FAG Rolling Bearings: Fundamentals, Types, …

1 Rolling BearingsTechnical InformationTI No. WL 43-1190 EAOctober 1999 FAG Rolling BearingsFundamentals types DesignsFAG2 Contents IntroductionContentsThe FAG Rolling bearing programme ..3 Rolling bearing types ..4 Rolling bearing components ..5 Rolling elements ..5 bearing rings ..6 Cages ..6 Load ratings ..8 Combined load ..8 Dimensioning ..9 Statically stressed bearings ..9 Service life ..9 Wear ..9 Dynamically stressed bearings .. 10 Nominal rating life .. 11 Adjusted rating life calculation .. 12 Lubrication .. 17 Grease lubrication .. 17 Oil lubrication .. 17 Important Rolling bearing lubrication terms .. 17 Seals .. 21 Speed suitability .. 22 High temperature suitability .. 23 bearing clearance .. 24 Tolerances .. 26 Alignment .. 27 Fits .. 28 bearing arrangement .. 29 Symbols for load carrying capacity, alignmentand speed suitability .. 32 Deep groove ball bearings.

2 33 Angular contact ball bearings, single row .. 34 Angular contact ball bearings, double row .. 35 Four-point bearings .. 36 Self-aligning ball bearings .. 37 Cylindrical roller bearings .. 38 Tapered roller bearings .. 40 Barrel roller bearings .. 42 Spherical roller bearings .. 43 Thrust ball bearings .. 45 Angular contact thrust ball bearings .. 46 Cylindrical roller thrust bearings .. 47 Spherical roller thrust bearings .. 48 Matched Rolling bearings .. 49 bearing units .. 50 Checklist for Rolling bearing determination .. 52 Index .. 53 IntroductionThis Technical Information contains a summary of funda-mental knowledge of FAG Rolling bearings and should serve asan introduction to Rolling bearing engineering. It is intendedfor those who have little or no knowledge of Rolling you should like to enlarge your fundamental knowledge atyour PC, we recommend you to use our Rolling bearing learn-ing system (cp.)

3 Also Publ. No. WL 00106).The FAG catalogue WL 41520 "FAG Rolling Bearings" is frequently referred to in this publication. It provides all the essential data designers need to safely and economically designall standard Rolling FAG Rolling bearing catalogue on CD-ROMoutshinesthe usual software catalogues, being a comfortable, electronicconsulting system. In a dialogue with WINDOWS you canquickly select the right FAG Rolling bearing for your applica-tion and accurately calculate its life, speed, friction, tempera-ture and cycling frequencies. This will save you a lot of moneyand large number of technical publications is available for spe-cific applications which you can order from us indicating thepublication bearing codes are explained in detail in our TechnicalInformation WL Rolling bearing engineering terms appear in boldface andwill be explained in more detail (see also index at the end ofthis TI).3 FAGThe FAG Rolling bearing programmeThe FAG Rolling bearing programmeThe FAG Rolling bearing programme offers Rolling bearingswithin outside diameters ranging from 3 millimetres to metres, housings and accessories.

4 The catalogue WL 41 520 FAG Rolling Bearings contains excerpts fromthis programme for the industrial original equipment manu-facture (OEM), distribution, and replacement demand. Withthe products from this catalogue, most of which are producedin series, almost any application problem can be solved. To en-sure quick availability of Rolling bearings, housings and acces-sories, our stock-keeping programmes are constantly adaptedto the requirements in your standardized Rolling bearing programmeIn the catalogue WL 41 520, priority is given to Rolling bear-ings in DIN/ISO dimensions. This allows the designer to solve almost any application problem quickly and target industry programmesFAG have compiled special programmes for certain branchesof industry. In addition to the standardized Rolling bearings,these programmes contain numerous special designs which offer efficient, cost-effective solutions for more complicatedbearing cylindrical roller bearing for Rolling mills (upper)Self-aligning cylindrical roller bearings for paper-makingmachines (middle)FAG standardized Rolling bearings, housings and accessories(lower)FAG4 Rolling bearing typesRolling bearing typesNumerous Rolling bearing types with standardized main di-mensions are available for the various bearings are differentiated according to: the direction of main load: radial bearingsand thrust bearings have a nominal contact angle 0of 0 to 45.

5 Thrust bearings have a nominal contactangle 0of over 45 to 90 . the type of Rolling elements:ball bearingsand roller essential differences between ball bearings and roller bear-ings are: Ball bearings: lower load carrying capacity, higher speeds Roller bearings: higher load carrying capacity, lower speedsOther distinctive characteristics: separableor non-separable axial displaceability of the bearing rings relative to eachother (ideal floating bearings) self-aligning capabilityof the bearingContact angleThe Rolling elementstransmit loads from onebearing ringtothe other in the direction of the contact contactangle is the angle formed by the contact lines and the radialplane of the bearing . 0refers to the nominal contact angle, the contact angle of the load-free bearing . Under axial loads the contact angle of deep groove ball bearings, angularcontact ball bearings etc. increases. Under a combined loaditchanges from one Rolling elementto the next. These changingcontact angles are taken into account when calculating thepressure distribution within the bearings and roller bearingswith symmetrical Rolling ele-ments have identical contact angles at their inner rings andouter rings.

