Bearings are very common in our daily work; do you know how to distinguish between different bearing sizes and types based on their codes?
Classification of Bearings
The first digit (counting from left to right), or the sum of the first and second digits, indicates the bearing type:
"6" denotes a Deep Groove Ball Bearing (Series 0).
"4" denotes a Double-Row Deep Groove Ball Bearing (Series 0).
"2" or "1" denotes a Self-Aligning Ball Bearing (basic model consists of four digits) (Series 1).
"21," "22," "23," or "24" denotes a Self-Aligning Spherical Roller Bearing (Series 3).
"N" denotes a Cylindrical Roller Bearing (including short cylindrical rollers and a subset of slender needle rollers) (Series 2).
"NU": Inner ring has no flanges.
"NJ": Inner ring has a single flange.
"NF": Outer ring has a single flange.
"N": Outer ring has no flanges.
"NN": Double-row cylindrical roller bearing; outer ring has no flanges.
"NNU": Double-row cylindrical roller bearing; inner ring has no flanges. (If the roller length is at least five times its diameter, it is classified as a Needle Roller Bearing) (Series 4).
"NA": Machined-ring Needle Roller Bearing (with outer ring).
"NK": Machined-ring Needle Roller Bearing (with outer ring).
"K": Needle Roller and Cage Assembly (without inner or outer rings).
"7" denotes an Angular Contact Ball Bearing (Series 6).
"3" denotes a Tapered Roller Bearing (Metric Series) (Series 7).
"51," "52," or "53" denotes a Thrust Ball Bearing (basic model consists of five digits) (Series 8).
"81" denotes a Thrust Cylindrical Roller Bearing (Series 9).
"29" denotes a Thrust Spherical Roller Bearing (Series 9).
National Standards for Bearings
GB/T 305-1998 Rolling Bearings -Retaining Slots and Retaining Rings on Outer Rings -Dimensions and Tolerances
GB/T 308-2002 Rolling Bearings - Steel Balls
GB/T 309-2000 Rolling Bearings -Needles
GB/T 4661-2002 Rolling Bearings -Cylindrical Rollers
GB/T 4662-2003 Rolling Bearings- Static Load Ratings
GB/T 6391-2003 Rolling Bearings- Dynamic Load Ratings and Rating Life
JB/T 3034-1993 Rolling Bearings -Rust-preventive Packaging with Oil-impregnated Paper
JB/T 3573-2004 Rolling Bearings - Methods for Measuring Radial Internal Clearance
JB/T 6639-2004 Rolling Bearing Components -Technical Specifications for Skeleton-type Nitrile Rubber Seals
JB/T 6641-2007 Rolling Bearings -Residual Magnetism and Its Evaluation Method
JB/T 6642-2004 Rolling Bearing Components - Methods for Measuring and Evaluating Roundness and Waviness Errors
JB/T 7048-2002 Rolling Bearing Components - Engineering Plastic Cages
JB/T 7050-2005 Rolling Bearings - Method for Evaluating Cleanliness
JB/T 7051-2006 Rolling Bearing Components - Methods for Measuring and Evaluating Surface Roughness
JB/T 7361-2007 Rolling Bearings - Methods for Hardness Testing of Components
JB/T 7752-2005 Rolling Bearings - Technical Specifications for Sealed Deep Groove Ball Bearings
JB/T 8196-1996 Rolling Bearings - Residual Magnetism of Rolling Elements and Its Evaluation Method
JB/T 8571-1997 Rolling Bearings -Sealed Deep Groove Ball Bearings - Test Procedures for Dust Prevention, Grease Leakage, and Temperature Rise Performance
JB/T 8921-1999 Rolling Bearings and Their Parts - Inspection Rules
JB-T 10336-2002 Rolling Bearings and Their Parts - Supplementary Technical Conditions
JB-T 50013-2000 Rolling Bearings - Life and Reliability Test Procedures
JB-T 50093-1997 Rolling Bearings -Life and Reliability Test Evaluation Methods
Prefix Code
The prefix symbol R is placed directly before the basic bearing designation, while all other symbols are separated from the basic designation by a dot.
