In projects where accurate measurement must prevail, a vernier caliper must come into use. Because a caliper measures 95% of lathe operations, the lathe machinist can relate to it better. This is to say, it is a special tool for lathe operators.
A Vernier Caliper is a precision measuring instrument used to measure the internal and external dimensions of an object. Its two major parts include a fixed jaw and a movable jaw.
The fixed jaw measures the outside, and the movable jaw measures the inside. Vernier calipers can measure smaller values from about 0.1 mm. Vernier calipers are used in different fields and applications, including science, construction, engineering, and manufacturing. They are used for the same purpose, which is to take measurements.
Well, in this reading, we’ll explore what a vernier caliper is, its diagram, parts, and how to read it.
Let’s begin!
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What is a Vernier Caliper?
The vernier caliper, also referred to as the vernier scale, serves as a precise measuring tool for linear dimensions. In other words, it measures a straight line between two points. It can also measure the depth of a hollow part and the size of round objects. In other words, you can use a vernier caliper to measure depth, width, and linear parts.
You can also use it as a visual aid to accurately measure the distance between two graduation markings on a linear scale. This is achieved by enhancing resolution and minimizing measurement uncertainty through the use of vernier acuity, which reduces human estimation error.
The vernier caliper or scale was invented in 1631 by French mathematician Pierre Vernier. When used properly, its part works in tandem with the main scale to provide precise measurements.
An engineer’s toolbox must contain these useful tools. It contains a fixed main scale and a moving vernier scale. This main scale is labeled in millimeters or tenths of an inch. The precise measurement of a vernier caliper is due to its ability to take a reading, typically 0.02mm or 0.001 inch.
The resolution of a vernier caliper is the smallest distance that the caliper can measure. The resolution of imperial vernier calipers is usually 0.001 in, whereas the resolution of metric calipers is either 0.05mm or 0.02mm. The end part of the vernier scale typically indicates the caliper’s resolution.
Digital Vernier Calliper
The advancement of technology helped with the development of the Digital Vernier caliper. These digital calipers offer very accurate measurements, even more than the traditional ones. But it is a little pricier; maybe that’s why users prefer traditional calipers.
The digital vernier caliper takes measurements with a series of capacitance sensors that move around the beam length. The sensor will detect a change in the electrical charge when a change occurs in the distance of the jaws.
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Vernier Caliper Parts
The various parts of a vernier caliper are the main scale, vernier scale, fixed jaw, moveable jaw, zero adjustment screw, locking screw, lower jaws, upper jaws, depth screw, thumbscrew, lock screw, and lock screw.
- Main Scale: this scale is used to measure the overall length of an object.
- Vernier scale: it is used to measure small increments of an object’s length.
- Fixed jaw: is a stationary jaw used to measure the outside of an object.
- Movable jaw: is a moving jaw is used to measure the inside of an object.
- Zero adjustable screw: is used to make sure the vernier caliper is at zero before taking any measurement.
- Locking Screw: is used to ensure the movable jaw is in place after taking a measurement.
- Lower jaw: is used and designed to secure grip and measure the outer dimensions like diameter, width, and length.
- Upper jaw: is used for measuring inner dimensions. They are open to touching the edges of objects like hollow pipes and jars for accurate readings.
- Depth screw: is used to measure jar depth with the depth rod at the end of the main scale.
- Thumb screw: is used to ensure a secure grip for easy sliding of the jaws.
- Lock screw: is used to secure the jaw in place when the object is firmly held, to facilitate accurate reading.
Diagram of a Vernier Caliper
How to Use and Read a Vernier Caliper?
To use a vernier caliper, ensure the instrument is properly zeroed, which is done by loosening the locking screw and adjusting the movable jaw to reach the zero mark on the vernier scale to align with the zero on the main scale. Next, position the object for measurement between the fixed and movable jaws. tighten the locking screw to secure the movable jaw in place.
The main scale will give you the overall length of the object when you read the measurement from both the main scale and the vernier scale. The vernier scale gives small increments of length.
To ensure and verify an accurate measurement on a vernier caliper, you must make sure the main and vernier scales are aligned and there is nothing in between. Zero errors are eliminated when both scales read 0.
Place a ball between the scale jaws, aligning the 0 mark on the vernier scale with the main scale to get the main scale reading. Determine the point on the vernier scale that aligns with the main scale to obtain the vernier scale reading. These readings involve decimals, which occur after the main number and represent the vernier scale reading.
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Measuring Range and Tolerance of a Vernier Caliper
A vernier caliper measurement range is the difference between the largest and smallest value that a caliper can measure. The caliper range is sometimes called the maximum capacity of a caliper, which is equal to the length of the main scale. Most vernier calipers have a range of 6 inches (300mm). However, calipers are available in smaller and larger ranges.
Discussing tolerance or instrument error vernier calipers are good at that, the same as micrometers. They are tools purposely designed for low-tolerance measurement. Low-tolerance measuring tools are known for their very accurate measurements.
As for vernier calipers, their instrument error is mostly +- 0.03mm (+- 0.0015 in). As you see, that is quite tolerated, with the capability of measuring outside dimensions, inside dimensions, and depth. Some calipers that incorporate the Quadri feature are used to take step measurements.
Least Count of a Vernier Calliper
The least count of a vernier caliper is the smallest measurement the instrument can make. You can calculate it by dividing the smallest division on the main scale by the number of divisions on the vernier scale. The mathematical formula for the Least Count of Vernier Calliper is,
VC = 1 MSD – 1 VSD
Vernier Acuity and Zero Error
Vernier calipers are a popular tool due to their ability to detect alignment and misalignment, which surpasses the optical capability of the eye. This hyperacuity, which has not been exploited by other technologies, gives the vernier scale an advantage over its competitors.
Zero error, a condition where a measuring instrument registers a reading when there should not be one, occurs when a zero on the main scale does not coincide with a zero on the vernier scale. This error can be positive or negative. To use a vernier scale with zero error, use the formula: Actual reading = main scale + vernier scale – (zero error).
However, zero error may arise due to knocks or damage, causing misaligned 0.00 mm marks when the jaws are perfectly closed or touching each other.
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FAQs
What is a Vernier Caliper?
Vernier Calliper is a precision measuring instrument used to measure the internal and external dimensions of an object. Its two major parts include a fixed jaw and a movable jaw.
How does a Vernier Caliper Work?
A vernier Calliper works on the principle of Vernier scale, which provides accurate measurement readings. The main scale measures whole units, while the vernier scale slides along the main scale and provides additional fractional readings.
What are Parts of a Vernier Caliper?
The parts of a vernier caliper are the main scale, vernier scale, jaws for measuring outer dimensions, and depth gauge for measuring depths. It also includes a locking screw to hold measurements in place.
How to Read Measurements on a Vernier Caliper?
To read measurements on a vernier Caliper, align the object between the jaws and read the main scale reading at the zero mark of the vernier scale. Then, identify the graduation line on the vernier scale that perfectly aligns with a graduation line on the main scale. The value indicated by the aligned lines on the vernier scale represents the fractional part of the measurement.
What are Applications of Vernier Calipers?
Calipers are used in various fields, including engineering, manufacturing, and science, where precise measurements are required. They are commonly used for measuring dimensions of objects, thickness, inner and outer diameters, as well as depth measurements.