When listing precision measuring instruments, for sure, a micrometer screw gauge must be among them. It is one of the older precision measuring tools capable of measuring smaller dimensions vernier calipers cannot measure. Macrometer screw gauges are precision instruments purposely designed for taking small measurements with high accuracy. They are often used in metalworking, mechanical engineering, and laboratory settings.
These precision tools are used to measure the dimensions of objects with precision up to the hundredths of a millimeter (0.01 mm). They can also measure thousandths of an inch (0.001 inch). Well, in this reading, we’ll explore what a micrometer is, its parts, diagram, types, how it works, and how to read.
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What is a Micrometer Screw Gauge?
A micrometer screw gauge is a device widely used in the mechanical engineering field for measuring extremely small dimensions. Though it belongs to the family of calipers and also consists of two different scales. Hand tools are used in telescopes or microscopes to measure the potential diameter of microscopic objects.
Micrometers are not always in the form of calipers, but their spindle is a very accurately machined screw. The part to be measured will be placed between the spindle and the anvil. This spindle moves toward the object to be measured when the ratchet knob is turned and the object is lightly touched against the anvil.
In the 17th century, William Gascoigne invented the first micrometric screw as an improvement of the vernier. it was used in a telescope to measure angular distances between stars and the relative sizes of celestial objects. A micrometer is a neoclassical coinage word from Greek, micros meaning ‘small’ and metron meaning ‘measure’. It has been micrometer Merriam-Webster that English got it from French.
In the early 19th century, Henry Maudslay developed a bench micrometer. He was given jocularly nicknamed “the Lord Chancellor” among his staff because of the micrometer final judge on measurement accuracy and micrometer in the firm’s work. In 1844, details of Whit’s worth includes published.
Related: What is Vernier Caliper? its Diagram & How to Read
Micrometer Parts
The various parts of a micrometer screw gauge are frame, anvil, spindle, sleeve, thimble, ratchet, screw, and lock.
- Frame: this is the c-shaped body of the instrument. It holds and supports the anvil and the barrel.
- Anvil: this part put the measuring surface in fixed position against the object to be measured is placed
- Spindle: is the part that moves parallel to the anvil when the thimble is rotated, allowing for the measurement of objects.
- Sleeve (or Barrel): is a stationary cylindrical component marked with a scale in millimeters or inches, providing the main unit measurements.
- Thimble: is the rotating part that fits over the sleeve, marked with a circular scale that provides further precision to the measurement.
- Ratchet Stop: A mechanism used to apply a consistent measuring force to ensure repeatable and accurate measurements.
- Lock Nut: A feature used to lock the spindle in place once a measurement has been taken, allowing for easy reading without the risk of altering the setting.
Diagram Micrometer Screw Gauge
How Does Micrometer Works?
Micrometers utilize screws to convert small distances into large rotations of the screw, which can be read from a scale. The accuracy of a micrometer is based on the thread-forms, which can be a differential screw. The screw’s lead is a constant that correlates the amount of rotation with axial movement, and vice versa. The lead is the distance the screw moves forward axially with one complete turn (360°).
An appropriate lead and major diameter of the screw amplify a given amount of axial movement in the resulting circumferential movement. For example, if the lead of a screw is 1 mm and the major diameter is 10 mm, the circumference of the screw is 10π, or about 31.4 mm. This amplification allows a small difference in the sizes of two similar measured objects to correlate to a larger difference in the position of a micrometer’s thimble.
In classic-style analog micrometers, the position of the thimble is read directly from scale markings on the thimble and sleeve. A vernier scale is often included, allowing the position to be read to a fraction of the smallest scale mark. Digital micrometers display the length digitally on an LCD, while mechanical-digit versions exist, like car odometers where numbers “roll over.”
Watch the video below to learn the working of a micrometer:
How to Read a Micrometer?
Before using micrometer tool for measurement, ensure it is English or metric and has the same unit of measure as your current tool. Rotate the micrometer into the correct measurement and add the numbers found on the spindle and thimble for accurate results.
The type and design of the micrometer determine how to find desired numbers, and manufacturer instructions on reading the micrometer are provided.
A micrometer is a tool used for precise measurement of various objects, including the size of pipes, tools, and hollow objects. It can measure the inside width of a pipe, bearing, or depth of a hole or recess.
Accuracy is crucial in machines with moving parts, as parts that move in and out of each other need to remain in a steady, straight line. Micrometers are also used in applications like bearings, pipe fittings, and sheet metals, where the thickness of items like sheet metals is crucial.
In essence, micrometers are the preferred tool for precise measurement in various applications, ensuring the safety and integrity of the object being measured.
Related: 16 Types of Measuring and Marking-out Tools and Their Uses
Things to Know While Using Micrometer
The first thing to know is to be familier with the instrument, take note of the moveable and the stationary parts. Before taking any measurement, ensure you clean the spindle and anvil. This should be done with a paper or a clean cloth.
When cleaning, place the cleaning material in the mist of the spindle and the anvil and tighten the setup slightly until the paper or cloth is jammed, then pull it out. This step help to take accurate measurement.
At this point you can take the measurement, which is done by placing the object between the spindle and anvil. The object should be placed against the anvil because it is stationary in nature. The object is expected to be placed properly so it does not shake while taking the measurements.
The ratchet counter is rotated in clockwise to tighten the spindle, ensure that the timble zero are parallel to the line of the scale on the sleeve. The spindle is tighten against the object and force should applied until the clickable thimble clicks three times.
Lock the thimble while the object when it is forcefully placed. The spindle is still movable even as then thimble is locked. This help to get a precise measurement.
The object’s measurement should taken cautiously as the screw gauge accuracy can be compromsied. Note the reading before you unlock the spindle, then re-measure the while setup to comfirm the measurement.