PKB Ball Bearing Nomenclature


PACAMOR KUBAR BEARINGS offers an array 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 bearing application, dissimilar materials can prevent component microwelding and extend the life of the bearing.

To this end, we offer standard stainless steel or optional ceramic balls or titanium carbide-coated 440C stainless steel balls(Tic), in our miniature bearing designs.

PACAMOR KUBAR BEARINGS precision miniature bearings are available with up-to ABEC 9 tolerances (as defined by the American Bearing Manufacturers’ Association), with an optional flanged outer rings.


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
  S (ZZ) R PH 144 Z


Special Feature 

X followed by two numbers = Special feature or change in standard dimension, to basic bearing number.

A = Tapered Outside Diameter (OD)



S = AISI44OC stainless steel



F = Flanged bearing No Symbol = straight OD

(ZZ) = Open bearing, but with shielded width   



R = Radial Inch

Blank or MM = Metric

AINS = Angular Contact Inner-Relieved, Non-Separable

AIS = Angular Contact Inner-Relieved, Separable

AONS = Angular Contact Outer-Relieved, Non-Separable

AOS = Angular Contact Outer-Relieved, Separable


Retainer Type

Standard retainer could be either one piece crown or two piece ribbon type.

Blank = Pacamor’s standard option

B = Two Piece Ribbon

PH = Phenolic Crown Retainer 

F = Full-Complement (No Retainer)

SL = Slug Separators

TO = Teflon Toroids



*Other machined retainer options available


Basic Size (Bearing Chassis)

See basic bearing numbers listed in our catalog



Z = Single shield LL = Double glass-reinforced Teflon seal
ZZ = Double shield RS = Single rubber seal
Z1 = Shield on flanged side 2RS = Double rubber seal
Z2 = Shield opposite flanged side V = Single non-contact seal
T = Single Teflon seal VV = Double non-contact seal
TT = Double Teflon seal UZ = Single shielded, narrow width bearings
L = Single glass-reinforced Teflon seal  — No designation = open bearing.


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


Ring Feature 

EE = Extended inner rings 
NR = Snap ring on bearing OD
Blank = 440c Stainless Steel Balls


Alternate Ball Material

CB = Ceramic (Silicon Nitride) balls

TiC = TiC-coated 440c stainless steel balls


Radial Play 

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 

A1 = ABEC 1
A3 = ABEC 3
A5 = ABEC 5P
A7 = ABEC 7P
A9 = ABEC 9P*

*ABEC9 tolerances are available upon request


Functional Test  

Blank = Pacamor’s standard option

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



Blank = Pacamor’s standard option

See our common lube codes here

LD = Dry bearings (no lubrication)
GP = Indicates grease plate  
BC = Indicates barrier coating  
OP = Oil plate
DIC = Dicronite coating

Alternate lubes/coatings available upon request.



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 (also known as Duplex Sets or Duplex Pairs)

DB = Back to Back Pairing   — DT = Tandem Pairing
DF = Face to Face Pairing   — DU = Universal Pairing



The following symbols indicate various types available:            

Blank = Vial packaging
P = Individual pill packaging
B symbol = Individual box
M symbol = Individual pack per Mil-197


Contact PKB for more offerings.