GS: Thrust cylindrical roller bearing housing washer. Example: GS.81112
K: Rolling element and cage assembly. Example: Thrust cylindrical roller and cage assembly K.81108
R: Bearing without a separable inner or outer ring. Example: RNU207 (a NU207 bearing without an inner ring)
WS: Thrust cylindrical roller bearing shaft washer. Example: WS.81112
Bearing Suffix Code
Suffixes are placed after the basic designation. When multiple suffixes are present, they should be arranged from left to right in the specific order listed in the bearing designation tables. Certain suffixes are separated from the basic designation by a small dot.
Suffixes: Internal Structure
A, B, C, D, E: Variations in internal structure
Example: Angular contact ball bearings 7205C, 7205E, 7205B; C denotes a 15° contact angle, E denotes a 25° contact angle, and B denotes a 40° contact angle.
Example: Cylindrical roller, spherical roller, and spherical thrust roller bearings N309E, 21309E, 29412E; these feature a reinforced design with enhanced load-carrying capacity.
VH: Full-complement cylindrical roller bearings with self-retaining rollers (the nominal diameter of the rollers differs from that of standard bearings of the same model). Example: NJ2312VH.
Suffix-Bearing Boundary Dimensions and External Structure
DA: Separable double-row angular contact ball bearing with split inner rings. Example: 3306DA
DZ: Roller bearing with a cylindrical outer ring profile. Example: ST017DZ
K: Bearing with a tapered bore (taper ratio 1:12). Example: 2308K
K30: Bearing with a tapered bore (taper ratio 1:30). Example: 24040 K30
2LS: Double-row cylindrical roller bearing with a split inner ring and shields on both sides. Example: NNF5026VC.2LS
V: Modified internal structure; full-complement double-row cylindrical roller bearing with a split inner ring and shields on both sides.
N: Bearing with a snap ring groove in the outer ring. Example: 6207N
NR: Bearing with a snap ring groove and a snap ring in the outer ring. Example: 6207 NR
N2: Four-point contact ball bearing with two snap ring grooves in the outer ring. Example: QJ315N2
S: Bearing with a lubrication groove and three lubrication holes in the outer ring. Example: 23040S. (Note: Spherical roller bearings with an outer diameter D ≥ 320 mm are not designated with the suffix S.)
X: External dimensions conform to international standards. Example: 32036X
Z••: Technical specifications for special internal structures. Designations are arranged sequentially starting from Z11. Example: Z15 (Stainless steel bearing; W-N01.3541). ZZ: Roller bearing with two guiding flanges on the outer ring (suffix).
Bearing Suffix Codes (Sealing and Dust Protection)
RSR bearings feature a seal on one side. Example: 6207 RSR.
2RSR bearings feature seals on both sides. Example: 6207.2RSR.
ZR bearings feature a dust shield on one side. Example: 6207 ZR.
2ZR bearings feature dust shields on both sides. Example: 6207.2ZR.
ZRN bearings feature a dust shield on one side and a snap ring groove on the outer ring on the other side. Example: 6207 ZRN.
2ZRN bearings feature dust shields on both sides and a snap ring groove on the outer ring. Example: 6207.2ZRN.
Bearing Suffix (Cage and Material)
Solid cage designation A or B is placed after the cage code:
A indicates that the cage is outer-ring guided;
B indicates that the cage is inner-ring guided.
F: Solid steel cage, rolling-element guided.
FA: Solid steel cage, outer-ring guided.
FAS: Solid steel cage, outer-ring guided, with lubrication grooves.
FB: Solid steel cage, inner-ring guided.
FBS: Solid steel cage, inner-ring guided, with lubrication grooves.
FH: Solid steel cage, carburized and hardened.
H, H1: Carburized and hardened cage.
FP: Solid steel window-type cage.
FPA: Solid steel window-type cage, outer-ring guided.
FPB: Solid steel window-type cage, inner-ring guided.
FV, FV1: Solid steel window-type cage, aged and tempered.
L: Solid light-metal cage, rolling-element guided.
LA: Solid light-metal cage, outer-ring guided.
LAS: Solid light-metal cage, outer-ring guided, with lubrication grooves.
LB: Solid light-metal cage, inner-ring guided.
LBS: Solid light-metal cage, inner-ring guided, with lubrication grooves.
LP: Solid light-metal window-type cage.
LPA: Solid light-metal window-type cage, outer-ring guided.
LPB: Solid light-metal window-type cage, inner-ring guided (shaft-guided for thrust roller bearings).
