ABEC Tolerances


Pacamor Kubar Bearings - PKB

Grades of Precision

BEARINGS are manufactured to standard grades of precision with established tolerances for size and geometric accuracy. These standards are known as ABEC classes as set by the Annular Bearing Engineers Committee of the American Bearing Manufacturer's Association (ABMA). These standards are also accepted by (ANSI) American National Standards Institute and by international agreement for the standards developed by (ISO) International Organization of Standardization.

The ABEC scale is a system of rating the manufacturing tolerance of precision bearings. The system was developed by the Annular Bearing Engineering Council (ABEC), a division of the American Bearing Manufacturers' Association ABMA). The ABMA was formerly known as the Anti-Friction Bearing Manufacturers' Association. Bearings rated under the ABEC systems are typically called "precision bearings", with a rating or class from 1 to 9. ABEC 1 meets a looser tolerance and ABEC 9 meets high precision tight bearing tolerances. ABEC class is not to be confused with radial play, which is discussed further down.

ABEC Tolerances
All tolerances are in .0001 inches abec 1 abec 3p abec 5p abec 7p abec 9p
INNER RING (Bore Diameter < 0.7087 inches)  
Bore Tolerance +0/-3 +0/-2 +0/-2 +0/-2 +0/-2
Radial Runout (Bore 0 - 0.3937") 3 2 1.5 1 0.5
Radial Runout (Bore 0.3937 - 0.7087") 4 3 1.5 1 0.5
Width Tolerance +0/-50 +0/-50 +0/-10 +0/-10 +0/-10
Width Variation - - 2 1 0.5
Reference Runout with Bore (max) - - 3 1 0.5
Groove Runout with Reference Side (max) - - 3 1 0.5
Bore 2 Point Out of Round (max) - - 1 1 0.5
Bore Taper (max) - - 1 1 0.5
OUTER RING (OUTER Diameter < 0.875 inches)  
Outer Diameter Tolerance +0/-3 +0/-3 +0/-2 +0/-2 +0/-1
Radial Runout (max) 6 4 2 1.5 0.5*
Width Tolerance +0/-50 +0/-50 +0/-10 +0/-10 +0/-10
Width Variation - - 2 1 0.5
Flange Width Tolerance Limits - +0/-20 +0/-20 +0/-20 -
Flange Diameter Tolerance Limits - +50/-20 +0/-10 +0/-10 -
Groove Runout with Reference Side (max) - - 3 2 0.5*
Outside Cylindrical Surface
Runout with Reference Side (max)
- - 3 1.5 0.5


* For ABEC 9 Bearings with Outer Diameters from 0.787 to 0.875
O.D tolerance = +0 / -1.5
Radial Runout = 1
Groove Runout with Reference Side = 1



Radial Play

Bearing Radial Play

Bearing radial play is a function of radial movement of the inner ring in relation to the outer ring. It is usually measured by holding the inner ring stationary and applying a radial load to the outer. Ball bearings are assembled with a slight amount of space between the balls and the raceways. This space represents the Radial Play. Radial play affects the performance in a given application by allowing the bearing to rotate smoothly with a predicable level of play. Radial Play is a result of the bearing's internal geometry. Therefore, the Radial Play value is a result of manufacturing tolerances. Radial play is measured perpendicular to the bearing's axis of rotation while the bearing is unmounted from the final assembly. When properly measured, the radial play measurement yields the maximum displacement that one bearing ring can be located relative to the other. Generally, the inner ring is held in place on a shaft and the outer ring is moved radially for evaluation. Operating conditions must be considered when specifying Radial Play. Such factors as heat and lubrication can have a dramatic effect on Radial Play during bearing operation in the field.

Specified radial play should not be impeded, as this has an adverse effect on bearing life. The fit of the bearing on the shaft or in the housing will also impact bearing life. When the radial play is pushed below its specified level, discreet bearing components can become overheated, especially under extremely high running torque conditions. When the components become hot, the bearing retainer can cause catastrophic failure of the bearing. If that doesn't happen, the retainer still may heat up enough to melt or become deformed. Then the retainer may rub on the bearing rings and begin flaking apart, causing debris and contamination to fall into the bearing components and result in premature bearing failure.


ABMA Standard Values for Radial Play
Clearance Type Range Designation
Tight.0001 inch to .0003 inch K13
Normal.0002 inch to .0005 inch K25
Loose.0005 inch to .0008 inch K58
Extra Loose.0008 inch to .0011 inch K811

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.


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   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 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 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-6085 GP = 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 Pairing DT = Tandem Pairing
DF = Face to Face Pairing DU = 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