Screw Gauge - Definition, Formula, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:35 PM IST

What is a Screw gauge?

A screw gauge is a tool that usually makes it easy to measure the width or radius or the thickness of a thin wire or even the thickness of a thin metal wire with great accuracy.
This tool consists mainly of a U-shaped frame and a nail (or screw) attached to a thimble. There are usually two scales known as the Pitch of screw gauge Scale which is a large scale and is written on a barrel with vertical lines. The other is a circular circle inscribed horizontally on the thigh. Pitch of screw gauge scale measures the distance in millimeters (mm) propelled by a spindle for each change. Another change in a circular motion equal to half a millimeter of screw transfer is called a micrometer screw gauge. Micrometer scales are very accurate and accurate compared to the Vernier Caliper scale.

Screw Gauge - Definition, Formula, FAQs

Before you start measuring, it is important to make sure that the 'Stud-end' and 'Spindle (or Screw) end' areas are cleaned; otherwise the measurements obtained will provide the wrong size.

‘Anvil’ is motionless and attached to the U-shaped frame. When the anvil and the spinning tin (or screw) are touched, the Pitch of the screw gauge Scale zero (or large zero scale) must correspond to the zero of the circular scale. This is considered a reference.

screw gauge

As the anvil is repaired, therefore, it is appropriate to place the object, its size to be measured, firmly near the temple. At the same time, a circular thimble at one end of the gauge needs clockwise rotation. This action will cause the spinning section (or screw) to move forward in the direction of the anvil. Continue to rotate the scepter so that the spindle (or screw) reaches the object, which is placed near the temple.

In the latter case, the object, the size of which is available, must be held firmly and firmly between the temple and the tile. A three-click Ratchet is used as long as a direct spinning operation is performed. This position can be locked using the lock key located next to the spinning wheel.

Once the previous step is detected, the pitch of screw gauge scale and the circular scale should be read. The pitch of screw gauge scale reading is the significance of the Pitch of screw gauge scale when it touches the sleeve of a circular scale. Round scale reading is a line-based reading on a pitch of screw gauge scale. A magnifying glass can be used to read measurements. Suppose a reading of a field is 'X' and a circular reading is a 'Y'.

The final calculation will be as follows:

Total reading = X (mm) + (Y x LC gauge) mm

Here, LC is a very small number of gauges.

Also read -

Screw gauge measurement using Inch Micrometer. Define gauge.

The value of the pitch of screw gauge scale is calculated in half an inch. The number 5 (or graduation 5) in the barrel means half an inch or 0.500 inches. There are 4 stages between graduation 0 and graduation 1 on the pitch of screw gauge scale. Therefore, the first graduation seen in the bin as number 1 is actually the 10th inch or 0.100 inches or 100th of 1000 inches. Similarly, 2 graduates are 0.200 inches or 200th of 1000 inches or 20 200 inches. So the smallest separation on the pitch of screw gauge scale can be 0.025 inches or 25th of 1000 inches.

Screw gauge formula: micrometer least count formula

Pitch of screw gauge scale measures the distance in millimeters (mm) that the spindle moves by each turn. The volume of the screw pitch gauge scale is calculated as given below:

Pitch of screw gauge of the Screw gauge = The distance traveled by the screw Rotation value

To measure the size of a small wire or a small sheet using a screw gauge, one needs to know a small calculation. The minimum screw pitch gauge calculation can be calculated using the formula given below:

Small screw gauge calculation = Screw Number Pitch of screw gauge for circular scale sections

Once the minimum number of gauges has been calculated, the final reading is calculated as below

Related Topics,

Complete Reading = High-Level Reading + Circular Circle reading x LC gauge.

The LC in the above equation is a small gauge calculation. There may be a chance that the zero of the pitch of screw gauge scale does not correspond to the zero of the circular scale. In that case, either the scale can be above or below the pitch of screw gauge scale (also known as the larger scale).

If the zero of the circular scale is less than the pitch of the screw gauge scale, it is known as the correct zero error. The value of the circular separation below the pitch of screw gauge scale should be multiplied by a small gauge count. This value should be deducted from the full study of the appropriate values. So the formula is as follows:

Complete Reading = Circular Scale Reading

If the zero of the circular scale exceeds the pitch of the screw gauge scale, it is known as a non-zero error. The value of the circular separation above the pitch of screw gauge scale should be multiplied by a small gauge count. This number will be included in the full study of the relevant estimates. So the formula is as follows:

Complete Reading = Circular Scale Reading

An example of how to read a screw gauge measure using a micrometer is discussed.

