How to Calculate Screw Micrometer

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Micrometer Screw Is ? Here’s a guide on how to calculate a screw micrometer with examples of problems & how to calculate it

In the world of electronics, there are many variants of measuring instruments that are often used in research studies. One of the familiar measuring instruments is the Screw Micrometer.

Micrometer Screw Is?


A screw micrometer is a tool used to measure the dimensions of an object consisting of calibrated screws and has a precision level of 0.01 mm or equivalent to 10-5 m. Screw micrometers are used to measure the dimensions of a small object, such as diameter, length, and thickness.

This object was first used as a distance measure between angles on the star as well as other celestial bodies with the help of telescopes.

The first screw micrometer was invented in the 17th century by a person named Willaim Gascoigne. The existence of this tool as a solution is due to the need for a tool with a function that is much more precise than the caliper.

Although “micro” is attached to the name of this tool, it does not mean that this thing is used as a medium for measuring something microscale. The precision figure of the screw micrometer is 0.01 mm or the equivalent of 10-5 m.

Figures & Components of Screw Micrometers


The following is an example of a screw micrometer drawing along with parts of the micrometer. By observing the picture above, you can understand where each component is located in this measuring instrument.

  • Sleeve

It is in this section that one can see the scale of measurements that he is doing. The side is a static part and has a circle shape. In this tool, there are two types of scales, namely the nonius scale and the main scale. The unit of measure applied is in mm units.

On the sleeve there are numbers at the top starting from the number 1 while at the bottom it consists of numbers that include 0.5, 1.5, 3.5, and so on. Thus, the distance present on the two fruits of the smallest scale is 0.5 mm.

  • Thimble

The thimble becomes a component that serves as a drive. In order for this tool to move, it needs to be helped by the hands of someone who is using it.

Parts are made of metal that is rod-shaped. The size is larger when compared to the sleeve. In this section there are numbers that later show the measurement results.

The nonius scale present in the thimble section shows sizes 1 to 50, with a multiple of 5. If the thimble is rotated once in full, either backwards or forwards, then the main scale will decrease or increase by 0.5 mm. Thus, the distance between the two scales of the smallest is 0.01 mm.

  • Shear Shaft (Spindle Shaft)

This one part is a moving shaft which is a cylindrical component. When this tool is being used thimble will be a medium capable of causing the component to move. The movements are various such as moving away and approaching or retreating and advancing.

  • Fixed Shaft (Anvil)

Anvil is one of the parts of a screw micrometer which is an immovable shaft. In other words, this component is a part used for anchoring.

When measuring a certain object, the object is attached to the anvil. While on the side of the sliding shaft is positioned so that it is close and can clamp the object.

  • Lock Nut

So that the existing movement of the sliding shaft can be locked, then this part is very useful to help it. So when you are using this tool, make sure you understand the function of each part, including the lock nut.

  • Frame

This one component has a shape that resembles the letters C or U. This part serves to unite the fixed shaft part with other components on this measuring instrument. This one component made of a metal has the property of being able to withstand heat.

The frame is deliberately designed to be thicker than the other side. This aims to be sturdy and can keep the measured object from shifting or deforming, for example, long expansion. If this happens, it can disrupt the measurement process that is being carried out.

In addition, this frame also has a coating made of plastic. This layer is useful as a heat deterrent that propagates from the gauge to the metal during the measurement process.

  • Ratchet

Ratchet is a component that can help strive for the movement of the sliding shaft so that it can move more slowly when compared to moving the thimble. This component becomes the last part of the screw micrometer of the measuring instrument.

This part can also function as a sliding shaft fastener when it has hit the object. The way to tighten it is by rotating it clockwise.

Rotate it until you hear the sound of a metal knock (tick). In order to be able to ensure that the end of the shaft has been perfectly attached, the ratchet can be rotated 2 – 3 times.

Screw Micrometer Function


  • Measuring the Thickness of Small Objects

The first function of the screw micrometer is to measure the level of thickness and diameter of a certain object. This function is supported by a level of precision that reaches 10 × compared to the caliper.

