Login / Register to access your benefits
Recently searched
      • Published 13 Oct 2023
      • Last Modified 12 Feb 2024
    • 14 min

    A Complete Guide To Ball Bearing Measurement, Bearing Sizes And Bearing Codes

    Measuring a Ball Bearing using a caliper

    Ball bearings are essential components in many mechanical systems, including vehicles, industrial machinery, and household appliances. They help reduce friction and allow for smooth movement between two surfaces. Selecting the correct ball bearing is vital for various reasons, as it directly affects the performance, efficiency, safety, and potential downtime of a wide range of machines and equipment. To ensure proper functioning, it is important to know the type and size of a ball bearing.

    This guide aims to assist, you the customer in measuring ball bearings accurately to make sure you select the correct bearing for your specific application. Proper measurement is crucial in identifying the appropriate ball bearing size and type, as well as interpreting bearing codes to make an informed choice. Let’s go through the step-by-step process of measuring a ball bearing and understanding bearing codes.

    Identify The Type Of Ball Bearing

    Before measuring, it’s important to identify the type of ball bearing you have. There are several common types, such as deep groove ball bearings, angular contact ball bearings, and thrust ball bearings to mention a few. Each type has its own unique design, and it is essential to recognize the correct type you have for accurate measurements. For more information on the different types of ball bearings available please see our Ball Bearings Guide

    How To Measure A Ball Bearing

    Ball bearings usually have their identification code stamped or lasered on the outside diameter of the bearing itself, using this is the best way to ensure you select the right bearing.

    However, over time this code can become illegible or possibly worn away. So, it is important to be able to measure a ball bearing correctly.

    Determining the size of a ball bearing can be done by measuring its outer diameter (OD), bore size (ID), and width. These measurements are usually expressed in millimetres (mm). Using a calliper or a micrometer, you can accurately measure these dimensions.

    Tools you’ll need

    1. Calliper or Micrometer (digital or manual)
    2. Notepad and pen for recording data
    3. Flat and clean surface for measurement

    Step 1: Prepare Your Equipment

    Zero or calibrate your digital calliper or micrometer according to the manufactures instructions.

    Step 2: Measure The Bore Size - Inner Diameter (ID)

    Place the ball bearing on a flat and clean surface. Take the caliper or micrometer and gently insert its jaws or anvils into the bore of the bearing. Ensure that the measuring tool is at a right angle to the bore. Once positioned correctly, read, and record the measurement displayed on the caliper or micrometer. This value represents the bore size or the Inner Diameter (ID) of the bearing.

    Step 3: Measure The Outer Diameter (OD)

    Next, measure the outer diameter of the ball bearing. Position the measuring tool on the flat surface and place the outer edges of the caliper or micrometer jaws or anvils against the opposite sides of the bearings outer surface. Ensure the tool is at a right angle to the bearing. Read and record the measurement displayed on the caliper or micrometer. This value represents the outer diameter of the bearing.

    Step 4: Measure The Width (thickness)

    For ball bearings with a cylindrical shape, measure the width or thickness of the bearing. Place the bearing on a flat clean surface and align the jaws or anvils of the measuring tool against opposite sides of the bearing. Read and record the measurement displayed on the caliper or micrometer. This value represents the width of the bearing.

    Bearing Codes

    So, what does the code on your bearing actually signify? Let’s dig a little deeper and explain in a bit more detail.

    Typically bearing codes are comprised of a ‘basic number’ and depending on the bearing they can have supplementary codes at the beginning or the end of the basic number. These are the prefix and suffix codes.

    The basic number will give you general information about the bearing such as the type, series number and bore size.