M, M1: Solid brass cage
MA: Solid brass cage, outer ring guided
MAS: Solid brass cage, outer ring guided, with lubrication grooves
MB: Solid brass cage, inner ring guided (for spherical roller thrust bearings, shaft ring guided)
MBS: Solid brass cage, inner ring guided, with lubrication grooves
MP: Solid brass cage with straight pockets
MPA: Solid brass cage with straight pockets, outer ring guided
MPB: Solid brass cage with straight pockets, inner ring guided
T: Solid phenolic laminated fabric cage, rolling element guided
TA: Solid phenolic laminated fabric cage, outer ring guided
TB: Solid phenolic laminated fabric cage, inner ring guided
THB: Phenolic laminated fabric cage with pockets, inner ring guided
TP: Solid phenolic laminated fabric cage with straight pockets
TPA: Solid phenolic laminated fabric cage with straight pockets, outer ring guided
TPB: Solid phenolic laminated fabric cage with straight pockets, inner ring guided
TN: Molded engineering plastic cage, rolling element guided (additional digits indicate different materials)
TNH: Molded engineering plastic cage with self-locking pockets
TV: Solid glass fiber reinforced polyamide cage, ball guided
TVH: Solid glass fiber reinforced polyamide cage with self-locking pockets, ball guided
TVP: Solid glass fiber reinforced polyamide cage with window-type pockets, ball guided
TVP2: Solid glass fiber reinforced polyamide cage, roller guided
TVPB: Solid glass fiber reinforced polyamide cage, inner ring guided (for roller thrust bearings, shaft guided)
TVPB1: Solid glass fiber reinforced polyamide cage with window-type pockets, shaft guided (for roller thrust bearings)
Stamped Cage
J: Stamped steel cage
JN: Riveted cage for deep groove ball bearings
Cage Modifications
Numbers appended to the end of-or inserted within-a cage designation indicate that the cage structure has undergone modification. These numbers are used only during transitional periods; e.g., NU1008M 1.
Suffixes: Bearings Without Cages
V: Full-complement bearing (without cage); e.g., NU 207VV
T: Full-complement bearing with separating balls or rollers; e.g., 51120VT
Suffixes: Tolerance Class (Dimensional Accuracy and Rotational Accuracy)
P0: Tolerance class conforming to ISO Class 0; omitted from the designation (not explicitly indicated)
P6: Tolerance class conforming to ISO Class 6
P6X: Tolerance class conforming to ISO Class 6 (for tapered roller bearings)
P5: Tolerance class conforming to ISO Class 5
P4: Tolerance class conforming to ISO Class 4
P2: Tolerance class conforming to ISO Class 2 (excluding tapered roller bearings)
SP: Dimensional accuracy equivalent to Class 5; rotational accuracy equivalent to Class 4 (for double-row cylindrical roller bearings)
UP: Dimensional accuracy equivalent to Class 4; rotational accuracy superior to Class 4 (for double-row cylindrical roller bearings)
HG: Dimensional accuracy equivalent to Class 4; rotational accuracy superior to Class 4 but inferior to Class 2 (for spindle bearings)
Bearing Suffix - Clearance
C1 Clearance: Conforms to Group 1 as specified by the standard; smaller than Group 2.
C2 Clearance: Conforms to Group 2 as specified by the standard; smaller than Group 0.
C0 Clearance: Conforms to Group 0 as specified by the standard; omitted from the designation and not explicitly indicated.
C3 Clearance: Conforms to Group 3 as specified by the standard; larger than Group 0.
C4 Clearance: Conforms to Group 4 as specified by the standard; larger than Group 3.
C5 Clearance: Conforms to Group 5 as specified by the standard; larger than Group 4.
When both the tolerance class code and the clearance code need to be indicated simultaneously, they are combined by appending the clearance group number (omitting Group 0) to the tolerance class code (omitting Class P0).
Example: P63 = P6 + C3; indicates a bearing tolerance class of P6 and a radial clearance of Group 3.
P52 = P5 + C2; indicates a bearing tolerance class of P5 and a radial clearance of Group 2.
Non-standard Clearance: In cases requiring specific radial or axial clearance values, the relevant limit values should be indicated in micrometers (μm) following the letter R (for radial clearance) or A (for axial clearance), with the numerical values separated by a decimal point.
Example: 6210.R10.20 - Bearing model 6210 with a radial clearance of 10 μm to 20 μm.
6212.A120.160 - Bearing model 6212 with an axial clearance of 120 μm to 160 μm.
