Choosing the Right Micrometer

These are the main criteria to consider when choosing a micrometer:

Type of micrometer

There are different types of micrometers. Your choice will depend on your intended use:

• An outside micrometer is used to measure the outside dimensions of an object.
• An inside micrometer is used to measure the inside dimensions.
• A depth micrometer is used to measure grooves and holes, even the deepest ones.

Measuring range

The measuring range of micrometers can be from a few millimeters to several centimeters, depending on the model. Make sure you choose a micrometer that is suitable for the dimensions of the parts you need to measure.

Precision and resolution

The accuracy and resolution of the micrometer are two fundamental characteristics. Precision corresponds to the degree of accuracy with which the micrometer can take measurements and depends on the quality of the instrument’s manufacture. Resolution, also called graduation, is expressed in micrometers (or microns) and indicates the smallest variation the instrument can measure. The resolution of the micrometer directly influences its accuracy. In other words, the higher the resolution, the more accurate the measurements.

Measuring system

Micrometers can have scales in millimeters or inches, depending on the country.

Zeroing

On certain micrometers, it is possible to manually adjust the zero point to compensate for wear or to calibrate the device.

Display

The most common micrometers are vernier-type, using a fixed scale and a sliding scale. The most modern models have digital displays, which allow for a more accurate and faster reading.

Ergonomics

Ease of use and user comfort in cases of frequent use are important factors to consider when choosing a micrometer.

Price

The price of micrometers varies according to the quality and characteristics of the device.

There are three main types of micrometers, each with different applications.

Outside micrometers

As the name suggests, these are used to measure the outside dimensions of an object, such as its length, width, thickness, or external diameter. They consist of an anvil (fixed) and a spindle (movable), which adjusts around the part to be measured.

Inside micrometers

These are used to measure the inside dimensions of a part, such as the diameter of a hole. There are internal two-point micrometers, three-point micrometers, and other caliper-type micrometers, with two movable points that move closer and further apart to adjust to the part being measured.

Depth micrometers

These are used to measure the depth of a hole, groove, or notch.

They have a rod that is inserted into the workpiece to measure the depth precisely.

Micrometers can be digital or analog. The choice depends on the user’s preference, the intended applications, and the precision required for the job. Digital micrometers have the advantages of precision and ease of use, while analog micrometers stand out for their durability and low cost. Some professionals work with both, using one or the other according to the measurement needs in each case.

Below are the main advantages of each.

Digital micrometers

These micrometers have a digital display, which shows the measurements with great precision and makes them easy to read.

They are recommended for jobs where quick measurement readings are required.

Advantages:

• They take precise measurements with a resolution of up to one-tenth of a micrometer (0.0001 mm).
• The digital screen makes it easier to read the results and reduces the risk of reading errors due to human factors, particularly parallax errors, which are more likely to occur with analog micrometers.
• Some digital micrometers allow you to easily switch between units of measurement, i.e. between millimeters and inches.
• Some models have a memory for storing a certain number of measurements, which can be useful for monitoring data or preparing reports.
• There are also micrometers with advanced functions, such as tolerance and automatic zero.
• Digital screens are generally backlit and offer good contrast, allowing you to read the results even in difficult lighting conditions and with vibrations.

Analog micrometers

Advantages:

• These are robust and resistant to impacts, vibrations, and, in general, extreme conditions in industrial environments.
• Their price is lower than that of digital models, which may be a determining factor for some users.
• They don’t need batteries to work.
• They allow continuous reading.
• Due to their simple mechanical construction, they generally require less maintenance than digital micrometers.

An optical micrometer operates similarly to the previous types, except that it measures without physical contact with the object, which is placed between the emitter of the light beam and the receiver. It is a non-intrusive method that allows high-precision measurements to be taken without the risk of damaging fragile objects.

An optical micrometer is a good choice for applications where extremely precise measurements are required, as detailed below. We also mention some of their main applications.

High precision

Optical micrometers make it possible to take measurements with a resolution/gradation of a few micrometers (or less than one micrometer, for devices intended for sub-micrometer measurements).

Applications:

• Research
• Engineering
• Manufacturing
• Nanotechnology
• Microelectronics
• Cell biology
• Surface inspection

Optical micrometers are very useful for inspecting surfaces in detail to detect and measure roughness, defects, scratches, etc.

Ball end micrometers

These have one or two spherical tips, a feature that makes them suitable for measuring the distance between a hole and the edge of a part, but also for taking precise measurements on curved or irregular surfaces, for example in metrology activities.

Blade micrometers

These are suitable for measuring grooves and special shapes. It is advisable to use them when you need to measure parts with complex contours with great precision.

Tube micrometers

These have a long anvil that forms a 90º angle to the micrometer spindle. They are used to measure the thickness of pipe walls. They take fast and highly accurate measurements.