    We will use a popular bearing (S) (6001) (2RS) as our example

    bearing code image reference

    Start by breaking down the code on your bearing into 3 parts

    1. S (prefix)
    2. 6001 (basic number)
    3. 2RS (suffix)

    Prefix

    Bearings very rarely have a prefix code. However, you may come across one that does. The prefix is used to highlight the parts used by the manufacturer in the design of the bearing. In our example where we have a Prefix of (S) it tells us that the bearing was made using stainless steel. Below are a couple of common examples


    Prefix

    Meaning

    W

    Stainless Steel (SKF)

    S

    Stainless Steel (FAG)

    Basic Number First Digit

    The first digit of the basic number tells you about the type of bearing you have. In our example, it’s (6) So this tells us it’s a Single row deep groove ball bearing.


    Bearing Type Code

    Bearing Name

    1

    Self-aligning Ball Bearing

    2

    Spherical Roller Bearing

    3

    Double Row Angular Contact Ball Bearing

    4

    Double Row Ball Bearing

    5

    Thrust Ball Bearing

    6

    Single Row Deep Groove Ball Bearing

    7

    Single Row Angular Contact Bearing

    8

    Felt Seal Bearing

    N

    Cylindrical Roller Bearing

    NN

    Double Row Roller Bearing

    NA

    Needle Roller Bearing

    BK

    Needle Roller Bearing with closed end (drawn cup)

    HK

    Needle Roller Bearing with open ends (drawn cup)

    C

    CARB Toroidal Roller Bearings

    QJ

    Four-point Contact Ball Bearing

    Basic Number Second Digit

    The second digit of the basic number tells us what series the bearing is from and is used to signify how tough the bearing is. In our example, it’s (0) Which tells us its extra light toughness.


    Series Code

    Series Code Meaning

    0

    Extra Light

    1

    Extra Light Thrust

    2

    Light

    3

    Medium

    4

    Heavy

    8

    Extra Thin Section

    9

    Very Thin Section

    Basic Number Third And Fourth Digit

    The third and fourth digits tell you the bore size or (ID) of the bearing you have. In our example, it’s (0) which tells us the bearing has a 12 mm bore size.

    Important Note that from 20mm and above you would need to times (x) the last 2 digits by 5 to ascertain the bore size for nearly all types of bearing.


    Third and Fourth Digit

    Bore Size (mm)

    00

    10

    01

    12

    02

    15

    03

    17

    From hereafter (x5)

    04

    20

    05

    25

    And so on………

    Suffix

    Suffixes indicate bearings with additional special characteristics or designs. They are typically used to provide information about how the bearing is sealed. In our example, it’s (2RS) which tells us our bearing is sealed on both sides.


    Suffix

    What do they mean?

    Z

    One side of the bearing is shielded

    ZZ

    Both sides of the bearing is shielded

    RS

    One side of the bearing is sealed

    2RS or DDU

    Both sides of the bearing is sealed

    C3

    Larger clearance

    K

    Taper bore

    NR

    Snap ring groove

    M or MB

    Machined brass cage

    Clearance Codes

    In some cases, your bearing may have an additional suffix such as C3. This can be found on the outside diameter of the bearing except in the case of CN. This refers to the bearings clearance code. See the table below for examples.

    clearance Image

    Suffix

    Clearance

    C1

    Less than C2

    C2

    Less than normal

    CN

    Normal

    C3

    Greater than normal

    C4

    Greater than C3

    C5

    Greater than C4

    It is important to note that different manufacturers can have their own specific Prefix and Suffix codes. Our tables give you some examples of the most common codes. If in doubt please check with the manufacturer of your bearing for exact information.

    Table Of Sizes

    So now you have a better understanding of how to measure a ball bearing and how to interpret a bearing code, why not check out our great range of high-quality bearings from industry-leading brands such as SKF, NSK, FAG, INA and of course our own brand RS PRO.

    We have created a list of the most popular sizes to make it quicker and easier for you to identify and purchase the exact ball bearing for your application. Simply click on your size and view our current selection.

