What is a Bearing?

A bearing is a mechanical component used to facilitate rotation between two parts. It reduces friction between moving parts, which helps improve the efficiency and lifespan of machines and equipment.

Bearings generally consist of an inner ring, an outer ring, and rolling elements such as balls, rollers, or needles housed between the two rings. Ball bearings are the most commonly used type. Regardless of the bearing type, they are manufactured in a variety of sizes to suit different applications.

Why Measure a Bearing?

Generally, the bearing's part number is inscribed directly on it. The part number can be engraved on the rings, the seal, or the shield. If your bearing does not have a part number, the only remaining solution to identify it is to take its measurements.

Measuring a bearing can be done using a caliper, which is the most accurate tool for the job. This tool allows you to measure the inner diameter, outer diameter, and width of the bearing.

What are the Steps to Measure a Bearing?

1. Get a caliper. This is the must-have tool for taking precise bearing measurements. You can opt for an analog caliper or a digital caliper, which directly displays the measured value.

2. Measure the inner diameter of the bearing. To do this, position the inside jaws of the caliper against the walls of the inner ring. You can then take the corresponding measurement. When reading an analog caliper, two scenarios are possible: the measurement is a whole number, or it is a decimal number.

If it is a whole number, the 0 on the sliding scale will align perfectly with one of the lines on the fixed scale. For example, 20 mm, as shown below.

If it is a decimal number, look at the closest line to the left of the 0, which will give you the whole number part of your measurement. For the decimal part, find the graduation mark on the sliding scale that perfectly aligns with one of the lines on the fixed scale. For example, 20.5 mm, as shown below.

3. Measure the outer diameter of the bearing. Position the outside jaws across the outer diameter and read the measurement as before.

4. Measure the width of the bearing. Turn the bearing on its side so it is in profile facing you, place the outside jaws on each side of the bearing, and read the corresponding measurement.