Thus a screw micrometer can be used to measure objects that are smaller in size with an accuracy of 0.01 mm.

  • Measuring Diameter

This measuring instrument can also be used to measure the diameter of certain objects. However, it can only be measured in the outer diameter.

Some objects that can be measured in diameter using this tool are wires, bullets, cables, and other objects.

  • Measuring the Center Line

The next function is to measure the length of the midline of an object with holes. However, the objects that can be measured are only those that are small in size.

This is because this measuring instrument has a certain size limit. So that if you want to measure objects that can be bigger, you can use other types of measuring instruments.

  • Measuring Depth Levels

If you want to know the level of depth of an object, then this tool can be a medium that can be used. An example of an object measured using this tool is a pipe that is small in size.

Types of Screw Micrometers


There are several types of screw micrometers that you can use for measurement activities. The variants are divided into 2 types, namely based on scale and also based on function. For more details, please see below:

Based on Function:

  • Deep Micrometer

This measuring instrument is a type of media that is often used to measure the center line of an object or the diameter in a certain hole of an object. Thus, it can be concluded that the object measured using this tool is in the form of a circle or tube.

  • Outer Micrometer

This type of screw micrometer is often used as a medium for measuring objects such as layers, rods, blocks, and wire. So it can be known that the object that is nailed using this tool has a fairly low level of thickness.

  • Depth Micrometer

For this type of tool, it is used to measure the level of depth and height of an object. So for objects with holes, this thing can be used to measure the depth level of the hole.

Based on Scale :

  • Digital Screw Micrometer

A distinctive feature of this type of digital micrometer lies in the results of its measurements visualized on a digital screen. This certainly makes it easier for you to carry out measurement activities.

In terms of shape and size design, in general, digital micrometers have the exact same dimensions as analog / manual micrometers.

  • Analog / Manual Screw Micrometer

For this type, it has important components that you should pay attention to, namely the main scale and the nonius scale. The way to read an analog screw micrometer is to determine for yourself based on the result of the summation of the values designated by the needle of each scale.

How to Use a Screw Micrometer


There are 4 steps that you should pay attention to to using a screw micrometer. The first step is to attach the object to a fixed shaft, followed by turning the thimble, rotating the ratchet and reading the measurement results. You can see the details below:

  • Position objects between the Anvil and axis


The first step of a series of ways to use a screw micrometer is to place the object to be measured on a fixed shaft. Make sure that the position is correct.

The object to be measured in thickness is laid between the anvil and the axis. Then we adjust the rotation handle so that the object is firmly pinched, then we pull the lock towards the left so that there is no shift in position.


  • Rotate Thimble

After you are sure that the position of the object to be measured is in the right position, then the next step is to turn the thimble. This step is carried out until the object to be measured is sandwiched between the shear shaft and the fixed shaft.

To determine the magnitude of the measurement, we do the scale reading by reading a fixed scale first, with millimeters in units, that is, a fixed scale line that is right in front of the rotating handle.

  • Twisting Ratchet

In order to get more precise calculation results, then you can rotate the ratchet part of the measure. This is done by moving the sliding shaft section slowly.

On the reading of the rotary scale we will get a certain number then we multiply it by 0.01. It is this number of readings of fixed scales and rotary scales that are the result of measurements.

  • Reading Measurement Results

After you make sure that the object to be measured is properly squeezed in the middle of the two shafts, then the measurement results can be read.

The results of these measurements can be seen on the nonius scale and the main scale. When you are going to see a nonius scale, then look at the thimble section. While on the main scale, look at the sleeve section.

How to Read a Screw Micrometer

How to read a screw micrometer in general you can do with 3 steps. The first is to look at the position of the thimble on the main scale, then continue by looking at the position of the Nonius scale, and the last is to add up the two values.

In order to make it easier for you to understand how to read / calculate the correct screw micrometer, here we explain the details of the tutorial. Pay attention to the measurement image below:

Screw Micrometer Measurement

  • Looking at Thimble’s Position on a Major Scale

Pay attention to the screw micrometer image above, as a excuse, on the main scale of the thimble section it can be seen that the size has exceeded the number 5 at the top.

