Micrometer Guide 101: How to Read and Use a Micrometer Properly

How to Read and Use a Micrometer

Though it looks like something from a medieval torture chamber, almost every veteran machinist swears that a micrometer is the best tool in their toolbox. If you need precise measurements, using a micrometer can help a lot. A micrometer is the simplest way to get an accurate measurement to within 0.001 inches. So how do you use a micrometer? The numbers on the thing don’t make any sense, right? Well, I am here to change that. Today we’ll learn about how to read and use a micrometer the right way.

So let’s get to know this amazing and versatile weapon of modern engineering. Shall we begin?


What is a Micrometer?

To be honest, a micrometer is nothing but a measuring scale. What’s special about this handy little device is its high precision to take exact measurements. The process is simple enough. A micrometer has a hard stop (anvil) and a movable surface (spindle). You can drive the spindle closer or farther away from the anvil by turning the big, screwlike thimble lock.

The device can be divided into two parts. The stationary part contains the anvil, lock nut, and sleeve, and the moving part contains the spindle, thimble, and ratchet. A traditional analog micrometer will have the scale engraved into its body. As most of the traditional micrometers follow the English/metric unit, many know the tool as an English Micrometer as well.


How To Use

Believe it or not, using a micrometer is the easy part of the process. To measure any dimension, you just have to place the object between the anvil and the spindle. Then spin the thimble until the object is gently pinched between the two faces. Once the object is pinched so that it doesn’t fall on its own, you are ready to take the reading.

Though many users complain that the device requires a third hand, once you know how to hold and take care of your micrometers, you’ll be able to operate the tool with ease. Here’s a pro tip on how you can hold your common micrometer the right way. First, hold the tool in your dominant hand. Then, grasp the thimble between your thumb and index fingers. Don’t forget to place the C-shape of the frame against your palm. Wrap your pinky/ring finger within the inside of the frame and use your thumb and index finger to spin the thimble.

But when it comes to larger micrometers, try to find the perfect balance point, so you don’t strain your wrist too much. Now use the other hand to place the object between the anvil and the spindle of your micrometer. Try not to cover the sleeve with your palm, as that will make it hard to take the measurements. If you are using a digital micrometer, don’t forget to turn it off once you are done. And try to avoid using electric pens to engrave the body. This may hamper the device’s circuit. Use a damp and soft cloth to clean the tool.


How To Read

Here comes the tricky part. Taking accurate reading on a micrometer is a bit complicated. Let’s try to understand the process step-by-step. Look closely, and you’ll find either a horizontal line or a scale engraved on your device.

This scale is called a sleeve scale, and the line is named “datum line.” This is a linear scale that shows how far away the spindle is from the anvil. So hitting “0” means there is no empty space between the spindle and the anvil.

On traditional English micrometers, each dash on this scale represents .025² (25 thousandths of an inch), and the large numbers represent .100² (100 thousandths of an inch).

There is another scale on the micrometer. This rotary scale is located along the device’s circumference, and each line on this scale represents .001² (1 thousandth of an inch). There are in total 25 lines on that scale, and it can move along the spindle by rotation. One revolution of the spindle corresponds to .025² or one line on the datum line. So when you rotate the spindle for a whole turn, one line will be covered/uncovered in the linear scale below. Sounds simple enough, right?

Now let’s get into how to decipher the weird yet simple mechanism. Once you hold an object between the spindle and the anvil, you’ll hear 1/2 soft clicks indicating that the right amount of force/tension is applied. If you want, you can secure the position by using the lock nut. Now, look at the lines on the micrometer spindle and find out which markings are aligned with the datum line. Let’s imagine you can see only one small line after crossing the number 3. What would be the reading then?

Well, that’s simple. The largest number you can see on the datum line is 3, right? This corresponds to .300 inches. After that, count the number of dashes on the datum line between the last large number and the spindle. In our case, that’s just one, representing .025 inches. Lastly, read the number on the spindle that is aligned with the datum line.

Let’s imagine the number crossed was 2 past 15. Meaning we’ve completed 17 dashes/lines on the rotary scale, right? Now, as each line on that scale is equal to .001², our reading will be =

((15+2) * .001), or .017².

That’s it. You’ve successfully taken all the micrometer readings necessary. Now the last part of the job is to add all those three readings we’ve acquired. In our case, that would be = .300² + .025² + .017² = .342² inches.

Congratulations, now you know how to read and use a micrometer properly. Now let’s find out why we should bother to use such a tool. Shall we?


What’s the Use?

Things aren’t always this complicated. You can also use a digital micrometer to make the process more efficient. Now, why do you need one? Well, suppose you long for accurate and consistent measurements. In that case, this versatile tool can help you measure the inside width of a pipe, bearing, or another hollow object alongside outside dimensions and depth with great precision.

Imagine you are designing machines with moving parts, want to know the thickness of your lab equipment, or measure the depth of a sheet in the production line. All those cases need extremely accurate measurements. Micrometers thrive in this type of situation where the error margin must be as low as possible. This is one of the most basic and essential measurement tools for an engineer or a technician.


Types of Micrometer

Depending on what you want to do with it, there is a number of micrometers available in the market. Let’s have a look at some of the most prominent types of micrometers you can get your hands on.


Ball Micrometer:

These micrometers come with spherical anvils to correctly identify the measurement of alternative rounded surfaces. Though it’s a bit tougher to use, it gives more accurate results than most other types of tools.


Digital Micrometer:

This is a great tool for those who want a hassle-free and efficient experience. With these, you have to do complicated maths to get the final result. It’ll be directly shown on the LCD screen.

Blade Micrometers:

If you want to measure sharp objects, such as O-ring grooves, you’ll need one of these. These specially designed tools are particularly helpful when it comes to the measurement of specifically shaped objects.


Tube Micrometers:

This particular type of micrometer is designed to measure the thickness of tubes. They feature cylindrical anvils located perpendicular to the spindle.


Over To You

No More today. I hope you’ve got a pretty good idea about what a micrometer doesn’t and how to read and use a micrometer properly. Feel free to share your thoughts and experiences with us in the comment section below. Thanks for reading this far. Happy measuring to you.

Scroll to Top