    Single Row Deep Groove Ball Bearing Measurements


    Size

    Inner Dimension (mm)

    Outer Dimension (mm)

    Width (mm)

    604

    4

    12

    4

    Shop All 604 Bearings

    606

    6

    17

    6

    Shop All 606 Bearings

    607

    7

    19

    6

    Shop All 607 Bearings

    608

    8

    22

    7

    Shop All 608 Bearings

    609

    9

    24

    7

    Shop All 609 Bearings

    623

    3

    10

    4

    Shop All 623 Bearings

    624

    4

    13

    5

    Shop All 624 Bearings

    625

    5

    16

    5

    Shop All 625 Bearings

    626

    6

    19

    6

    Shop All 626 Bearings

    627

    7

    22

    7

    Shop All 627 Bearings

    628

    8

    16

    5

    Shop All 628 Bearings

    629

    9

    26

    8

    Shop All 629 Bearings

    686

    6

    13

    5

    Shop All 686 Bearings

    6000

    10

    26

    8

    Shop All 6000 Bearings

    6001

    12

    28

    8

    Shop All 6001 Bearings

    6002

    15

    32

    9

    Shop All 6002 Bearings

    6003

    17

    35

    10

    Shop All 6003 Bearings

    6004

    20

    42

    12

    Shop All 6004 Bearings

    6005

    25

    47

    12

    Shop All 6005 Bearings

    6006

    30

    55

    13

    Shop All 6006 Bearings

    6007

    35

    62

    14

    Shop All 6007 Bearings

    6008

    40

    68

    15

    Shop All 6008 Bearings

    6009

    45

    75

    16

    Shop All 6009 Bearings

    6010

    50

    80

    16

    Shop All 6010 Bearings

    6011

    55

    90

    18

    Shop All 6011 Bearings

    6012

    60

    95

    18

    Shop All 6012 Bearings

    6013

    65

    100

    18

    Shop All 6013 Bearings

    6014

    70

    110

    20

    Shop All 6014 Bearings

    6015

    75

    115

    20

    Shop All 6015 Bearings

    6016

    80

    125

    22

    Shop All 6016 Bearings

    6017

    85

    130

    22

    Shop All 6017 Bearings

    6018

    90

    140

    24

    Shop All 6018 Bearings

    6020

    100

    150

    16

    Shop All 6020 Bearings

    6200

    10

    30

    9

    Shop All 6200 Bearings

    6201

    12

    32

    10

    Shop All 6201 Bearings

    6202

    15

    35

    11

    Shop All 6202 Bearings

    6203

    17

    40

    12

    Shop All 6203 Bearings

    6204

    20

    47

    14

    Shop All 6204 Bearings

    6205

    47

    52

    15

    Shop All 6205 Bearings

    6206

    30

    62

    16

    Shop All 6206 Bearings

    6207

    35

    72

    17

    Shop All 6207 Bearings

    6208

    40

    80

    18

    Shop All 6208 Bearings

    6209

    45

    85

    19

    Shop All 6209 Bearings

    6210

    50

    90

    20

    Shop All 6210 Bearings

    6211

    55

    100

    21

    Shop All 6211 Bearings

    6212

    60

    110

    22

    Shop All 6212 Bearings

    6213

    65

    120

    23

    Shop All 6213 Bearings

    6214

    70

    125

    24

    Shop All 6214 Bearings

    6215

    75

    130

    25

    Shop All 6215 Bearings

    6216

    80

    140

    26

    Shop All 6216 Bearings

    6217

    85

    150

    28

    Shop All 6217 Bearings

    6218

    90

    160

    30

    Shop All 6218 Bearings

    6220

    100

    180

    34

    Shop All 6220 Bearings

    6222

    110

    200

    38

    Shop All 6222 Bearings

    6300

    10

    35

    11

    Shop All 6300 Bearings

    6301

    12

    37

    12

    Shop All 6301 Bearings

    6302

    15

    42

    13

    Shop All 6302 Bearings

    6303

    17

    47

    14

    Shop All 6303 Bearings

    6304

    20

    52

    15

    Shop All 6304 Bearings

    6305

    25

    62

    17

