Bearing part Numbers

Bearings support mechanical rotating bodies, thus reducing their coefficient of friction during movement and ensuring better accuracy of rotation. Bearings are used in a wide range of mechanical applications and adhere to standardized designs and international regulations. International bodies like ISO and ANSI regulate a portion of bearing’s regulations, leaving innovation space for manufacturers and a chance to develop unique designs that are specifically devised to help distinguish themselves from other producers.

However, there aren’t strict standards for bearing part numbers, resulting in unique part number schemes specific to each manufacturer. Therefore, to replace a bearing from one manufacturer to another is not always straightforward based on the part number. The process of decoding the part numbers in a roller bearing series is discussed below.

Meaning of numbers in bearing series

The designation of a roller bearing part number consists of a basic number, surrounded by auxiliary codes- suffixes and prefixes, which describe the internal clearance, tolerance, and other design parameters.

A bearing part number typically has 3 to 5 digits. These digits typically inform the following:

1. Type of bearing
2. Bearing size
   1. Width (B, C, T, or H)
   2. Outer diameter (D)
   3. Bore diameter (d or de)
   4. Chamfer dimensions (R)
3. Series number
4. Contact angle

As an example, the typical bearing part numbering will look like 'A BC DE.' Consider an example shown in Figure 2. The overall bearing designation looks like Prefix A BC DE suffix.

The suffix and prefix are separated from the rest of the designation number by a hyphen, space, or an oblique stroke. Figure 2 shows the bearing part number as S 1 27 02 2, decoded as follows:

• S: Prefix, which precedes a typical bearing part number
• A: Bearing type symbol, equal to 1
• BC: Bearing size, with width series symbol 2 and outer diameter series symbol 7
• DE: Bore diameter code, equal to 02
• 2: Suffix, which succeeds a typical bearing part number.

The width and the outer diameter (BC) are internationally standardized, also referred to as the dimensional series of the bearing. The dimensional series (BC), together with the bearing type (A), is referred to as the bearing series symbol (ABC).

The individual parts of a bearing part number can be compared against the values given in the tables below to get adequate information about the bearing being used.

If the diameter of the bore is greater than 20mm, multiply the bore diameter (which is given as a two-digit code DE) with 5 to get the actual bore diameter in mm. For bore diameters less than this value, use the code identifications in Table 1.

Bearing code identification

Table 1: Bearing code identification if the bore diameter< 20 mm

Bore Diameter	10 mm	12 mm	15 mm	17 mm
Code	00	01	02	03

Codes for bearing types

The codes used for bearing types are represented in Table 2 and are satisfactorily agreed upon throughout the industry.

• The letters BC represent the size of the external diameter of the bearing and how wide it is.
• The series numbers go from 7-8-9-0-1-2-3-4 for the outer diameter, with 7 being the smallest diameter and 4 the largest.
• The codes go from 8-0-1-2-3-4-5-6 for the width of radial bearings, with 8 being the smallest width and 6 the largest.
• The codes go from 7-9-1-2 for the height of thrust bearings, with 7 being the smallest and 2 the biggest.

Prefixes are used to define the variations or components of a bearing. Suffixes indicate design parameters like bearing external or internal design (seals, snap ring groove), materials and heat treatment, cage design, and clearance. Tables 3-5 show common prefixes and suffixes used in roller bearing designations.

Table 2: Codes used for bearing types

Bearing Type	SKF	NSK	Timken	FAG
Double row angular contact ball bearing	0	3,5		3
Self-aligning ball bearing	1	1	1,2	1
Spherical roller bearing, spherical roller thrust bearing	2	2	2	2
Tapered roller bearing	3	3	3	3
Double row deep groove ball bearing	4	4		4
Thrust ball bearing	5	5	5	5
Single row deep groove ball bearing	6	6	6	6
Single row angular contact ball bearing	7	7	7	7
Cylindrical roller thrust bearing	8		8
CARB toroidal roller bearing	C
Cylindrical roller bearing	N	NU, N, NU, NN	NU, NN, N, NF	N, HCN, NN, NNU
Four-point contact ball bearing	QJ			QJ
Tapered roller bearing in accordance with ISO 355	00	01	02	03
Separable ball bearing		BO, E, L

Common prefixes and suffixes used in roller bearing designations

Table 3: Prefixes- NSK Bearings

Meaning	Bearing with special dimensions	Bearing with flanged outer ring	Higher load rating	Miniature metric bearing with special dimensions	Bearing outer ring with rollers and cage, no inner ring	Miniature bearing made from extra corrosion-resistant steel
Code	B	F	HR	MR	R	-H-
Table 4: Suffixes- Clearance
Meaning	Normal radial internal clearance (RIC)	Radial internal clearance smaller than C2	Radial internal clearance smaller than normal radial internal clearance greater than normal	Radial internal clearance greater than normal	Radial internal clearance greater than C3	Radial internal clearance greater than C4
Code	C0/CN	C1	C2	C3	C4	C5

Table 5: Suffixes used by established brands