The micrometer is a measuring tool commonly used in mechanics-related work environments. It is the instrument used, for instance, to measure a screw or a vehicle's axle. You can also find micrometers designed to gauge the inside width of a nut or the depth of a specific part.
You can choose a model based on the different levels of accuracy it offers. The most basic micrometers are precise to one hundredth of a millimeter, while the most accurate can calculate lengths of one thousandth of a millimeter – in other words, one micron. In this article, we will tell you everything there is to know about these tools.
- 1 Weekly newsletter with the best personal finance tips
- 2 Key Facts
- 3 Our Selection: The Best Micrometers
- 4 Shopping Guide: Everything You Should Know About Micrometers
- 4.1 What is a micrometer exactly?
- 4.2 What are the different parts of a micrometer?
- 4.3 What are the primary uses of the micrometer?
- 4.4 How does a micrometer work?
- 4.5 What types of micrometers are there?
- 4.6 What are the available micrometer sizes?
- 4.7 How do I read my micrometer?
- 4.8 What is the difference between the micrometer and the vernier caliper?
- 5 Shopping Criteria
- 6 Summary
- There are three basic types of micrometers, according to their use: inside, outside, and depth.
- You can choose between analog or digital models.
- Before you purchase a new micrometer, make sure that it comes with the measurement system – inches or millimeters – and range that you need.
Our Selection: The Best Micrometers
As we will discuss later, there are several types of micrometers on the market: inside, outside, and depth models. In addition, you can choose between the traditional mechanical tool or a digital product. In the following section, you will discover our very own selection of the best micrometers currently available out there.
Shopping Guide: Everything You Should Know About Micrometers
As you now know, micrometers can come in a variety of types and sizes. Designed to measure thickness and dimensions, the outside micrometer remains the most common. Let's now delve into what these tools are exactly and their main purposes. The information you will find in the section below will help you identify the right micrometer for your needs.
What is a micrometer exactly?
Some micrometers are accurate to one hundredth of a millimeter (0.01 mm). The more precise ones live up to their name and can measure down to a micron, or a thousandth of a millimeter (0.001 mm). You can find other tools that work similarly, such as the traditional Vernier caliper.
What are the different parts of a micrometer?
- Body. This consists of the arc and the frame of the micrometer. It usually has thermal insulation plates to prevent the material from expanding with the heat, which would affect its overall accuracy.
- Anvil. It is the end of the micrometer against which the sample rests.
- Spindle. This moving metal cylinder usually has its end hardened with a heavy-duty alloy.
- Lock nut. This is the locking system that allows you to immobilize the spindle.
- Sleeve, barrel, or stock. Attached to the body of the micrometer, this is the stationary part that contains a fixed scale (from 0 to 25 mm in the smallest tools).
- Thimble. It moves at the same time as the spindle and features an engraved scale with 50 divisions.
- Ratchet stop. Located at the end of the micrometer, it is designed to regulate the force that you will exert during the measurement.
What are the primary uses of the micrometer?
- Laboratory measurements
- Automobile repair shops
- Machinery calibration
On the other hand, the shape of the anvils determines other more specialized uses for high-precision measurements within the fields of mechanics and engineering. For example:
- Plane parallel anvils. These are commonly used to make measurements of flat surfaces in parallel.
- Conical anvils. They are designed to measure the space between the edges of a surface with a thread.
- Disc-shaped anvils. They help calculate the space between the teeth of a gearbox.
- Circular anvils. They are used to measure the diameter of small holes.
How does a micrometer work?
What the micrometer does is actually magnify the reading of very small lengths that would otherwise be extremely difficult to measure. To improve accuracy, subdivisions are included within the scale. This second scale allows you to fine-tune the measurement on the main scale.
What types of micrometers are there?
Type of measurement
- Outside micrometer. Most frequently found in industrial environments, it is used for external measurements: spheres, screws, wires, axles, and mechanical parts in general.
- Inside micrometer. Its role is to measure the diameter of spaces, such as bores or holes in the wall.
- Depth micrometer. As its name suggests, it calculates the inner depth of a part.
Type of reading
- Analog. This traditional micrometer has a mechanical operation.
- Digital. These models have the same shape and function, but the reading comes in the form of digits on a screen.
What are the available micrometer sizes?
The 25-mm micrometer is found in any automobile repair shop, but there are other sizes that follow a pattern of 25 millimeters. This means that, if the smallest tool has a measuring capacity of up to 25 mm, subsequent sizes have a range of 50 mm, 75 mm, and so on.
