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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
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 loadF r
Axial loadF 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 sealsShields Low-friction
sealsSeals
-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 setElastic deformation due to load
Double Row Angular Contact Ball Bearing
Ball bearing propertiesDeep grooveball bearing
Angular contactball bearing
Self-aligning ball bearing
radial loadcarrying capacity
axial loadcarrying capacity
speedcapability
can accommodatemisalignment
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 BearingsCARBTM
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 BearingsCARBTM
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 m 0/-12 m 0/-9 m 0/-7 m0/-2,5 m
How much is a m
1
0,06 mm
A human
hair
Materials for rolling bearingsBearing 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 steel
appr. 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