Bearing Basics

An introduction to SKF bearing technology

Bearings are machine elements

Bearings are designed to

reduce friction carry loads guide moving parts

What is Friction ?

Friction is resistance to movement

it opposes sliding it assists rotation

What is friction?Plain bearingssliding friction

Rolling bearingsrolling friction

µ

µ

How did a bearing evolve ?Bearing history - a never-ending story

1100 B.C.

3500 B.C.1995

1794

40 A.D.

1869

How did a bearing evolve ?

How did a bearing evolve ?

* Invention of wheel

* Wheel rotates on axle

* Wear Plate + Rollers

* Inner ring + Outer ring

+ Rollers

* With introduction of

cage Rolling Bearing

was created

The components of a bearing

Seal Rolling elements Inner ringOuter ring SealCage

Pg. 7 Bearing Installation and Maintenance Guide

Bearing Basics

POINT CONTACT

LINE CONTACT LINE CONTACT

BALL SPHERICAL TAPERED

Bearing Basics

Characteristics

Deep grooveball bearing

Angular contactball bearing

Self-aligningball bearing

Ball bearings Point Contact :

* Less area of contact* Less friction* More speed * Less load

Cylindricalrollerbearing

Taperrollerbearing

Needlerollerbearing

Sphericalroller bearing

Roller bearingsLine Contact :

* More area of contact* More friction* Less speed * More load

Rolling elements name the bearing

Spherical roller(symmetrical)

Ball Spherical roller(asymmetrical)

Needle roller

Cylindrical roller Taper roller

Bearing loads

Radial load

F r

Axial load

F a

Combinedload

Radial rolling bearings

Deep grooveball bearing

Angular contactball bearing

Self-aligningball bearing

Cylindricalrollerbearing

Taperrollerbearing

Needlerollerbearing

Sphericalroller bearing

Ball bearings Roller bearings

Radial rolling bearings

Thrust ball bearing

Ball bearings Roller bearings

Thrust bearings

Angular Contact Ball Thrust bearing

Taper Roller Thrust bearing

Spherical Roller Thrust bearing

Cylindrical / Needle Roller Thrust bearing

Deep Groove Ball Bearing

Bearings with shields and seals

Shields Low-frictionseals

Seals

-Z and -2Z -RZ and -2RZ -RS1 and -2RS1

Contaminantexclusion

Silentrunning

Greaseretention

Speedcapability

Misalignmentsproduce additional stressesshorten bearing lifeincrease seal wearincrease vibrationincrease noiseincrease energy consumption

which will be avoided by proper shaft alignment or the use of a self-aligning bearing

MisalignmentParallel or offset misalignment Angular misalignment

The industrial revolution has depended on a seldom recognized

component, the rolling bearing. So important is the rolling bearing that

without it today's modern industry would literally grind to a halt. From the

beginning, SKF has led the world in reducing friction with innovative rolling

bearing solutions that have moved industry forward.

SKF was founded in Sweden in 1907 and grew out of Sven

Wingquist's solution to a misaligned drive shaft problem he faced in a textile mill. His invention of a double row self-

aligning ball bearing was only the first of many innovations SKF has provided

industry. From the first spherical rolling bearing to the current bearing life

calculation methods used worldwide, SKF has pioneered the way with over

2,200 patents.

Self Aligning Ball Bearing

Bearing Basics

Paired mounting increases load carrying capacity and stiffness of the bearing arrangement

