SKF 925 Catalogue - Bearing Stock Shop

Table of contentsBall & Roller Unit BlocksSleevesBall Bearing typesIntroduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213Metric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288Pillow blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216Inch4 Bolt flanged units. . . . . . . . . . . . . . . . . . . . . . . . 223Inch USA version . . . . . . . . . . . . . . . . . . . . . . . . . 3022 Bolt flanged units. . . . . . . . . . . . . . . . . . . . . . . . 226Withdrawal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294Take-up units . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230Air handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232Maintenance and LubricationProductsConCentra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238Mechanical tools. . . . . . . . . . . . . . . . . . . . . . . . . . 315Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239Bearing heaters . . . . . . . . . . . . . . . . . . . . . . . . . . 318Pressed steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231Hydraulic tools . . . . . . . . . . . . . . . . . . . . . . . . . . . 320Roller Bearing typesInstruments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249Lubricants and lubricators . . . . . . . . . . . . . . . . . . 324Pillow blocks standard & ConCentra . . . . . . . . . . 250Bearing greases and charts . . . . . . . . . . . . . . . . . 327Flanged units standard & ConCentra. . . . . . . . . . 252Take-up units . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259Other ProductsConCentra metric . . . . . . . . . . . . . . . . . . . . . . . . . 261Needle roller bearings . . . . . . . . . . . . . . . . . . . . . 331Collar mounted roller bearings & accessories . . . 262Track runner bearings . . . . . . . . . . . . . . . . . . . . . 333Supportive rollers . . . . . . . . . . . . . . . . . . . . . . . . . 333Marathon Series, CompositeCam followers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 333Pillow blocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263Split spherical and split CARB 2 Bolt flanged units. . . . . . . . . . . . . . . . . . . . . . . . 265Toroidal roller bearings . . . . . . . . . . . . . . . . . . 3344 Bolt flanged units. . . . . . . . . . . . . . . . . . . . . . . . 267Slewing bearings . . . . . . . . . . . . . . . . . . . . . . . . . 335Tapped base. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269High-precision bearings for machine tools. . . . . . 3373 Bolt bracketed flanged . . . . . . . . . . . . . . . . . . . 271Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339Narrow slot take-Up units. . . . . . . . . . . . . . . . . . . 273SKF Systems Solutions / SKF Copperhead . . . . . 339Wide slot take-up units. . . . . . . . . . . . . . . . . . . . . 275Spindle units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340Stainless take-up frames . . . . . . . . . . . . . . . . . . . 277Linear motion products. . . . . . . . . . . . . . . . . . . . . 342Coated cast iron pillow blocks . . . . . . . . . . . . . . . 279Plain bearings. . . . . . . . . . . . . . . . . . . . . . . . . . . . 344Coated cast iron 2 bolt flanged units . . . . . . . . . . 280Coated cast iron 4 bolt flanged units . . . . . . . . . . 281Part number index . . . . . . . . . . . . . . . . . . . . . . . 347Coated cast iron tapped base units . . . . . . . . . . . 282Cast stainless pillow block units. . . . . . . . . . . . . . 283Cast stainless 2 bolt flanged units . . . . . . . . . . . . 284Cast stainless 4 bolt flanged units . . . . . . . . . . . . 285Cast stainless tapped base units . . . . . . . . . . . . . 2863

Bearing characteristicsThis matrix can only provide a rough guide so that in each individual case it is necessary to make a more qualified selection referring tothe information given on the following pages or www.skf.ca (Interactive Engineering Catalogue).Bearing TypeSeriesDeep Groove Ball Bearings16000, 200, 300, 6000, 61800, 61900,6200, 6300, 6400Angular Contact Ball Bearings7200, 7300, 74003300, 5200, 5300, BA2B 459000Four-point Contact Ball BearingsQJ200, QJ300Self-aligning Ball Bearings1200, 1300, 1400, 2200, 2300Thrust Ball Bearings51000, 5200053000, 54000Spherical Roller Thrust Bearings29200, 29300, 29400Cylindrical Roller BearingsN, NJ, NU (200, 300, 400)NUP (200, 300, 400)NNU4000, NN3000Full Complement CylindricalRoller BearingsNCF, NJGNNC4800, NNCF, NNCL, NNFSpherical Roller Bearings21000, 22000, 23000, 24000,452000, 453000, I seriesCARB C2200, C2300, C3000, C3100, C3200,C39/100, C4000, C5900, C6000Needle Roller BearingsHK, NA, NK, NKI, NKIS, NKS, RNATaper Roller Bearings30000, 31000, 32000, 33000, T2, T4, T731300DF, 32000DF4

