# Screw Gauge: Parts, Working, and How to Take Reading

What is Screw Gauge?

Screw Gauge is a mechanical tool that is used to measure the diameter or radius or thickness of a thin metal sheet with utmost precision. There are two scales known as Pitch Scale which is generally the main scale and also is engraved on the barrel with upright lines.

Another one is the Circular scale which is engraved horizontally on the thimble. The pitch range determines the range in millimeters (mm) traveled by the spindle per transformation. One change by the round range amounts to fifty percent of a millimeter of displacement of the screw is called a micrometer screw gauge.

The readings of screw gauge are more precise and accurate as compared to Vernier Calipers.

##### Parts of Screw Gauge

It includes a U-shaped steel structure F with a fixed stud A.

• The right moveable R (called Ratchet) is a cylinder kind whose other end is called the spindle.
• A static straight scale or the main scale (usually in mm) is noted on a cylindrical tube.
• The second scale (moveable) is called a circular scale or a capped range (with 50 or 100 parts) which is made use of a cap called thimble ‘T’ fitted over a cylindrical tube.
• The round scale is made as though one total turning of the cap relocate horizontally by 1 mm on the main scale if circular scale cap relocates horizontally by 1 mm on the major scale if circular scale division is 100 and also 0.5 mm in the main scale if the circular scale division is 50.
##### Working of Screw Gauge

The primary step is to locate the zero error of the screw gauge.

##### Zero Error

To find the zero error, shut the void between the pin and the stud of the screw gauge by rotating the ratchet in the clockwise direction. If the zero of circular range coincides with the index line, then the zero error will certainly be zero.

Zero error will be positive if zero of the circular scale is behind the index line. In this instance, multiply the number of divisions of the circular scale that has not crossed the index line with the least count of screw gauge to fine zero error.

Zero error will certainly be negative if zero of circular scale has crossed the index line. In this situation, increase the number of divisions of the circular scale that has crossed the index line with the least count of screw scale to find the zero error.

The size of a provided object can be found as follows:

1. Shut the space in between the spindle and the stud of the screw gauge by turning the ratchet in the clockwise direction.
2. Note the main scale along with circular scale reading to locate zero error as well as for this reason no modification of the screw gauge.
• Open the void in between stud and pin of the screw scale by turning the ratchet in the anti-clockwise direction. Place the object in the void. Turn the ratchet to ensure that the object is pressed carefully between the studs and also the spindle.
1. Note main scale as well as circular scale readings to find the size of the object.
2. Apply zero error to get the correct diameter of the object.
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Least Count of Screw Gauge

The least count of a screw gauge can also be found by the formula:

The least count of screw gauges is 0.01mm or 0.001cm.