If a micrometer has a pitch of screw gauge of 0.5 mm. It means that with one complete rotation of the thimble scale, a distance of 0.5 mm travels through the thread. There are 50 sections on a circular scale. The minimum calculation will be 0.01 mm calculated as below.

Minimum number = Pitch of screw gauge Number = 0.550 = 0.01mm

Hence the pitch of screw gauge scale reading is 3 mm. According to a circular scale reading, 46 divisions are like a reference line on a pitch of screw gauge scale. So the full reading will be

Complete Reading = High-Level Reading + Circular Circle reading x LC gauge

= 3mm + 46 × 0.01 mm = 3.46 mm.

Also, check-

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NCERT Physics Notes:

Frequently Asked Questions (FAQs)

1. What is the least count of screw gauge calculation?

The formula for calculating the minimum screw gauge is as follows:

Minimum screw gauge = (Pitch of screw gauge of screw gauge) / (total number of stages)

Minimum calculation of micrometer screw gauge = (1 mm) / (100) = 0.01 mm.

2. What is the zero gauge screw error?

Zero Screw gauge Error:

When the surface of the screw plane and the plane of the plane different from the frame are touched, if the zero of the head scale meets the axis of the pitch of screw gauge scale, there is no zero error.

3. How do you fix screw problems?

Solution: The distance travelled by the line scale when the circular scale makes the full rotation p = 1mm p = 1 m m (tone). The value of a split on a circular scale is N = 100. Therefore, one partition on a circular scale is LC = p / N = 1/100 = 0.01mm LC = p / N = 1/100 = 0.01 m m.

4. What is the principal of the screw gauge?

The screw gauge works on the travel principle. When the screw is rotated, there is a direct movement on the large scale of the screw gauge. This scale is used to calculate the minimum length. The distance travelled by the rotating cable for each rotation is known as the pitch of screw gauge

5. What is the minimum calculation formula?

The smallest Vernier scale calculation is calculated using the following formula, Minimal calculation = Very small reading on the large scale Verseer scale scale Vernier = 1mm10 = This is the smallest number of Vernier Callipers. Therefore, the micrometer least count for Vernier Callipers is 0.1mm.

6. What are the two types of zero error?

There are two types of zero errors - wrong error and positive error

7. How many types of measuring screws?

The following are four common types of micrometer screw gauge and 3 types of special micrometer targets.

8. How does the principle of a screw gauge work?

The screw gauge works on the principle of a screw thread. As the screw is rotated, it advances or retreats by a fixed distance for each complete turn. This fixed distance is called the pitch of the screw. By counting the number of rotations and fractions of rotations, very small distances can be measured accurately. The main scale (sleeve) shows whole millimeters, while the circular scale (thimble) allows for reading fractions of a millimeter, typically to 0.01 mm precision.

9. What is the least count of a typical screw gauge?

The least count of a typical screw gauge is 0.01 mm (or 10 micrometers). This means it can measure dimensions to the nearest hundredth of a millimeter. The least count is determined by the pitch of the screw (usually 0.5 mm) divided by the number of divisions on the circular scale (usually 50). Some high-precision screw gauges may have a least count of 0.001 mm.

10. How does the pitch of a screw gauge affect its measurements?

The pitch of a screw gauge is the distance the spindle moves for one complete rotation of the thimble. It directly affects the precision of measurements. A smaller pitch allows for finer measurements. Most screw gauges have a pitch of 0.5 mm, meaning the spindle advances 0.5 mm for each complete rotation. The pitch, combined with the number of divisions on the thimble, determines the least count of the instrument.

11. How do you read a screw gauge?

To read a screw gauge:

12. What is zero error in a screw gauge and how does it affect measurements?

Zero error in a screw gauge is the deviation from zero when the spindle is in contact with the anvil. It can be positive (if the zero on the thimble scale is above the reference line) or negative (if it's below). Zero error affects all measurements and must be accounted for by adding it to (for negative error) or subtracting it from (for positive error) each reading to get the true value. Regular calibration helps minimize zero error.

13. What is a screw gauge and why is it used in physics?

A screw gauge, also known as a micrometer screw gauge, is a precision measuring instrument used in physics to measure small distances or thicknesses with high accuracy. It is particularly useful for measuring the diameter of thin wires, the thickness of sheets, or small objects with dimensions typically in the range of 0 to 25 mm. The screw gauge is preferred in physics experiments because it can measure to an accuracy of 0.01 mm or even 0.001 mm, making it ideal for precise measurements in various scientific applications.

