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Single Row Tapered Roller Bearings

The SKF standard range of single row tapered roller bearings (fig) covers the popular sizes of metric bearings manufactured to ISO 355:1977 and inch bearings which follow the ANSI/ABMA standard 19.2-1994. The range can be divided into
  • bearings for general use
  • high-performance bearings manufactured to the CL7C specifications
  • bearings with a flanged outer ring
  • as well as "Paired single row tapered roller bearings".For bearing arrangements operating in particularly difficult environments, for example, where the lubricating oil may be highly contaminated, where high operating temperatures prevail or where heavy deforming loads can be expected, SKF can supply particularly wear-resistant tapered roller bearings. Details are available on request.

    Standard designSKF tapered roller bearings for general use, including SKF bearings to Q specifications, have been optimized with regard to

    • sliding contact surfaces of the guide flange of the inner ring
    • roller end faces
    • raceway contact profile.

    In addition, highly accurate manufacturing processes make adjustment of the bearings against each other more reliable, which dramatically improves performance especially during the very first hours of operation.

    CL7C specification bearingsSKF tapered roller bearings produced to the CL7C specifications are intended for bearing arrangements supporting heavy axial loads, for example, gearbox pinion bearing arrangements. These bearings, which are mounted with preload, have special friction characteristics, higher running accuracy and higher axial load carrying capacity to provide a constant, accurate mesh.

    In contrast to the bearings for general use, CL7C specification bearings can be adjusted to within narrow limits using the frictional torque method, which considerably simplifies the adjustment process.

    With CL7C specification bearings there is practically no running-in wear. As a hydrodynamic lubricant film in the roller end/flange contacts is established from the outset, there is virtually no loss of preload and the preload can be maintained at a constant high level throughout operation.

    Bearings with flanged outer ringCertain sizes of SKF single row tapered roller bearings are also available with a flange on the outer ring (fig). Bearings having this external flange can be axially located in the housing to provide a simplified, more compact bearing arrangement. The housing bore is simpler to produce, as no shoulders are required.

    SKF Explorer bearings

    High performance SKF Explorer tapered roller bearings are shown with an asterisk in the product tables. SKF Explorer bearings retain the designation of the earlier standard bearings, e.g. 30310 J2/Q. However, each bearing and its box are marked with the name "EXPLORER".Upon request other standard tapered roller bearings can be manufactured in the SKF Explorer performance class. Moreover, the range of SKF Explorer tapered roller bearings is being continuously extended. Therefore SKF recommends checking the actual assortment by contacting the local SKF representative.

    SKF Energy Efficient (E2) bearings

    To meet the ever-increasing demand to reduce friction and energy consumption, SKF has developed the SKF Energy Efficient (E2) performance class for rolling bearings. Tapered roller bearings within this performance class are characterized by a frictional moment in the bearing that is at least 30% lower when compared to a same-sized standard SKF bearing.

    The bearings realized this substantial reduction of the frictional moment mainly by optimizing the internal geometry of the bearing, redesigning the cage and applying a new low-friction grease.

    Reduced operating temperatures improve lubrication conditions and enable extended lubrication intervals or higher speeds. The lower mass of the roller and cage assembly and reduced inertial forces in the bearing reduce the risk of skidding and smearing. Typical applications include wind energy transmissions, railway transmissions, ship transmissions and other heavy industrial transmissions.

    SKF E2 tapered roller bearings are available on request. For additional information, contact the SKF application engineering service.

    Bearing designations

    Metric bearings

    The series designations of metric tapered roller bearings with standardized dimensions according to ISO follow one of the following principles:

    • The series designations established in ISO 355:1977 comprising three symbols, a figure representing the contact angle and two letters for the diameter and width series followed by a three figure bore diameter identification (d in mm). The SKF designations are prefixed by the letter T, e.g. T2ED 045
    • Designations established prior to 1977 based on the system shown in the fig, e.g. 32206.

    Metric bearings with a J in the prefix follow the ABMA designation system, which is similar to the system used for inch bearings, see ANSI/ABMA Standard 19.2-1994.

    Inch bearingsInch tapered roller bearings are designated according to the ANSI/ABMA standard.

    Metric bearings that belong to the same series maintain the same relative cross section regardless of their size. This is not the case with inch bearings. All inch bearings within a series use the same cage and roller assembly but the inner and outer rings can have different sizes and designs.

    Any cone (the inner ring with cage and roller assembly) can be assembled with any cup (the outer ring) belonging to the same bearing series. For this reason the cone and cup have individual designations and can be supplied separately or as complete bearings (fig). The designations of the cones and cups as well as the series consist of a three to six-figure number which may be prefixed by one of the following letters or combination of letters: EL, LL, L, LM, M, HM, H, HH and EH. The prefixes characterize a bearing series from extra light to extra heavy. The basic principles of this system are described in ANSI/ABMA Standard 19.2-1994.

    The complete bearing designation consists of the cone designation followed by that of the cup, the two designations being separated by an oblique stroke (table 1).

    To shorten the complete bearing designations, abbreviations are used.

    Dimensions

    Metric bearingsThe boundary dimensions of metric single row tapered roller bearings listed in the product tables conform to ISO 355-1977 except for those bearings having a J in the designation prefix. These conform to the ANSI/ABMA Standard 19.1-1987.

    Inch bearingsThe boundary dimensions of inch bearings conform to AFBMA Standard 19-1974 (ANSI B3.19-1975). ANSI/ABMA Standard 19.2-1994 has subsequently replaced this standard, but this later standard no longer includes dimensions.

    TolerancesThe inner rings with roller and cage assembly and outer rings of SKF tapered roller bearings having the same designation are interchangeable. The tolerance for the total abutment width T of the bearing will not be exceeded if the cones and cups are interchanged.

    Metric bearingsSKF single row metric tapered roller bearings are manufactured to Normal tolerances as standard. Some bearings are also available with reduced width tolerance to tolerance class CLN specifications. Bearings having a J in the prefix are produced as standard to tolerance class CLN specifications.

    All bearings having an outside diameter above 420 mm have dimensional accuracy to tolerance class Normal specifications but the running accuracy is better than Normal, being to P6 specifications.

    The values for Normal and CLN tolerances correspond to ISO 492:2002 (classes Normal and 6X). The values for P6 running accuracy are in accordance with DIN 620-3:1964, which was withdrawn in 1988.

    Inch bearings

    SKF single row inch tapered roller bearings are produced to Normal tolerances as standard. On request, they may be supplied with higher accuracy to CL3 or CL0 tolerance class specifications and/or reduced width tolerances. Cones and cups having a width tolerance that differs from the Normal tolerance are identified by a designation suffix according to table 2 where the actual tolerance values are provided.

    The values for CL3, CL0 and Normal tolerances conform to ANSI/ABMA Standard 19.2-1994. The ISO standard 578:1987, which also covered these tolerance classes, was withdrawn in 1997.

    CL7C specification bearingsThe tolerances for CL7C specification bearings correspond to Normal tolerances except for the running accuracy which has been tightened considerably.

    Internal clearance and preloadThe internal clearance of single row tapered roller bearings can only be obtained after mounting and is determined by adjustment of the bearing against a second bearing, which provides location in the opposite direction. Further details can be found in the section "Bearing preload".

    Adjustment and running-inWhen adjusting tapered roller bearings against each other, the bearings must be rotated, so that the rollers assume their correct position, i.e. the large end face of the rollers must be in contact with the guide flange.

    Conventional tapered roller bearings normally have a relatively high friction torque during the first hours of operation, which drops to a lower level after the running-in period. During this running-in period, bearing temperature increases rapidly because of the high initial friction and falls off to an equilibrium level as the running-in phase is completed.

    This running-in phase is considerably reduced with bearings made to the SKF "Q" specification. In these bearings, the initial friction is also much lower, so that temperature increase is almost negligible. This also applies to the high-performance CL7C specification bearings, which are designed for easy adjustment.

    MisalignmentBearings with a Q designation suffix, SKF Explorer and SKF E2 bearings: 2 to 4 minutes of arc.

    If misalignment cannot be avoided, SKF recommends not to use standard design bearings without a Q designation suffix.

    The permissible angular misalignment between the inner and outer rings depends on the size and internal design of the bearing, the radial internal clearance in operation and the forces and moments acting on the bearing. As a result, only approximate values are provided here. Any misalignment will increase bearing noise and reduce bearing service life.

    CagesSKF single row tapered roller bearings are fitted with one of the following cages

    • a pressed window-type steel cage, roller centred, no designation suffix or suffix J1, J2 or J3 (fig)
    • an injection moulded window-type cage of glass fibre reinforced polyamide 66, roller centred, designation suffix TN9 (fig)
    • a steel pin-type cage (fig).

    NoteTapered roller bearings with a polyamide 66 cage can be operated at temperatures up to +120 C. The lubricants generally used for rolling bearings do not have a detrimental effect on polyamide cage properties, with the exception of a few synthetic oils and greases with a synthetic oil base, and lubricants containing a high proportion of EP additives when used at high temperatures.

    For bearing arrangements, which are to be operated at continuously high temperatures or under arduous conditions, SKF recommends using bearings with a pressed steel or high-temperature polymer cage.

    For detailed information about the temperature resistance and the applicability of cages, please refer to the section "Cage materials".

    Minimum loadTo achieve satisfactory operation, tapered roller bearings, like all ball and roller bearings, must always be subjected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions, the inertia forces of the rollers and cage, and the friction in the lubricant, can have a detrimental influence on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the rollers and raceways.

    The requisite minimum radial load to be applied to SKF standard tapered roller bearings can be estimated from

    Frm = 0,02 C

    and for SKF Explorer and SKF E2 bearings from

    Frm = 0,017 C

    where

    Frm = minimum radial load [kN]

    C = basic dynamic load rating [kN] (see product data)

    When starting up at low temperatures or when the lubricant is highly viscous, even greater minimum loads may be required. The weight of the components supported by the bearing, together with external forces, generally exceeds the requisite minimum load. If this is not the case, the single row tapered roller bearing must be subjected to an additional radial load, which can be achieved easily by applying preload. For additional information, refer to the section "Bearing preload".

    Equivalent dynamic bearing load

    P = Fr when Fa/Fr = e

    P = 0,4 Fr + YFa when Fa/Fr > e

    The values of the calculation factors e and Y can be found in the product tables.

    Equivalent static bearing load

    P0 = 0,5Fr + Y0Fa

    When P0 < Fr, P0 = Fr should be used. The value of the calculation factor Y0 can be found in the product table.

    Determination of axial forcesWhen a radial load is applied to a single row tapered roller bearing, the load is transmitted from one raceway to the other at an angle to the bearing axis and an internal axial force will be induced in the bearing. This must be considered when calculating the equivalent bearing loads for bearing arrangements consisting of two single bearings and/or bearing pairs arranged in tandem.

    The necessary equations are provided in table 3 for the various bearing arrangements and load cases. The equations are only valid if the bearings are adjusted against each other to practically zero clearance, but without any preload. In the arrangements shown, bearing A is subjected to a radial load FrA and bearing B to radial load FrB. Values of the loads FrA and FrB are always considered positive even when they act in the direction opposite to that shown in the figures. The radial loads act at the pressure centres of the bearings (dimension a in the product table).

    In addition an external force Ka acts on the shaft (or on the housing). Cases 1c and 2c are also valid when Ka = 0. Values of the factor Y can be found in the product table.

    Supplementary designations

    Prefixes The designation prefixes used to identify certain features of SKF single row tapered roller bearings are explained in the following.

    DesignationFeatures
    E2.SKF Energy Efficient bearing
    JMetric bearing following the ABMA designation system (ANSI/ABMA Standard 19.2-1994)

    SuffixesThe designation suffixes used to identify certain features of SKF single row tapered roller bearings are explained in the following.