### MCQs:

• What is Screw Gauge primarily used for?
• A) Measuring temperature
• B) Measuring length
• C) Measuring the diameter or thickness of a thin metal sheet
• D) Measuring volume
• Answer: C) Measuring the diameter or thickness of a thin metal sheet
• Which scale on the Screw Gauge determines the range traveled by the spindle per transformation?
• A) Main scale
• B) Circular scale
• C) Pitch scale
• D) Vernier scale
• Which part of the Screw Gauge includes a U-shaped steel structure with a fixed stud?
• A) Ratchet
• B) Thimble
• C) Circular scale
• D) Frame
• What is used to find the zero error of a Screw Gauge?
• A) Ratchet
• B) Main scale
• C) Circular scale
• D) Stud
• How is the zero error determined if the zero of the circular scale coincides with the index line?
• A) It is positive
• B) It is negative
• C) It is zero
• D) It is not determined
• Answer: C) It is zero
• What is the main step to take before measuring an object with a Screw Gauge?
• A) Finding the least count
• B) Finding the zero error
• C) Closing the gap between spindle and stud
• D) Opening the gap between spindle and stud
• Answer: B) Finding the zero error
• What is the least count of a screw gauge?
• A) 0.1 mm
• B) 0.01 mm
• C) 1 mm
• D) 0.001 mm
• What is the function of the circular scale on a Screw Gauge?
• A) Determining the least count
• B) Closing the gap between spindle and stud
• C) Measuring the range traveled by the spindle
• D) Providing additional precision in measurements
• What happens if the zero of the circular scale is behind the index line?
• A) Zero error is positive
• B) Zero error is negative
• C) Zero error is zero
• D) Zero error is not determined
• Answer: A) Zero error is positive
• How is the length of an object measured using a Screw Gauge?
• A) By opening the gap between spindle and stud
• B) By closing the gap between spindle and stud
• C) By noting down the main scale reading
• D) By rotating the ratchet clockwise
• Answer: A) By opening the gap between spindle and stud
• Which part of the Screw Gauge determines the size of the object being measured?
• A) Circular scale
• B) Thimble
• C) Stud
• D) Ratchet
• What is the least count of screw gauges typically?
• A) 0.1 mm
• B) 0.01 mm
• C) 1 mm
• D) 0.001 mm
• How is the zero error corrected in Screw Gauge readings?
• B) By subtracting it from the actual reading
• D) By turning the ratchet anti-clockwise
• Which scale is engraved horizontally on the thimble in Screw Gauge?
• A) Pitch scale
• B) Circular scale
• C) Main scale
• D) Vernier scale
• What part of Screw Gauge determines the displacement of the screw when the cap is turned?
• A) Frame
• B) Circular scale
• C) Thimble
• D) Main scale
• What is the function of the ratchet in a Screw Gauge?
• A) To provide additional grip
• B) To adjust the circular scale
• C) To open and close the gap between spindle and stud
• D) To adjust the main scale
• Answer: C) To open and close the gap between spindle and stud
• What is the purpose of finding the zero error in Screw Gauge?
• A) To ensure accuracy in measurements
• B) To determine the least count
• D) To calibrate the instrument
• Answer: A) To ensure accuracy in measurements

1. What is Screw Gauge used for?
• Screw Gauge is used to measure the diameter, radius, or thickness of thin metal sheets with precision.
2. What are the main parts of a Screw Gauge?
• The main parts include a U-shaped steel structure with a fixed stud, a movable ratchet, a spindle, a main scale, and a circular scale.
3. How does a Screw Gauge work?
• Screw Gauge works by adjusting the gap between the spindle and the stud to accommodate the object being measured, then reading the main and circular scales to determine its size.
4. What is Zero Error in Screw Gauge?
• Zero Error refers to the discrepancy between the actual zero point on the circular scale and the reference index line. It can be positive, negative, or zero.
5. How do you find the Zero Error of a Screw Gauge?
• The Zero Error is found by aligning the zero of the circular scale with the index line. If it doesn’t align, the number of divisions offset is multiplied by the least count to determine the error.
6. How do you take a reading with a Screw Gauge?
• To take a reading, close the gap between the spindle and the stud, note the main and circular scale readings, insert the object, then open the gap and note the readings again to calculate the size.
7. What is the Least Count of Screw Gauge?
• The Least Count is the smallest measurement that can be read from the screw gauge. It is typically 0.01 mm or 0.001 cm.
8. How is the Least Count of Screw Gauge determined?
• The Least Count is determined using the formula specific to the screw gauge being used, based on the pitch and the number of divisions on the circular scale.
9. What is the significance of the Circular Scale on a Screw Gauge?
• The Circular Scale provides additional precision in measurements, allowing for more accurate readings.
10. Are readings from Screw Gauge more accurate than those from Vernier Calipers?
• Yes, the readings from Screw Gauge are generally considered to be more precise and accurate compared to Vernier Calipers.
11. Can Screw Gauge be used to measure lengths other than diameter or thickness?
• While Screw Gauge is primarily used for measuring diameters or thicknesses, it can potentially be adapted for other length measurements with suitable modifications.
12. What should be done if the Zero Error of a Screw Gauge is determined to be positive?
• If the Zero Error is positive, it should be added to the measured value to obtain the correct reading.
13. Is it necessary to find the Zero Error every time before using Screw Gauge?
• Yes, it is crucial to find and account for the Zero Error before taking measurements to ensure accuracy in readings.
14. Can Screw Gauge be used for measuring non-metallic objects?
• Screw Gauge is primarily designed for measuring metallic objects, but with appropriate adjustments, it may be possible to use it for non-metallic objects as well.
15. What precautions should be taken while using Screw Gauge?
• Precautions include handling the instrument delicately, ensuring proper alignment, and avoiding excessive force while taking measurements to prevent damage and inaccuracies.