ubc guide to bearings

7/30/2019 UBC Guide to Bearings

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UBC Bearin s of America Limited


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basic

BEARING

knowledge


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What is a Bearing Used for?

Designed to:

lReduce frictionl

Carry loadslGuide moving parts


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Rolling and Sliding Friction


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Component parts of a ball bearing

Seal Rolling elements Inner ringOuter ring Cage Seal


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Shields Low-friction seals Seals

-Z and -2Z -RZ and -2RZ -RS and -2RS

Contaminantexclusion

Silentrunning

Greaseretention

Speedcapability

SealandShield

Variations


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Application Shield Seal

Need 2Z 2RZ 2RS

Low friction +++ ++(+)

torque

High speed +++ ++(+)

abilityGrease + ++ +++

retention

Dust + ++ +++

exclusion

Water +

exclusion

Low/high Depends on: Depends on:

operatingtemperature Grease Grease

Rubber mix

+++ Excellent ++ Good + Fair Poor

Characteristics of Different Seals


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Storage Requirements


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Roller and Ball Raceway Contact


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Axial and Radial load capability

Axial load

Radial loadCombined load

Fa

Fr


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Roller Types

Spherical roller(asymmetrical)

Taper roller

Spherical roller(symmetrical)

Needle roller

Cylindrical roller

Ball


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Ball and Roller Bearing Ranges

Deep groove

Ball bearings Roller bearings+Angularcontact

Self-aligning Cylindrical Taper Spherical


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Load Capabilities

Load carrying capacityis expressed as the basicdynamic load rating


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Ball Bearing Capabilities

Deep groove Angular contact Self-aligning

Radial load Axial load Speed Accommodates

carrying capacity carrying capacity capability misalignment


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Function of the Cage

Prevent immediate contact betweenrolling elements to minimize frictionand heat generation

Guide the rolling elements

Provide space for lubricant

Retain the rolling elements when

bearings of separable designare mounted or dismounted


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Cage Variants

Nylon cage Steel cage Solid brass cage


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Nylon Cages

+ Lightweight

+ High elasticity

+ Good sliding properties

+ Good marginallubrication properties

Operating temperature< +120 C


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Steel Cages

+ Lightweight

+ High strength

+ High vibration andacceleration resistance

Sensitive topoor lubrication

+ No operatingtemperature limit


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Solid Brass Cages

+ Very high strength

+Suitable for very highspeed in connectionwith circulating oil

Relatively (very)expensive

+ Very high vibration andacceleration resistance


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Internal Clearances

Radialclearance

Axialclearance


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The bearing internal clearance is defined

as the total distance through which onebearing ring can be moved relative to the

other under zero measuring load.


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Why Internal clearance?

In order to fit a bearing tightly on a shaft, it is necessary

that the shaft is slightly larger than the bore of the inner

ring. When the bearing is mounted, the inner ring willbe expanded and consequently the space available for

the rolling elements will be reduced. The reduction in

space available for rolling elements when the bearing ismounted is accommodated by the internal clearance.


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Why Internal clearance?

Steel will expand with increased temperature. In

operation, the temperature of the various parts of abearing will not remain uniform and resulting in

varying degrees of expansion which is compensated

by the internal clearance.


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Internal Radial Clearance

Clearance range

C1 Clearance less than C2

C2 Clearance less than Normal

C3 Clearance greater than Normal

C4 Clearance greater than C3

C5 Clearance greater than C4

COLD

WARM

Reducedradial

clearance

Expansion

Compression


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The internal clearance required is

dependent upon the mounting fit and

the operating conditions. In case of

doubt, a bearing with greater internal

clearance shall always be selected.


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Effect of Internal Preload and Clearance on

Bearing LifeRelative basic rating life L10, %

Preloading Clearance


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Correct Fits

Tolerance range for bearings

manufactured to ISO


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Operating conditions

Available space Misalignment

Speed Life

Load/Direction

Bearing Selection Factors


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International

Organization forStandardization

ISO

ISO Standards


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Diameter Series


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Relationship: Diameter and Width Series

Diameter Series

Width Series Height Series


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Dimension Series

Width Series

Dia

meterSeries


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Bore diameterWritten as Example

Below 10 mm

3

.

.

9

3

.

.

9

623

.

.

629

10 17 mm

10

12

15

17

00

01

02

03

6200

6201

6202

6203

20 480 mm

20

25

.

.

480

04

05

.

.

96

6204

6205

.

.

61896

Above 500 mm 710 /710 241/710

Bore designation system


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How the Designation System Works

Bearing types

Radial bearings, width (B, T) Thrust bearing, height (H)

Outside diameter (D)

Bearing size d/5

(30 mm bore diameter)


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Tapered Bore Suffixes

Suffix K

Suffix K30

Taper 1:12

Taper 1:30


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Deep

grooveb

allbearin

g


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Self-a

ligningb

allbearin

g


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Planethrustb

allbearin

g


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Angula

rcontact

ballbearing


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Sphe

ricalrolle

rbearing


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Tap

erroller

bearing


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Cylindricalrollerbearin

g


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THE END

ubc guide to bearings

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