6 In roller bearings with asymmetrical rollers thecontact angles at the inner rings and outer rings are not identi-cal. The equilibrium of forces in these bearings is maintainedby a force component which is directed towards the cone apexThe pressure cone apex is that point on the bearing axis wherethe contact linesof an angular contact bearing , an angularcontact ball bearing , a tapered roller bearing or a spherical roller thrust bearing , intersect. The contact linesare the gener-atrices of the pressure cone angular contact bearingsthe external forces F act, not at thebearing centre, but at the pressure cone apex. This fact has tobe taken into account when calculating the equivalent dynamicloadP and the equivalent static ball bearingsRadial roller bearingsThrust ball bearingsThrust roller bearingsDeep grooveball bearingAngular contact ball bearingsingle rowFour-pointbearingSelf-aligningball bearingdouble rowCylindricalrollerbearingNeedle rollerbearingTaperedrollerbearingBarrelr ollerbearingSphericalrollerbearingThrust ball bearingAngular contact thrustball bearingdouble directionCylindrical roller thrust bearingSpherical roller thrust bearing 5 FAGR olling bearing componentsRolling elementsRolling bearing componentsRolling bearings generally consist of bearing rings(inner ringand outer ring), Rolling elementswhich roll on the raceways ofthe rings, and a cagewhich surrounds the Rolling Outer ring, 2 Inner ring, 3 Rolling element, 4 CageThe lubricant (usually lubricating grease orlubricating oil)

7 Alsohas to be regarded as a Rolling bearing component as a bearingcan hardly operate without a lubricant. Sealsare also increas-ingly being integrated into the material of which rings and Rolling elements for FAG Rolling bearings are made is normally a low-alloyed, through-hardening chromium steel which is identified by the materialnumber , DIN designation 100 Cr elementsRolling elements are classified, according to their shape, intoballs, cylindrical rollers, needle rollers, tapered rollers and barrel Rolling elements function is to transmit the force actingon the bearing from one ring to the other. For a high loadcarrying capacity it is important that as many Rolling elementsas possible, which are as large as possible, are accommodatedbetween the bearing rings. Their number and size depend onthe cross section of the is just as important for loadability that the Rolling elementswithin the bearing are of identical size. Therefore they are sorted according to grades.

8 The tolerance of one grade is generatrices of cylindrical rollers and tapered rollers havea logarithmic profile. This profile prevents, under normal loadconditions, life-reducing edge stresses at a tilting angle of upto 4 between inner ring and outer ring. BallCylindrical rollerNeedle rollerTapered rollerSymmetricalbarrel rollerAsymmetricalbarrel roller1234 FAG6 Rolling bearing componentsBearing rings CagesBearing ringsThe bearing rings inner ring and outer ring guide the Rolling elementsin the direction of rotation. Raceway grooves,lips and inclined running areas guide the Rolling elements andtransmit axial loads in transverse direction. Design NU and Ncylindrical roller bearings have lips only on one bearing ring;they can, therefore, accommodate shaft expansions as two rings of separablerolling bearings can be mountedseparately. This is of advantage if both bearing rings have to bemounted with a tight fit(see page 28).Separable bearings include, four-point bearings, double-row angular contact ball bearings with a split ring, cylindricalroller bearings, tapered roller bearings, thrust ball bearings, cylindrical roller thrust bearings and spherical roller bearings include, deep groove ball bear-ings, single-row angular contact ball bearings, self-aligningball bearings, barrel roller bearings and spherical roller a cage: to keep the Rolling elementsapart so that they do not rubagainst each other to keep the Rolling elements evenly spaced for uniform loaddistribution to prevent Rolling elements from falling out of separablebearingsand bearings which are swiveled out to guide the Rolling elements in the unloaded zone of transmission of forces is not one of the cage's are classified into pressed cages, machined cagesand moulded cagesare usually made of steel, but sometimes ofbrass, too.

9 They are lighter than machined metal cages. Since apressed cage barely closes the gap between inner ring and outer ring, lubricant can easily penetrate into the bearing . It isstored at the steel cages: prong-typecage (a) and rivet cage (b) fordeep groove ball bearings, window-type cage (c) for spher-ical roller bearingsMachined cagesof metal and textile laminated phenolic resinare made from tubes of steel, light metal or textile laminatedphenolic resin, or cast brass cages are mainly eligible for bearings of which small se-ries are produced. To obtain the required strength, large, heav-ily loaded bearings are fitted with machined cages. Machinedcages are also used where lip guidance of the cage is cages for high-speed bearings are in many casesmade of light materials such as light metal or textile laminatedphenolic resin to keep the forces of gravity = racewaysb = lipsabc7 FAGR olling bearing componentsCagesMachined brass cages: rivetedmachined cage (d) for deepgroove ball bearings, window-type cage (e) for angular contactball bearings, double prong typecage (f ) for spherical roller cagesofpolyamide 66 are produced by injectionmoulding and are used in many large-series moulding has made it possible to realize cage designswith an especially high load carrying capacity.

10 The elasticityand low weight of the cages are of advantage where shock-typebearing loads, great accelerations and decelerations as well astilting of the bearing rings relative to each other have to be accommodated. Polyamide cages feature very good sliding anddry running cages of glass fibrereinforced polyamide: window-type cage (g) for single-row angular contact ball bearings,window-type cage (h) for cylin-drical roller bearings, doubleprong type cage (i) for self-aligning ball bearingsCages of glass fibre reinforced polyamide PA66 are suitable forsteady-state operating temperatures of up to +120 C. In oil-lubricated bearings, additivescontained in the oil may reducethe cage life. At increased temperatures, aged oil may also havean impact on the cage life so that it is important to observe theoil change intervals. The limits of application for Rolling bear-ings with polyamide PA66-GF25 cages are indicated in theFAG catalogue WL 41 520EA, page 85. TI No. WL 95-4 contains a list of these distinctive feature of a cage is its type of guiding.