Bearing characteristicsCharacteristics – suitability of bearing ementpossiblein bearingtypical applicationTextiles Power tools, Electric motors,Pumps, GearboxesPumps, Compressors, CentrifugesPumps, Compressors, CentrifugesCompressorsFans, Paper making machinesPlastic extruder tools, Crane hooksPlastic extruder tools, Crane hooksTunnel boring machines,Wind turbines, Cranes, Pumps,Electric motorsTraction motors, Electric motors,GearboxesTraction motors, Electric motors,GearboxesPrecision machines, SpindlesElevators, GearboxesCranes, Steel rolling mills, Wire ropes,SheavesFans, Paper, Gearboxes, Crushers,Vibrating screensPaper making machines,Gearboxes, Fans, Electric motorsGearboxes (planetary), AlternatorsGearboxes, Cone crushersGearboxes, Rail car axleKeyexcellentgoodfairpoorunsuitable5

Bearing lifeLoad CarryingCapacity andLifeThe size of a bearing to be used for anapplication is initially selected on the basisof its load carrying capacity in relation tothe loads to be carried and the requirements regarding life and reliability.Numerical values termed basic load ratingsare used in the calculations to express loadcarrying capacity. Values for the basicdynamic load rating C and the basic staticload rating C0 are quoted in the bearingtables.The basic static load rating is defined inaccordance with ISO 76-1990 as the staticload which corresponds to a calculatedcontact stress at the center of the mostheavily loaded rolling element/racewaycontact of: 667,000 psi (4,600 Mpa) for self-aligningball bearings; 609,000 psi (4,200 Mpa) for all other ballbearings;Basic load ratingsThe basic dynamic load rating C is used forcalculations involving dynamically stressedbearings, for example, when selecting abearing which is to rotate under load. Itexpresses the bearing load which will givean ISO basic rating life (defined below) of1,000,000 revolutions.The basic dynamic load ratings of SKFbearings have been determined inaccordance with the methods prescribed byISO 281:1990/Amd.1:2000 and ABMA Stds.9 and 11. The values are based on thematerial and manufacturing techniquesused for SKF standard production. Theyapply to loads which are constant both inmagnitude and direction, for radial bearingsradial loads, and for thrust bearings axialloads which act centrically.The basic static load rating C0 is used incalculations when the bearings are to rotateat very slow speeds, are to be subjected tovery slow oscillating movements, or are tobe stationary under load during certainperiods. It must also be taken into accountwhen heavy shock loads of short durationact on a rotating (dynamically stressed)bearing.6 580,000 psi (4,000 Mpa) for all rollerbearings.This stress produces a total permanentdeformation of rolling element and racewaywhich is approximately 0.0001 of the rollingelement diameter. The loads are purelyradial for radial bearings and centricallyacting axial loads for thrust bearings.LifeThe life of a rolling bearing is defined asthe number of revolutions (or the number ofoperating hours at a given constant speed)which the bearing is capable of enduringbefore the first sign of fatigue (flaking,spalling) occurs on one of its rings or rollingelements.It is, however, evident from both laboratorytests and practical experience thatseemingly identical bearings operatingunder identical conditions have differentlives. A clearer definition of the term “life” istherefore essential for the calculation ofbearing size. All information presented bySKF on dynamic load ratings is based onthe life that 90% of a sufficiently largegroup of apparently identical bearings canbe expected to attain or exceed. This iscalled the basic rating life and agrees withthe ISO definition. The median life isapproximately five times the calculatedbasic rating life.There are several other bearing “lives”.One of these is the “service life”, which isthe actual life achieved by a specificbearing before it fails. Failure is notgenerally by fatigue in the first instance butby wear, corrosion, seal failure, etc.Another is “specification life”. This is the lifespecified by an authority and based onhypothetical load and speed data suppliedby the same authority. It is generally arequisite L10 (basic rating life), and it isassumed that the authority has related thespecification to experience gained withsimilar machinery, so that adequate servicelife will be obtained.Practical experience and modern researchhave shown that, under special conditions,SKF bearings attain a much longer life thanpredicted by the standardized life calculation methods mentioned above, particularlywhen loads are light. These specialconditions apply when the rolling surfaces(raceways and rolling elements) are effectivelyseparated by a lubricant film and whensurface damage caused by contaminants islimited. In fact, under ideal conditions, it ispossible to speak of infinite life.

