How to Identify an SKF Bearing: A Complete Guide to Bearing Codes and Dimensions

You may need to replace a bearing when the code engraved on the ring is no longer legible. After years of operation, the markings can become worn due to wear, oxidation or cleaning with solvents, making it impossible to identify the exact model.

In these cases, there is no need to rely on trial and error. Using a simple vernier caliper, you can measure the bearing’s key dimensions and, in most cases, identify the correct model.

In this guide, we will explain how to measure a bearing, how to interpret the main SKF bearing designations, and which checks to carry out before ordering a replacement.

WHEN IS IT NECESSARY TO MEASURE A BEARING?

Measuring a bearing becomes essential when:

• the engraved code is illegible or completely worn away;

• the bearing is heavily worn;

• you are repairing an older machine for which the original spare parts are no longer available;

• you want to check the compatibility of an existing bearing.

Correct identification helps prevent purchasing errors, reduce machine downtime and ensure that the most suitable component is installed for the application.

The three key dimensions

To identify a bearing, three dimensions are generally required:

• Bore diameter (d): corresponds to the diameter of the shaft on which the bearing will be mounted.

• Outside diameter (D): corresponds to the diameter of the housing bore.

• Width (B): represents the overall width of the bearing.

How to Measure a Bearing Correctly

To obtain reliable measurements, it is advisable to use a digital caliper with a precision of one tenth or, preferably, one hundredth of a millimetre.

Measuring the Bore Diameter

Position the internal jaws of the caliper inside the inner ring and make sure they are in full contact with the surface. Avoid tilting the caliper, as this could result in an inaccurate measurement.

Measuring the Outside Diameter

Place the external jaws of the caliper on the widest part of the bearing, keeping the caliper perfectly perpendicular.

Measuring the Width

Measure the overall width of the bearing between its two outer faces.

Once you have obtained these three measurements, you can already significantly narrow down the number of compatible bearing models.

How to Read an SKF Bearing Code

When the code is still legible, even if only partially, it can provide a great deal of useful information.

Let’s take a very common code as an example:6205-2RS1

The designation can be interpreted as follows:

• 6 → single-row deep groove ball bearing;

• 2 → dimension series;

• 05 → bore diameter;

• 2RS1 → rubber seals on both sides.

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Even if part of the marking has worn away, being able to read just a few digits may be enough to identify the correct bearing model.

How to Interpret the Last Two Digits

In the most common bearings, the last two digits indicate the bore diameter.

Code	Bore Diameter
00	10 mm
01	12 mm
02	15 mm
03	17 mm
04	20 mm
05	25 mm
06	30 mm
07	35 mm
08	40 mm
09	45 mm
10	50 mm

From code 04 onwards, simply multiply the last two digits by 5.

For example:

• 6208 → 8 × 5 = 40 mm

• 6212 → 12 × 5 = 60 mm

• 6216 → 16 × 5 = 80 mm

This rule often makes it possible to quickly check whether the identified bearing code is consistent with the measured dimensions.

The Most Common SKF Suffixes

In addition to dimensions, the bearing designation contains important information about the bearing’s design and features.

Suffix	Meaning
2RS1	Rubber seals on both sides
2Z / ZZ	Metal shields on both sides
C3	Greater than Normal internal clearance
TN9	Glass fibre reinforced polyamide cage
E	Increased load-carrying capacity
NR	Snap ring groove with snap ring

These suffixes should not be overlooked: two bearings with the same dimensions can have very different performance characteristics.

Important: Dimensions Alone Are Not Always Enough

It is a common mistake to assume that two bearings with identical dimensions are necessarily interchangeable.

In addition to the dimensions, you should also consider:

• seal type;

• internal clearance;

• cage material;

• manufacturing accuracy;

• rotational speed;

• load-carrying capacity.

For this reason, when the bearing designation is still partially legible, it is always advisable to provide it together with the measured dimensions.

The Most Common Measuring Mistakes

When measuring a worn bearing, it is easy to make some common mistakes:

• measuring over the seals instead of the bearing ring;

• using a caliper that is not perfectly aligned;

• taking measurements from a deformed or damaged bearing;

• ignoring the suffixes or markings still visible on the bearing;

• ordering a replacement based solely on its dimensions.

Careful identification helps prevent incorrect replacements and further machine downtime.

Tecnofluid Can Help You Identify Your Bearing

If the code on your bearing is no longer legible, our technical team can help you identify the correct replacement.

Simply send us:

• a photograph of the bearing;

• the bore diameter;

• the outside diameter;

• the width;

• any parts of the designation that are still legible.

Thanks to our extensive experience in supplying components for industrial maintenance and the availability of thousands of references from leading manufacturers, we can quickly identify the most suitable component for your application and recommend the right solution.

Need help identifying a bearing? Contact Tecnofluid: our technical team is available to help you find the correct replacement.

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