    DesignationBearing Features
    BSteeper contact angle than standard design
    CLNReduced tolerances for ring widths and total (abutment) width; corresponds to ISO tolerance class 6X
    CL0Accuracy to ABMA tolerance class 0 for inch bearings
    CL3Accuracy to ABMA tolerance class 3 for inch bearings
    CL7AHigh-performance design for pinion bearing arrangements (superseded by CL7C)
    CL7CHigh-performance design for pinion bearing arrangements
    HA1Case-hardened inner and outer rings
    HA3Case-hardened inner ring
    HN1Inner and outer ring with special surface heat treatment
    HN3Inner ring with special surface heat treatment
    J ressed window-type steel cage, roller centred. A figure following the J indicates a different cage design
    P6Dimensional and running accuracy to old ISO tolerance class 6, better than Normal
    QOptimized contact geometry and surface finish
    RFlanged outer ring
    TN9Injection moulded window-type cage of glass fibre reinforced polyamide 66, roller centred
    U.U combined with a one-figure number identifies reduced total width tolerance.

    Examples:

    DesignationBearing Features
    U2Total width tolerance +0,05/0 mm
    U4Total width tolerance +0,10/0 mm

    see also table 2

    DesignationBearing Features
    VA321Optimized internal design
    VA606Crowned raceway on bearing rings and special heat treatment
    VA607Crowned raceway on bearing rings and special heat treatment
    VB022Chamfer dimension at large outer ring face 0,3 mm
    VB026Chamfer dimension at large inner ring side face 3 mm
    VB061Chamfer dimension at large inner ring side face 8 mm
    VB134Chamfer dimension at large inner ring side face 1 mm
    VB406Chamfer dimension at large inner ring side face 3 mm and at large outer ring side face 2 mm
    VB481Chamfer dimension at large inner ring side face 8,5 mm
    VC027Modified internal geometry for increased permissible misalignment
    VC068Increased running accuracy and special heat treatment
    VE174One locating slot in outer ring at large outer ring side face, increased running accuracy
    VQ051Modified internal geometry for increased permissible misalignment
    VQ267Reduced inner ring width tolerance, 0,025 mm
    VQ495As CL7C but with reduced or displaced tolerance for the outside diameter
    VQ506Reduced inner ring width tolerance
    VQ507As CL7C but with reduced or displaced tolerance for the outside diameter
    VQ523As CL7C but with reduced inner ring width tolerance and reduced or displaced tolerance for the outside diameter
    VQ601Accuracy to ABMA tolerance class 0 for inch bearings
    WModified ring width tolerance, +0,05/0 mm
    XBoundary dimensions changed to conform to ISO

    Design of bearing arrangements

    When designing bearing arrangements incorporating single row tapered roller bearings it is necessary to consider the special characteristics of these bearings. Because of their internal design, they cannot be used singly and a second bearing is required (fig); alternatively a paired set (fig) may be used. When the arrangement comprises two single row bearings they must be adjusted against each other until the desired operational clearance or preload is obtained; see under "Bearing preload".

    A correctly dimensioned operational clearance or preload is vital to the correct performance of single row tapered roller bearings and also to the operational reliability of the arrangement. If the operational clearance is too large, the full load carrying capacity of the bearing will not be exploited. If the preload is too great then frictional losses will increase, as will operating temperature. In both cases the bearing service life could be substantially reduced.

    Fits for inch-size bearings

    Suitable fits for inch-size tapered roller bearings can be obtained based on the recommended fits for metric bearings. However, since inch-size bearings, in contrast to metric bearings, are machined to plus tolerances, the deviations for shaft and housing cannot be applied directly and must be modified to take account of the plus tolerances. Reference should therefore be made to the tables below, which provide the same degree of interference or clearance as the recommended metric tolerances.

    Table 2a:Modified shaft diameter deviations g6, h6, j5, j6, js6, k5
    Table 2b:Modified shaft diameter deviations k6, m5, m6, n6, p6
    Table 3a:Modified housing bore diameter deviations H7, J7, J6, K6, K7
    Table 3b:Modified housing bore diameter deviations M6, M7, N7, P7


    Tapered roller bearings | Single row tapered roller bearings | Paired single row tapered roller bearings | Double row tapered roller bearings | Four-row tapered roller bearings

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    This page is still under construction. All bearing information remains the property and copyright of SKF Group.