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ISO 9001:2000 Certified Quality Management System

Ball Bearing Nomenclature

Ball Bearing Part Numbering System and Methodology

PACAMOR KUBAR BEARINGS offers a range of retainer designs and materials including, but not limited to Crown, Ribbon, heat and moisture resistant Phenolic, and Torlon (polyamide-imide). In addition to selecting the right retainer for your miniature and instrument bearing application, dissimilar materials can prevent component welding and extend the life of the bearing in a variety of applications.

To this end, we offer standard 400C stainless steel or optional ceramic balls or titanium carbide coated 440C stainless steel balls in our miniature and instrument bearing designs.

PACAMOR KUBAR BEARINGS precision miniature and instrument bearings are available with up to ABEC 9 tolerances (as defined by the American Bearing Manufacturers' Association) with an optional flanged outer ring.

For further assistance with bearing selection and design, please feel free to contact our engineering team or look at our online catalog .

Description of
PACAMOR KUBAR BEARINGS part numbering system and methodology for identifying a PKB part number.


Special Feature Material Type Style Retainer Basic Size Closure
X S F R B 2-5 ZZ
R PH 144 Z


Special Feature

X = special feature or change in standard dimension to basic bearing number
A = tapered O.D.


S = AISI44OC stainless steel

Type (F)

F = flanged bearing No Symbol = straight O.D.

Style (R)

R symbol is to be used for all miniature and instrument bearings to signify single row.

Retainer (B, PH) - When blank, manufacturer standard or option.

Standard retainer could be either one piece crown or two piece ribbon type. When Blank = manufacturer's standard B = Two Piece Ribbon PH = Phenolic Crown Retainer

Basic Size (2-5, 144)

See basic bearing numbers listed

Closures (ZZ,Z)

Z = Single shieldLL = Double glass-reinforced Teflon seal
ZZ = Double shieldRS = Single rubber seal
Z1 = Shield on flanged side2RS = Double rubber seal
Z2 = Shield opposite flanged sideV = Single non contact seal
T = Single Teflon sealVV = Double non contact seal
TT = Double Teflon sealUZ = Single shielded narrow width bearings
L = Single glass-reinforced Teflon sealNo designation = open bearing.


Ring Feature Radial Play ABEC Tolerance Functional Test Lubrication Coding / Duplex Package
EE K25 A5 ST10 L245X ZD P
  K24 A7 EMQ ROY27 DB B


Ring Feature (EE,NR)

EE = extended inner rings
NR = snap ring on bearing O.D.

Radial Play (K25,K24)

Symbol K followed by number indicates radial play in tenths of thousands of an inch.
K25 = 0.0002 to 0.0005
K58 = 0.0005 to 0.0008

ABEC Tolerances (A5, A7)

A1 = ABEC 1
A3 = ABEC 3
A5 = ABEC 5P
A7 = ABEC 7P
A9 = ABEC 9P
Selected ABEC9 tolerances are available upon request

Functional Test (ST10,EMQ) - When blank, manufacturer standard.

ST followed by number indicates starting torque in hundreds of MG-MM
E.M.Q. = Electric Motor Quality

Lubrication (L245X,ROY27) - When blank, manufacturer option.

LD = Dry bearings / no lubrication
Standard Oil L245X, MIL-L-6085GP = Indicates grease plate
Standard Grease ROYCO27, MIL-G-23827 BC = Indicates barrier coating
Alternate lubes available upon request.


Coding (ZD)

Tolerance 0.0001 Increment Coding (Standard), In 0.000050 Increment Coding, In
Nominal to -0.000050, In 1 A
-0.000050 to -0.000100, In B
-0.000100 to -0.000150, In 2 C
-0.000150 to -0.000200, In D
-0.000200 to -0.000250, In 3 E
-0.000250 to -0.000300, In F
Grade Symbols
Graded Bore and OD ZD XZD
Graded Bore Only ZB XZB
Graded OD Only ZO XZO


Duplex Coding (DB)

DB = Back to Back PairingDT = Tandem Pairing
DF = Face to Face PairingDU = Universal Pairing


Packaging (P,B)

The following symbols indicate various types available:
Blank = Vial packaging
P = Individual pill packaging
B symbol = Individual box
M symbol = Individual pack per mil-p-197