ansi_afbma std 11-1990

ANSVAFBMA Std 1 I- 1090 (Revision of

ANSIIAFBMA Std 1 l-1978)

M ATIONAL ST

s

LOAD RATINGS AND FATIGUE LIFE FOR ROLLER BEARINGS

Copyright0 American Bearing Manufacturers Association, Inc. This reproduction made under license agreement by CSSinfo, (734) 930-9277. No part of the printed publication, nor any part of the electronic tile may be reproduced or transmitted in any form, including transmittal by e-mail, by file transfer protocol (FTP), or by being made part of a network-accessible system, without the prior written permission of the copyright owner.

Sponsor

The Anti-Friction Bearing Manufacturers Association, Inc.

Approved July 17, IYAi

American National Standards institute, Inc.

American National Standard

Approval of an American National Standard requires verification by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer.

Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerned effort be made toward their resolution.

The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standards.

The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for inter- pretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard.

CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of approval. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Stan- dards Institute.

Published by

The Anti-Friction Bearing Manufacturers Association, Inc. 1101 Connecticut Ave. N.W., Suite 7@0

Washington, D.C. 20036

Copyright 1990 by The Anti-Friction Bearing Manufacturers Association, Inc.

FOREWORD

(This Foreword is not a part of American National Standard, Load Ratings and Fatigue Life for Roller Bearings.)

This revision of ANWAFBMA Standard 11 has as its principal feature: The utilization of the factor f,, which depends on the geometry of the bearing components, the accuracy to which the various components are made and contemporary, normally used material and its manufacturing quality.

This standard is in close conformity with IS0 76-1987 (Rolling bearings- Static load ratings) and with IS0 DIS 281-1989 (Rolling bearings-Dynamic load ratings and rating life). Any significant differences, where they occur, are indicated in this standard.

The principal difference between this standard and IS0 DIS 281 is the use of the f,, factor which combined the f, and b, factors used in IS0 281. Dynamic load ratings calculated for the same bearing should have the same value, however, when following either this or the IS0 Standard unless noted otherwise in this standard.

The life adjustment factor for special bearing properties, a2, intended for use with capacities calculated in accordance with previous revisions of this Standard may not be valid for use with the current capacities. The present fc, values incorporate material and processing improvements which were previously adjusted by means of the a2 factor.

Copies of IS0 Standards concerning Rolling Contact Bearings (Ball and Roller Bearings) are available from the American National Standards Insti- tute.

Suggestions for the improvement of this standard gained from its use will be welcomed. Such suggestions should be sent to the American National Standards Institute, Inc., 1430 Broadway, New York, N.Y., 10018.

The officers of Accredited Standards Committee 83 operating under Amer- ican National Standards Institute Procedures and the organizations repre- sented at the time this standard was submitted are as follows:

S. R. Ahlman, Chairman G. T. Satterfield, Secretary

Anti-Friction Bearing Manufacturers Association Hydraulic Institute National Machine Tool Builders Association Society of Tribologists and Lubrication Engineers U.S. Department of the Navy U.S. Department of Defense, DISC

1 4 7

-Terminology -Tolerance Definitions and Gaging Practices -Shaft and Housing Fits for Metric Radial Ball and Roller Bearings

(Except Tapered Roller Bearings) Conforming to Basic Boundary Plans

8.1 8.2 9 10 11 12.1 12.2 13 14 15

-Ball and Roller Bearing Mounting Accessories, Metric Design -Ball and Roller Bearing Mounting Accessories, Inch Design -Load Ratings and Fatigue Life for Ball Bearings -Metal Balls -Load Ratings and Fatigue Life for Roller Bearings -Instrument Ball Bearings, Metric Design -Instrument Ball Bearings, Inch Design -Rolling Bearing Vibration and Noise -Housing for Bearings With Spherical Outside Surfaces -Ball Bearings With Spherical Outside Surfaces and Extended

16.1 16.2 17 18.1 18.2 19 20

Inner Ring Width (Includes Eccentric Locking Collars) -Airframe Ball, Roller and Needle Roller Bearings, Metric Design -Airframe Ball, Roller and Needle Roller Bearings, Inch Design -Needle Rollers, Metric Design -Needle Roller Bearings-Radial, Metric Design -Needle Roller Bearings-Radial, Inch Design -Tapered Roller Bearings, Radial, Metric Design -Radial Bearings of Ball, Cylindrical Roller and Spherical Roller