Bearing lifeSelectingBearing SizeUsing the LifeEquationsBearing life can be calculated with variousdegrees of sophistication, depending on theaccuracy with which the operatingconditions can be defined.Basic rating life equationThe simplest method of life calculation is touse the ISO or ABMA equation for basicnon-adjusted rating life which is:()L10 CPpwhereL10 basic rating life, millions ofrevolutionsC basic dynamic load ratingP equivalent dynamic bearing loadp exponent of the life equationFor bearings operating at constant speed itmay be more convenient to deal with abasic rating life expressed in operatinghours using the equation:L10h 1 000 000 L1060 nwhereL10h basic rating, operating hoursn rotational speed, r/minSKF rating lifeFor modern high quality bearings the basicrating life can deviate significantly from theactual service life in a given application.Service life in a particular applicationdepends on a variety of influencing factorsincluding lubrication, the degree ofcontamination, misalignment, properinstallation and environmental conditions.Therefore ISO 281:1990/Amd 2:2000contains a modified life equation tosupplement the basic rating life. This lifecalculation makes use of a modificationfactor to account for the lubrication andcontamination condition of the bearing andthe fatigue limit of the material.ISO 281:1990/Amd 2:2000 also makesprovisions for bearing manufacturers torecommend a suitable method forcalculating the life modification factor to beapplied to a bearing based on operatingconditions. The SKF life modification factoraSKF applies the concept of a fatigue loadlimit Pu analogous to that used whencalculating other machine components. Thevalues of the fatigue load limit are given inthe product tables. Furthermore, the SKF lifemodification factor aSKF makes use of thelubrication conditions (viscosity ratio k) and afactor nc for contamination level to reflect theapplication’s operating conditions.The equation for SKF rating life is inaccordance with 281:1990/Amd 2:2000()Lnm a1 aSKF L10 a1 aSKF CPpIf the speed is constant, the life can be expressed in operating hours, using the equation6Lnmh 1 0 Lnm60nwhereLnm SKF rating life (at 100 -n %reliability), millions of revolutionsLnmh SKF rating life (at 100 - n %reliability), operating hoursa1 life adjustment factor for reliabilityaSKF SKF life modification factorC basic dynamic load rating, kNP equivalent dynamic bearing load, kNn rotational speed, r/minp exponent of the life equation 3 for ball bearings 10/3 for roller bearingsThis type of evaluation can be performedby SKF Application Engineers. Additionalinformation on this subject can be found inthe SKF General Catalogue (5000) or theInteractive Engineering Catalogue availableat www.skf.ca.7