14. How does the ratchet mechanism in a screw gauge ensure consistent measurements?

The ratchet mechanism in a screw gauge ensures that a consistent and appropriate amount of pressure is applied when taking measurements. It prevents over-tightening of the spindle, which could damage the object being measured or the instrument itself. When the correct pressure is reached, the ratchet slips, making a clicking sound. This mechanism helps eliminate variations in measurements due to different users applying different amounts of pressure, thus improving the consistency and reliability of readings.

15. Can a screw gauge be used to measure soft or compressible materials?

While a screw gauge is primarily designed for measuring rigid materials, it can be used for soft or compressible materials with caution. However, measurements of soft materials may be less accurate due to compression. When measuring soft materials:

16. What is backlash error in a screw gauge and how can it be minimized?

Backlash error in a screw gauge occurs when there's a slight play or looseness in the screw mechanism. This can cause inconsistencies in readings, especially when changing the direction of rotation. To minimize backlash error:

17. How does parallax error affect screw gauge readings and how can it be minimized?

Parallax error occurs when the observer's line of sight is not perpendicular to the scale being read, leading to incorrect readings. In a screw gauge, this can happen when reading both the sleeve and thimble scales. To minimize parallax error:

18. What are the main parts of a screw gauge?

The main parts of a screw gauge include:

19. Why is temperature control important when using a screw gauge?

Temperature control is crucial when using a screw gauge because thermal expansion or contraction can affect both the instrument and the object being measured. Changes in temperature can cause the metal components of the screw gauge to expand or contract, potentially leading to inaccurate readings. Similarly, the object being measured may change size with temperature fluctuations. For high-precision measurements, it's important to ensure both the screw gauge and the object are at a stable, known temperature, typically room temperature (20°C or 68°F).

20. How does the material of the screw gauge affect its performance?

The material of the screw gauge significantly affects its performance:

21. How does the frame design of a screw gauge affect its measurements?

The frame design of a screw gauge is crucial for accurate measurements:

22. What is the importance of the locking mechanism in a screw gauge?

The locking mechanism in a screw gauge serves several important functions:

23. How do you determine if a screw gauge has a positive or negative zero error?

To determine the type of zero error:

24. What is the difference between accuracy and precision in screw gauge measurements?

Accuracy refers to how close a measurement is to the true value, while precision refers to the consistency or reproducibility of measurements. A screw gauge can be precise (giving consistent readings) without being accurate (if it has a zero error, for example). Accuracy is about correctness, while precision is about repeatability. An ideal screw gauge should be both accurate and precise, giving consistent readings that are close to the true value of the dimension being measured.

25. How does the concept of significant figures apply to screw gauge measurements?

Significant figures in screw gauge measurements reflect the precision of the instrument and the confidence in the measurement. For a typical screw gauge with a least count of 0.01 mm:

26. What is the relationship between the pitch of the screw and the number of divisions on the thimble?

The relationship between the pitch of the screw and the number of divisions on the thimble determines the least count of the screw gauge. The formula is:

27. Can a screw gauge be used to measure internal diameters?

Standard screw gauges are designed to measure external dimensions and are not suitable for measuring internal diameters. However, there are specialized versions called internal micrometers or bore gauges that can measure internal diameters. These tools work on similar principles but have a different configuration to access internal spaces. For precise internal measurements, it's important to use the appropriate tool rather than trying to adapt a standard external screw gauge.

28. How does wear and tear affect the accuracy of a screw gauge over time?

Wear and tear can significantly affect the accuracy of a screw gauge over time:

29. How does the principle of vernier scale apply to a screw gauge?

While a screw gauge doesn't use a vernier scale directly, it applies a similar principle of subdividing measurements for greater precision. In a screw gauge:

30. How does the screw gauge compare to other precision measuring instruments like vernier calipers?

Screw gauges and vernier calipers are both precision measuring instruments, but they have distinct characteristics:

31. What role does friction play in screw gauge measurements, and how is it managed?

Friction plays a crucial role in screw gauge measurements:

32. How does the circular scale on the thimble of a screw gauge enhance measurement precision?

The circular scale on the thimble of a screw gauge significantly enhances measurement precision:

33. What are the limitations of a screw gauge in measuring very thin objects?

While screw gauges are precise instruments, they have limitations when measuring very thin objects:

34. How does the concept of mechanical advantage apply to a screw gauge?

The concept of mechanical advantage in a screw gauge relates to how a small rotation of the thimble translates into a very small linear movement of the spindle: