Screw micrometer – As we know, we can find many measuring devices from caliper, from
anemometer to screw micrometer. In this context, we will take a closer look at the definition,
history, functions, types and uses of a screw micrometer measuring instrument.
In general, the micrometer itself is a measuring instrument that performs almost the same function as a
caliper, namely to measure the length of an object. However, when viewed from the level of
accuracy between the two tools, the screw micrometer has a higher level of accuracy, which is 10 times more
accurate. To learn more about measuring screw micrometers, see the review below!
What is a Screw Micrometer?
A micrometer or commonly called a screw micrometer is a tool used to measure small/thin objects or plate-shaped
objects with fairly high accuracy.
The screw micrometer accuracy is 0.01 mm. This tool includes a widely used calibrated screw
that accurately measures components. Every day refrigerator and water pump repairmen use a
screw micrometer to measure the diameter of the copper wire used to replace damaged coils of wire.
Micrometers are also used in telescopes and microscopes, which measure the diameter of celestial bodies and
the diameter of microscopic objects, respectively. The micrometer used in telescopes was
invented by the English astronomer William Gascoigne around 1638.
Biological objects/targets examined with a microscope have dimensions/micron dimensions (μ).
For measurements (length, width, diameter) of a microscopic object an ocular micrometer is
The ocular micrometer has a flat round shape, in the middle of which there is a scale ‘resembling’ a ruler
numbered 0, 10, 20,…, 100. The ocular micrometer can be used by inserting it into the ocular lens.
The scale on the ocular micrometer can be determined by the unit length value using the objective
micrometer. This method is called calibration.
Measurements made with a micrometer include measuring cell size and diameter of the objective field of
view. The advantage or importance of micrometry is that the number of cells in each area can be
known or the concentration of cells in the sample can be determined in one sample. Using a
micrometer can help measure the internal structure the preparation is being made of.
The objective of the micrometer is in the form of a sliding glass with a scale like a ruler in the middle
without the number 100 units. The balance is sealed with a round cover glass. 100
units scale = 1 mm, so each unit corresponds to 0.01 mm or 10 µm, so the distance of each unit to the
objective micrometer looks different.
A micrometer is an instrument used in electrical engineering to measure the exact thickness of beams, bottom
outline and center, and rod slots.
History of Invention of the Screw Micrometer
The word micrometer comes from the neoclassical words for the Greek micros, meaning “small” , and metron,
meaning “measure”. The Merriam-Webster Collegiate
Dictionary says that the English micrometer was adopted by the French, with its
first known appearance in English in 1670.
And the measuring device, micrometer (μm) and micrometer (device/tool), as we know it today, was unknown.
However, people at that time had a strong desire and interest in the ability to measure small
objects. The word was no doubt born in connection with the venture.
The screw micrometer was first invented by William Gascoigne in the 17th century as a development of the
vernier scale; Used in telescopes to measure the angular distances between stars and the
relative sizes of celestial bodies.
In the early 1800s, Henry Maudslay invented the benchtop micrometer, which his partners jokingly called the “Lord
Chancellor” in reference to the device’s ability to determine the accuracy and precision of measurements in a
In 1844 details of Whitworth’s working micrometer were published. Described as having a strong
iron frame with two steel cylinders with superb finishing at opposite ends, joined by bolts.
The end of the cylinder where they meet is hemispherical. A screw is attached to the
wheel which can measure up to one thousandth of an inch.
The first documented development of the screw micrometer that is known to us is the caliper by Jean Laurent
Palmer of Paris in 1848; hence it is often said palmer in French, tornillo de Palmer (“Palmer
screw”) in Spanish, and kalibro Palmer (“Palmer’s term”) in Italian.
(This language is related to the word micrometer, meaning: micromètre, micrómetro, micrometro .) Micrometer
calipers were bought and sold en masse in the English-speaking countries by Brown & Sharpe in 1867,
sales rising until they were sold in every machine shop.
Brown & Sharpe was inspired by several previous devices, one of which was the Palmer design.
In 1888 Edward W. Morley improved the accuracy of morphometric measurements and demonstrated their
accuracy in complex experiments.
Pioneers of precision and accuracy in workshop tools and equipment, developed by tool pioneers such as
Gribeauval, Tousard, North, Hall, Whitney, and Colt. , Leland and others, with the development
of the Industrial Revolution era, the micrometer became an important part of the integration of applied
science and technology.
Since the beginning of the 20th century, it has been impossible to specialize in construction or machine tool
technology without knowledge of measurement technology, chemistry and physics (metallurgy, kinematics/dynamics
Screw Micrometer Function
In general, the function of this screw micrometer is widely used to measure the diameter or thickness of a
small object. As previously mentioned, this screw micrometer tool is more than 10 times more
accurate than a vernier caliper. So don’t be surprised if a micrometer can be used to measure
smaller objects or with an accuracy of 0.01 mm.
Using a micrometer to measure the length of objects is less common. Because the length of
objects can still be measured accurately with an accuracy of about 1mm and 0.1mm. This level of
accuracy belongs to the caliper.
Types of Micrometer Screws
Of the several functions, the screw micrometer consists of several types, namely:
Manual Screw Micrometer
It is one of the most commonly used types of screw micrometers. The price is cheaper than
other types. The scale consists of a main scale and a vernier scale. As the name
suggests, measurement readings are still done manually using the measurement instructions written on the
Digital Screw Micrometer
Unlike the manual version, the digital version of the micrometer has a digital display. You
can immediately see the measurement results on the screen without having to calculate them manually.
Maybe more expensive than the manual version. But the digital version makes it easier
to see the measurement results. This minimizes the risk of misreading or wrong
An outside micrometer is the type used to measure the outside diameter of the workpiece. This
type of micrometer is often used to measure objects such as wires, coatings, or blocks of material.
This is the type of micrometer commonly used to measure hole diameters. This micrometer can be
used to measure the diameter or diameter of the hole in an object. This type of micrometer is
also often used to measure the diameter of the depth of the tube.
This type of micrometer is most often used to measure the depth and height of an object. What
is the difference between internal micrometers? The difference is this type is used to measure
the depth of the hole. While the internal micrometer only measures the diameter.
Screw Micrometer Parts
The frame is the screw micrometer body, its function is as a frame for placing other micrometer components
and a holder for the micrometer. The micrometer body is made of cast steel resembling the
This makes the micrometer look strong and sturdy. This frame must not only be strong, but also
must be resistant to expansion. This is because as the frame expands, there is extra space
between the anvil and the spindle. The effect of natural measurement results is less accurate.
Therefore, the frame construction material is not only steel, but mixed with other materials to
make it more heat resistant.
Anvil / Fixed Shaft
The anvil is a small rod located at the end of the frame, the anvil is fixed, meaning this small anvil
cannot be moved. Anvil serves to hold the workpiece to be measured.
Spindle / Motion Shaft
The spindle is a longer rod that sits at one end of the frame. At first glance, the spindle
and anvil have a similar shape. However, the anvil is smaller and fixed while the axle is
longer and movable. The spindle functions to fix the workpiece to be measured, when the
workpiece is inserted into the micrometer, the object is fixed with the anvil and spindle.
The sleeve is a thimble, a tubular sleeve that sits on the outside of the micrometer frame.
The main function of the sleeve is actually a place to place the main scales.
The thimble is a metal rod in the shape of a tube that sits on the outside of the casing. The
function of the thimble is to set the vernier scale. The thimble can be rotated, and each turn
of the thimble moves the spindle.
Lock nut / lock
The lock nut or lock nut has a function to hold the spindle or axis of motion so that it does not move during the
process of measuring objects.
The ratchet rotates the spindle or axis of motion when the end of the spindle is near the object to be
measured. This section is then used to tighten the spindle or shaft by turning it clockwise
until it clicks. The ratchet is rotated 2-3 times to ensure that the spindle tip is in perfect contact with
the measuring object.
How to use a screw micrometer
Due to the mechanical advantage caused by the smooth thread of the screw, which moves the thimble and glue
to the right, the screw rotates easily and can accurately cover the measuring object. So that
the measurement object is more accurate and precise.
Generally, screw micrometers have two types of scales. The first scale is printed on the main
handle of the micrometer, which is a fixed scale. Another type of scale is the rotary scale,
which is contained in a rotary cylinder. Measurement results can be obtained by combining fixed
scale values and rotary scale values.
The method is as follows:
- Determine the fixed scale values bounded by the rotating scale. If not
the same, use the next smaller scale value. For example, a reading on a fixed scale limited
by a rotating scale is greater than 8 but not exactly 9. The measurement to be used is 8 mm.
- Find the number on the rotary scale that is parallel to the horizontal line on the
fixed scale. For example, line 43 of the rotary scale is parallel to the horizontal line of
the fixed scale. The magnitude of the measurement results obtained is 43 times the rotary
scale (43 x 0.01 = 0.43 mm).
- Add up the two measurements. We get the length of the object to be (8 +
0.43) mm = 8.43 mm.
How to Calibrate a Screw Micrometer
Because sometimes the accuracy of the screw micrometer changes after a few uses, the screw micrometer must
be calibrated to 0 so that the screw micrometer remains accurate when making measurements.
Below are instructions for calibrating a screw micrometer:
- Place and press the micrometer between the anvil and bobbin, pressing the micrometer by
turning the thimble sufficiently.
- If the micrometer adjuster bar is slightly pinched, pull the anvil and spindle back against
the adjuster by turning the ratchet until the spindle stops moving.
- If the difference between the 0 and the center line on the rotary scale does not exceed 0.02
mm, turn the sleeve with the adjustment key until the center line and the 0 line up with the 0 on the rotary
- If the difference between zero and the centerline of the scale is more than 0.02 mm, release
the snap button, hold down the sleeve and rotate the thimble with the adjust button until the dial scale
reads 0 on the centerline, scale , the screen will remain aligned when the snap handle is reattached.
How to Read a Screw Micrometer
The screw micrometer reading itself can be done in two ways or parts, namely the vernier scale and the main
scale. The main scale can be read on the micrometer screw arm and the vernier scale on the
thimble. For accurate measurement results, make sure the clamp of the object to be measured is
in the right or correct position. For more information on reading screw micrometer readings,
see the explanation:
- Note the position of the scale line at the top of the sleeve, which is 5mm
- See the scale line below, namely: 0.5 mm
- Then look at the vernier in the thumb area which is 28mm
- Multiply the vernier value by 28 x 0.01mm = 0.28mm
- Add up the results of the three measurements, namely: 5 mm + 0.5 mm + 0.28 mm = 5.78 mm.
- The final measurement result is 5.78 mm.
The difference between digital and analog
As you know, nowadays besides analog micrometers, there are also digital screw micrometers which are easier
to use. The most visible difference between analog and digital micrometers is in the reading of
the measurement results. On a digital micrometer, measurement results are easier to see.
In addition, this digital micrometer has the advantage of high accuracy, making it very suitable for
industrial use. But keep in mind that buying a screw micrometer should not be done haphazardly.
Before buying such a measuring device, there are a few things to consider. What are
the things to consider? Check out the review below:
- Remember to consider the micrometer measuring range of the screw.
- When purchasing a digital screw micrometer, be sure to pay attention to the data output
capability. In this case, you need to check how many ports you can connect to the
- Make sure the digital micrometer has read memory or not. In general,
whether a micrometer has memory or not can affect the price of the meter.
Note that analog and digital micrometers have very different prices. Usually the price of a
standard screw micrometer starts from one million. However, this price depends on the brand and
type of screw micrometer. The better the brand, the more expensive it is. So make
sure to buy a micrometer according to your needs.
Thus a review of the meaning, function, type, and how to use a screw micrometer that is good and right.
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Author: Ziaggi Fadhil Zahran