Bearing lifeStatic LoadCarryingCapacityBearing size should be selected on thebasis of the basic static load rating C0instead of on bearing life when one of thefollowing conditions pertains: the bearing is stationary and is subjected tocontinuous or intermittent (shock) loads; the bearing makes slow oscillating oralignment movements under load; the bearing rotates under load at veryslow speed and is only required to havea short life (the life equation in this case,for a given equivalent load P would givesuch a low requisite basic dynamic loadrating C, that the bearing selected onthis basis would be subjected toconsiderable over-loading in service); the bearing rotates and, in addition to thenormal operating loads, has to sustainheavy shock loads which act during afraction of a revolution.In all these cases, the permissible load for abearing is determined not by material fatiguebut by the permanent deformation caused bythe load at the rolling element/ racewaycontact. Loads acting on a stationary bearingor one which is slowly oscillating, as well asshock loads on a rotating bearing which actfor only part of a revolution, produce flattenedareas on the rolling elements andindentations in the raceways.The indentations may be irregularly spacedaround the raceway, or they may be evenlyspaced at positions corresponding to thespacing of the rolling elements. If the loadacts for several revolutions of the bearing,the deformation will be evenly distributedover the whole raceway. The permanentdeformations in the bearing can lead tovibration in the bearing, noisy operationand increased friction; it is also possiblethat the internal clearance will increase orthe character of the fits may be changed.The extent to which these changes aredetrimental to bearing performancedepends on the demands placed on thebearing in a particular application. It istherefore necessary to ensure thatpermanent deformations cannot occur, oroccur to a very limited extent only, byselecting a bearing with a sufficiently highstatic load carrying capacity, if one of thefollowing demands has to be satisfied: silent running (for example, electricmotors) vibration-free running (for example,machine tools) constant bearing friction torque(for example, measuring equipment andtest apparatus) low starting friction under load(for example, cranes)When determining bearing size based onstatic load carrying capacity, a given safetyfactor s0 which represents the relationshipbetween the basic static load rating C0 andthe equivalent static bearing load P0 isused to calculate the requisite basic staticload rating.Table 6 Guideline values for static safety factor s0Type ofoperationRotating bearingsRequirements regarding quiet runningunimportant llRollerBallRollerbearings bearings bearings bearings bearingsBallRollerbearings l0.5111.523.50.51 2.5 1.5 3 2 4 1 2Pronouncedshock loads1) 1.5For spherical roller thrust bearings it is advisable to use s0 41) Where the magnitude of the load is not known values of s which are at least as large as those0quoted above should be used. If the magnitude of the shock loads is exactly known, smaller valuesof s0 can be applied8Requisite basic static load ratingThe requisite basic static load rating C0can be determined fromC0 s0 P0whereC0 basic static load ratingP0 equivalent static bearing loads0 static safety factorGuideline values based on experience aregiven in table 6 for the static safety factors0 for ball and roller bearings for varioustypes of operation and requirementsregarding smooth running.At elevated temperatures the static loadcarrying capacity of bearings is reduced;further information will be supplied onrequest.Checking the static load carryingcapacityFor dynamically loaded bearings whichhave been selected with reference to life itis advisable, where the equivalent staticbearing load is known, to check that thestatic load carrying capacity is adequateusingS0 C0P0If the s0 value obtained is less than therecommended guideline value (see table 6)then a bearing having a higher basic staticload rating should be selected.

Bearing internal clearance, Vibration FrequenciesBearingInternalClearanceBearing internal clearance is defined as thetotal distance through which one bearingring can be moved relative to the other inthe radial direction (radial internalclearance) or in the axial direction (axialinternal clearance). See figure 1.Figure 1It is necessary to distinguish betweenthe internal clearance of a bearing beforemounting and the internal clearance in amounted bearing which has reached itsoperating temperature (operational clearance).The initial internal clearance (before mounting)is normally greater than the operationalclearance because different degrees ofinterference in the fits and differences inthermal expansion of the bearing rings and theassociated com-ponents cause the rings to beexpanded or compressed.The radial internal clearance of a bearing isof considerable importance if satisfactoryoperation is to be obtained. As a generalrule, ball bearings should have anoperational clearance which is virtuallyzero, or there may be a slight preload.Cylindrical and spherical roller bearings, onthe other hand, should always have someresidual clearance – however small – inoperation. The same is true of taper rollerbearings except in bearing arrangementswhere stiffness is desired, e.g. pinionbearing arrangements, where the bearingsare mounted with a certain degree ofpreload.Tables giving the clearance values forthe various bearing types will be found inthe text preceding the relevant bearingtable section. For paired single rowangular contact ball bearings and taperroller bearings, double row angularcontact ball bearings and four-pointcontact ball bearings, values for the axialinternal clearance are given instead ofradial clearance, as the axial clearanceis of greater importance in applicationdesign for these bearing types.The bearing internal clearance referred toas Normal (CN or C0) has been selected sothat a suitable operational clearance will beobtained when bearings are mounted withthe fits usually recommended and operatingconditions are normal. Where operating andmounting conditions differ from the normal,for example, where interference fits areused for both bearing rings, unusualtemperatures prevail etc. bearings withgreater (C3) or smaller (C2) internalclearance than Normal are required. In suchcases, it is recommended that the residualclearance in the bearing after it has beenmounted should be checked.Bearings having an internal clearance otherthan Normal are identified by thesuffixes C1 to C5.VibrationFrequenciesFrequencies for most SKF bearings can befound at www.skf.ca under InteractiveEngineering Catalogue.9

SKF ExplorerSKF ExplorerA new level of performanceOver the years, manufacturing andmaterials research and processimprovements have enabl

bearing accessories, bearing housings, industrial seals and linear motion products. These are available in dedicated catalogues. The SKF Group is the world's largest manufacturer of anti-friction bearings and accessories with some 100 manufacturing sites worldwide and sales companies