in temperature. Since micrometers are often made of metal, temperature changes can affect their dimensions and, thus, the accuracy of measurements.

11. Question: What is the function of the lock on some micrometers?

Answer: The lock, or locking mechanism, secures the spindle in place after a measurement is taken, ensuring it doesn’t move while reading the measurement.

12. Question: Why do some micrometers have a carbide-tipped anvil and spindle?

Answer: Carbide tips are harder and more wear-resistant than plain steel, ensuring longer life and consistent accuracy of measurements.

13. Question: What is the difference between a micrometer and a caliper?

Answer: While both are measuring tools, a micrometer measures using a screw mechanism and is generally more precise. In contrast, a caliper uses a slide mechanism and can measure internal, external, and depth dimensions.

14. Question: How is zero error accounted for in a micrometer?

Answer: Zero error is checked by closing the micrometer without any object between the anvil and spindle. Any discrepancy from zero is noted and adjusted for in subsequent measurements.

15. Question: Why should one avoid rotating the thimble rapidly?

Answer: Rapid rotation can damage the threads of the micrometer screw, affecting its accuracy.

16. Question: Why are digital micrometers considered advantageous by some users?

Answer: Digital micrometers provide direct digital readings, eliminating potential reading errors from the analog scale, and can be quicker and more intuitive for some users.

17. Question: What is the function of the scale on the sleeve of the micrometer?

Answer: The scale on the sleeve indicates whole millimeters or tenths of inches (depending on the unit) and provides the main linear measurement.

18. Question: Why is the thimble typically divided into 50 or 100 divisions?

Answer: This division corresponds to the pitch of the screw. For a 0.5 mm pitch, each division on the thimble represents 0.01 mm. For a 0.025-inch pitch, each division would indicate 0.0005 inches.

19. Question: How can a user measure the depth using a micrometer?

Answer: Depth measurements typically require a depth micrometer, which has a rod extending from the base for depth measurement, as opposed to the typical outside micrometer.

20. Question: What’s the significance of having a friction thimble on some micrometers?

Answer: A friction thimble ensures that a consistent force is applied when taking measurements, leading to more consistent and accurate readings.

Understanding the intricacies of the micrometer screw is vital for those in precision engineering and related fields where accurate measurements are essential.