Face-to-facearrangemente.g. 71906/DF

Back-to-backarrangemente.g. 71906/DB

Tandemarrangemente.g. 71906/DT

Bearing stiffness (N/mm) =Force acting on bearing or set

Elastic deformation due to load

Double Row Angular Contact Ball Bearing

Ball bearing propertiesDeep grooveball bearing

Angular contactball bearing

Self-aligning ball bearing

radial load

carrying capacity

axial load

carrying capacity

speedcapability

can accommodate

misalignment

Bearing Basics

Cylindrical roller bearings

More and larger rollers

Logarithmic contact profile plus optimised surface finish

Improved roller end/flange contact geometry

3 cage variants: steel, polyamide, brass

NU NUPNJ

N NJ+HJNU+HJ

Bearing Basics

Bearing Basics

Bearing Basics

Spherical roller bearings

Symmetrical rollersfor maximum life underany conditions

Floating guide ringgives minimum frictionand ensures reliableoperation

Window-type steel cagesstrong and tolerant tohigh temperatures

Taper rollersfor perfect rolling contact

Specially designed flange gives minimum friction and ensures reliable operation

Window-type steel cages strong and tolerant to high temperatures

Logarithmic profiled rollers for protection from edge loading

Taper roller bearings

Single row and paired single rowtaper roller bearings

Single row Face-to-facearrangement

suffix DF

Back-to-backarrangement

suffix DB

Compact Aligning Roller BearingsCARB

TM

Safer, more optimized design Increased service life

Lower running temperatureLower vibration and noise levelExtended maintenance interval

Higher axial clearenceNo internal Friction force

Longer lifeHigher speedDownsizing possibility

CARB - BearingTM

Compact Aligning Roller Bearing

Self-aligning as spherical roller bearing

Permits axial displacements like a cylindrical roller bearing

Compact as a needle roller bearing

Thrust bearingsThrust ball bearing

single directionThrust ball bearing

single direction withsphered housing washer

Thrust ball bearingdouble direction

Thrust ball bearingdouble direction with

sphered housing washers

Cylindrical rollerthrust bearing

single direction

Spherical rollerthrust bearing

Combined load carrying capacity Can take 55% of thrust load as radial load

Specially designed flange gives minimum friction and ensures reliable operation

Window-type steel cages strong and tolerant to high

temperatures

Logarithmic profiled rollers for protection from edge loading

Spherical roller thrust bearings

Compact Aligning Roller BearingsCARB

TM

Safer, more optimized design Increased service life

Lower running temperatureLower vibration and noise levelExtended maintenance interval

Higher axial clearenceNo internal Friction force

Longer lifeHigher speedDownsizing possibility

Bearings are precision products

Example:Tolerances forbore diameter

75 mm

Precisionbearing

High precisionbearing

Normal

Toleranceclasses

Standard P6 P5SP

P4AUP

PA9APA9B

0/-15 µm 0/-12 µm 0/-9 µm 0/-7 µm0/-2,5 µm

How much is a µm

1 µ

0,06 mm

A human

hair

Materials for rolling bearings

Bearing rings and rolling elements

1. Through-hardening steels

Carbon chromium steel containing approximately

1 % carbon and 1,5 % chromium

2. Case-hardening steels

– Chromium-nickel alloyed steel

– Manganese-chromium alloyed steelappr. 0,20 % carbon

SKF bearing steels have very high cleanliness – the content of macro and microinclusions is extremely low.

Cages keep the rolling elements separated

Prevent immediate contact between rolling elements to minimise friction and heat generation

Guide the rolling elements

Provide space for lubricant

Serve to retain the rolling elements when bearings of separable design are mounted or dismounted

Polyamide cagelightweighthigh elasticitygood sliding propertiesgood marginal lubricationpropertiesoperating temperaturelimit +120°C

Window-type steel cagelightweighthigh strengthno operating temperature limithigh vibration and acceleration resistancesensitive to poorlubrication

Window-type brass cagevery high strengthvery high vibration andacceleration resistancesuitable for very highspeeds in connection withcirculating oil lubricationrelatively expensive

Cage variants

++++

-

+++

+

-

++

+

-

Bearing clearance

Radialclearance

Axial clearance

ClearanceNormal clearance Increased clearance

because of temperatureReduced clearancebecause of tight fit

Example:6210/C3 = Deep groove ball bearing withclearance greater than Normal

CN does not normally appear in the bearing designation

clearanceless than C2less than NormalNormalgreater than Normalgreater than C3greater than C4

Suffix/C1/C2/CN/C3/C4/C5