    Shop All 6305 Bearings

    6306

    30

    72

    19

    Shop All 6306 Bearings

    6307

    35

    80

    21

    Shop All 6307 Bearings

    6308

    40

    90

    23

    Shop All 6308 Bearings

    6309

    45

    100

    25

    Shop All 6309 Bearings

    6310

    50

    110

    27

    Shop All 6310 Bearings

    6311

    55

    120

    29

    Shop All 6311 Bearings

    6312

    60

    130

    31

    Shop All 6312 Bearings

    6313

    65

    140

    33

    Shop All 6313 Bearings

    6314

    70

    150

    35

    Shop All 6314 Bearings

    6315

    75

    160

    37

    Shop All 6315 Bearings

    6316

    80

    170

    39

    Shop All 6316 Bearings

    6317

    85

    180

    41

    Shop All 6317 Bearings

    6318

    90

    190

    43

    Shop All 6318 Bearings

    6319

    95

    200

    45

    Shop All 6319 Bearings

    6320

    100

    215

    47

    Shop All 6320 Bearings

    6324

    120

    260

    55

    Shop All 6324 Bearings

    6800

    10

    19

    5

    Shop All 6800 Bearings

    6801

    12

    21

    5

    Shop All 6801 Bearings

    6802

    15

    24

    5

    Shop All 6802 Bearings

    6803

    17

    26

    5

    Shop All 6803 Bearings

    6804

    20

    32

    7

    Shop All 6804 Bearings

    6805

    25

    37

    7

    Shop All 6805 Bearings

    Self Aligning Ball Bearing Measurements

    Single Row Angular Contact Ball Bearing Measurements

    Double Row Angular Contact Ball Bearing Measurements


    Size

    Inner Dimension (mm)

    Outer Dimension (mm)

    Width (mm)

    3200

    10

    30

    14

    Shop All 3200 Bearings

    3201

    12

    32

    15.9

    Shop All 3201 Bearings

    3202

    15

    35

    15.9

    Shop All 3202 Bearings

    3203

    17

    40

    17.5

    Shop All 3203 Bearings

    3204

    20

    47

    20.6

    Shop All 3204 Bearings

    3205

    25

    52

    20.6

    Shop All 3205 Bearings

    3206

    30

    62

    23.8

    Shop All 3206 Bearings

    3207

    35

    72

    27

    Shop All 3207 Bearings

    3208

    40

    80

    30.2

    Shop All 3208 Bearings

    3209

    45

    85

    30.2

    Shop All 3209 Bearings

    3210

    50

    90

    30.2

    Shop All 3210 Bearings

    3304

    20

    52

    22.2

    Shop All 3304 Bearings

    3305

    25

    62

    25.4

    Shop All 3305 Bearings

    3306

    30

    72

    30.2

    Shop All 3306 Bearings

    3307

    35

    80

    34.9

    Shop All 3307 Bearings

    3308

    40

    90

    36.5

    Shop All 3308 Bearings

    Summary

    In conclusion, mastering the art of measuring ball bearings and understanding bearing codes is vital for anyone involved in mechanical or industrial applications. By following the steps outlined in this guide, you can confidently and accurately determine crucial parameters like inner and outer diameters, width, and radial play.

    Furthermore, decoding bearing designations enables you to select the right bearing for your specific needs, optimizing performance and longevity. Remember that precision is paramount, and a well-measured bearing is essential for efficient machinery and reliable operation.

    Malcolm Watson Image

    Reviewed by Malcom Watson (Technical Product Engineer for RS Group)

    I have over 40 years of experience in Mechanical Power Transmission specialising in Bearings (covering Technical roles and Product Management). I am always motivated to learn more as new bearing innovations are regularly introduced to the market by our leading brands offering even better solutions to customers. Improving downtime and increasing efficiency. Keeping industry moving!

    Further Reading

    Related links