While on the lower side of the line whose direction is horizontal indicates that it has exceeded 1 strip or 0.5 mm. It shows that from the measurement results, 5 + 0.5 mm = 5.5 mm was obtained.

You need to understand, this measurement can be done by applying the principle if each strip shows a distance of 0.5 mm. In this example, on the upper side of the line whose direction is horizontal has passed 5 strips, while at the bottom there are 6 strips. Thus, a total distance of 5.5 mm is obtained.

  • Looking at the Position of the Nonius Scale

Still related to the previous excuse, how to read the screw micrometer on the horizontal line on the main scale is squeezed with the position of the number 28 on the nonius scale. Thus, in this part of the nonius scale there is an additional size of 0.28 mm.

  • Calculating measurement results

After you see the size on two scales, then you can already get the measurement results. If in accordance with the previous calculation, then a measurement result of 5.5 + 0.28 = 5.78 mm is obtained. The results of these measurements have a level of accuracy that reaches 0.01 mm.

Examples of How to Use a Screw Micrometer Correctly:

Take a look at the measurement image below!


How to read the measurement results of the screw micrometer in the picture above?

In the picture above, it can be seen that the marking on the main scale just to the left of the thimble is 7 mm. However, the division of half the scale seen below the main scale should not be simply ignored.

Thus the reading on the main scale will be 7.5 mm. For readings of the auxiliary scale, it is noted that the 22nd division on the thimble scale corresponds to the main scale.

Thus the scale reading on the thimble will be 0.22 mm. The last reading is the result of the sum of the two scales which is 7.5 + 0.22 = 7.72 mm.

To help you understand it, here we also include an example of how to measure / calculate a screw micrometer correctly.

Read Also Definition and Function of Barometer 

Examples of Screw Micrometer Calculation Problems

After understanding how to find out the size of a particular object using a micrometer measuring instrument. Here are some examples of screw micrometer problems that can be a guide when you encounter certain questions as below.

  1. Pay attention to the measurement picture of the screw micrometer below!


What is the final measurement?


It can be seen in the figure that the first part of the measurement is 2.5 mm, while the second part of the measurement is 0.38 mm

Ahir measurement = main scale + nonius scale

= 2,5 mm + 0,38 mm = 2.88 mm

  1. If it is known that the main scale of an object being measured shows a number of 4 mm on the main scale. While on the nonius scale shows a figure of 0.30 mm. So how many measurement results are obtained?


Measurement Results = main scale + nonius scale

= 4 + 0,30 = 4,30 mm

  1. Someone wants to measure the thickness of a wire made of copper. If the measuring instrument shows the main scale numbers worth 1.5 mm and the nonius scale is 0.30 mm long. Then what is the thickness level of the wire is….


Measurement Results = main scale + nonius scale

= 1,5 + 0,30 = 1,80 mm

  1. The welder measures the metal slab whose results look like the picture below. Determine how much thickness of metal the welder measures!



Main scale = 4 mmPlay scale = 34 x 0.01 mm = 0.34 mm Measurement Results = 4 + 0.34 = 3.34 mm

  1. Pay attention to the two screw micrometer images below!


The figure above shows that the reading at the bottom is the result of the measurement obtained, while for the reading at the top it is 0 errors. What is the actual measurement value?


Compensation measurement formula 0 error :

“Correct reading = Reading earned – Zero errors”

Where :0 The error can be either negative (the “0” sign on the thimble is above the datum line) or positive (the “0” sign on the thimble is below the datum line)

Measurement with zero error is 1.76 mm

Zero error: + 0.01 mm (positive because the zero mark on the thimble is below the datum line)

The actual measurement result is: 1.76 – (+0.01) = 1.75 mm

You need to understand, a screw micrometer can be used to measure the diameter or thickness of certain objects with a small size at a level of precision up to 25 mm long.

The conclusion that we can take from the article how to calculate a screw micrometer above is that not just any object can be measured using this tool. However, this tool has had a considerable contribution in the measurement of micro-sized objects / that have a fairly small size.


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