How do I read my micrometer?
- One full turn of the thimble moves the screw half a millimeter (0.5 mm), which is the diameter of the micrometer screw.
- The horizontal line on the handle features a scale graduated in millimeters. Each of these millimeters is divided into two below that line.
- The beveled edge has 50 graduations. Each one represents one hundredth of a millimeter (0.01 mm). The number scheme on the scale appears in steps of 5 to facilitate the reading.
- The most accurate micrometers include additional scales to measure hundredths (0.01) and even thousandths of a millimeter (0.001 mm).
What is the difference between the micrometer and the vernier caliper?
If we had to summarize the main difference between the two tools, we could say that the micrometer gains in precision, while the caliper gains in versatility. Choosing either one depends on the specific measurements you need to make. We have compared the two instruments in the table below:
|Precision||It can measure accurately to one hundredth of a millimeter (0.01 mm), or even to one thousandth of a millimeter (0.001 mm).||It isn't as precise as the micrometer. Its minimum graduation is two hundredths of a millimeter (0.02 mm).|
|Ease of use||The micrometer screw gauge doesn't require any special manual skills.||This extremely delicate measuring instrument requires a certain amount of handling skill.|
|Durability|| Its robust construction guarantees flawless operation without deformation.
The measuring ends (the anvil and the spindle) are made from a particularly hard alloy to prevent wear.
| You should avoid bending or scratching it.
Metal shavings must also be kept away, as they can get between the parts and damage the instrument.
|Versatility||Micrometers usually have one function: inside, outside, or depth.||The vernier caliper can measure dimensions in all 3 variants.|
A micrometer isn't necessarily something we have in our toolbox at home. This specialized measuring instrument is most common in work environments, and repair shops or jewelry making are trades that require the kind of precision that a micrometer offers. Here are some criteria to keep in mind when making your purchase:
Degree of Precision
Micrometers are usually accurate to within one hundredth of a millimeter (0.01 mm) or the equivalent in inches (0.00005"). If you don't need that much precision, you can opt for a vernier caliper. On the other hand, you can also find models that go down to one thousandth of a millimeter (0.001 mm). Evaluate your needs before settling for a specific model.
How you use this tool is a fundamental criterion in your final decision. As you already know, you have the possibility to choose between three different types of micrometers depending on their functionality: inside, outside, or depth. Remember that the external measurement of thickness and dimensions is the most common task.
The most subtle differences also fall within the outside micrometer category. Keep in mind what we discussed earlier regarding the different anvil types – parallel, conical, or circular – used to measure flat surfaces, threaded surfaces, or gear teeth, for instance.
Size of the Measured Parts
We have already looked at the different micrometer sizes that follow a progressive pattern of 25 in 25 millimeters. You may require different sizes if you work in a garage. In any case, the most common one remains the 25-mm micrometer both in mechanics and other trades that need precision.
You can naturally use a 50-mm model to measure 25-mm parts, but the smaller version will be more comfortable to use. If your work involves measuring components with significant differences in size, your best option might just be the vernier caliper – provided that you can settle for a maximum accuracy of 0.02 mm.
Digital or Analog
Mechanics professionals have been using the micrometer for decades now. Once you become skilled with the analog micrometer, you will tend to continue with this system. Standard micrometers are rugged and can withstand shocks better than any digital micrometer since they have no screens to be broken.
In our selection of products, you may have noticed that there is a wide variety of micrometers available on the market. Digital models integrate a backlit display to facilitate the reading in very bright environments. Besides, digital readers are capable of measuring in both millimeters and inches.
This is yet another essential factor that can lead to fatal errors if you neglect it during your purchase process. Indeed, if you use the metric system in your work, make sure that you don't choose a micrometer with the scales graduated in inches. Analog models will only feature one of the two measuring systems.
If you need both or want to avoid any potential confusion, choosing a digital micrometer will make all your worries disappear. This technology allows you to switch from millimeters to inches at the touch of a button. This type of micrometer saves you from converting units, which can be tedious and lead to measurement errors.
Not everyone has a micrometer in their toolbox. If you've come this far, you're probably a professional mechanic, a jeweler, or a DIY enthusiast. These tools will come in very handy whenever you need to measure the thickness of a screw or another small part. You now know exactly how they work and the different types available out there.
If you're thinking of buying a micrometer, make sure you consider the type of measurement you need to take: outside, inside, or depth. In addition, check that the tool uses the right measurement system: millimeters or inches. If you need both, a digital micrometer will perfectly do the trick.
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