Types, Metric Design 21.1 -Thrust Needle Roller and Cage Assemblies and Thrust Washers,

Metric Design 21.2 -Thrust Needle Roller and Cage Assemblies and Thrust Washers,

Inch Design 22.2 -Spherical Plain Bearings, Joint Type, Inch Design 23.2 -Thrust Bearings of Tapered Roller Type, Inch Design 24.1 -Thrust Bearinas of Ball, Cvlindrical Roller and Spherical Roller

24.2 Types, Metricbesign

,

-Thrust Bearings of Ball and Cylindrical Roller Types, Inch Design

AFBMA Standards for

Ball and Roller Bearings and Balls

An AFBMA Standard is intended as a guide to aid the manufacturer, the consumer and the general public. The existence of an AFBMA Standard does not in any respect preclude anyone, whether he has approved the Standard or not from manufacturing, marketing, purchasing, or using products, processes, or procedures not conforming to the standard. AFBMA Standards are subject to revision or withdrawal at any time and users who refer to an AFBMA Standard should satisfy themselves that they have the latest information from the Association.

Load Ratings and Fatigue Life For Ball Bearings

SECTION CONTENTS

PAGE

1. Introduction . . 1.1 Purpose of Standard 1.2 Life Criterion . . 1.3 Static Load Criterion .

2. Symbols . . . .

3. Definitions . . .

$2 3:3

Z’Z 3:6

;.; 3:9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21

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. . .

. .

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. .

.

.

. . . .

. . .

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.

. .

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Life ...................................... Reliability .................................. Static Load ................................. Pitch Diameter of a Roller Set, D,, ..................... Basic Rating Life, L,, ............................ Adjusted Rating Life, L,, .......................... Basic Dynamic Radial Load Rating, C, ................... Basic Static Radial Load Rating, C,, .................... Basic Dynamic Axial Load Rating, C, ................... Basic Static Axial Load Rating, C,, ..................... Dynamic Equivalent Radial Load, P, .................... Static Equivalent Radial Load, P,, ...................... Dynamic Equivalent Axial Load, P, ..................... Static Equivalent Axial Load, P,, ...................... Roller Diameter, D,, ............................. Roller Length, L,, .............................. Nominal Contact Angle, cx .......................... Line Contact ................................. Point Contact ................................ Optimized Contact ............................. Conventional Operating Conditions .....................

4. Scope ...................... 4.1 Bearing Types .................

4.1 .I General 4.1.2 Basic Types : : :

.............

............. 4.1.3 Double Row ................

4.2 Limitations .................... 4.2.1 Truncated’ Contact Area .......... 4.2.2 Materials .................. 4.2.3 Bearing Types ............... 4.2.4 Lubrication ................. 4.2.5 Ring Support and Alignment ....... 4.2.6 Internal Clearance ............. 4.2.7 High Speed Effects ............ 4.2.8 Stress Concentrations ........... 4.2.9 Tolerances ................. 4.2.10 Plastic Deformation in the Contact Area

4.3 Operating Parameters .............

1 1 1 1

2

3

i

: 3 3

i 3 3 4 4 4 4 4 4 4 4 4

t

4 4

:: 5 5 5 5 5 5 5 5 5 5 5

:

5. Radial Roller Bearings . . . . 5.1 Basic Dynamic Radial Load Rating

5.1 .I Bearing Combinations 5.2 Dynamic Equivalent Radial Load . .

5.2.1 Bearing Combinations . . . . . . . . 5.3 Basic Rating Life . . . . . . . 5.4 Basic Static Radial Load Rating

5.4.1 Bearing Combinations . . . . . 5.5 Static Equivalent Radial Load . . . .

5.5.1 Bearing Combinations . . . , . . .

. .

.

6. Thrust Roller Bearings . . . . . . . . . . . 6.1 Basic Dynamic Axial Load Rating . . . . .

6.1 .I Single Row Bearings . . . . . . . 6.1.2 Bearings with Two or More Rows of Rollers 6.1.3 Bearing Dynamic Equivalent Axial Load

::: Dynamic Equivalent Axial Load Basic Rating Life .

6.4 Basic Static Axial Load Rating . . . . 6.5 Static Equivalent Axial Load . . . . , . . . .

.

. .

. .

. .

. .

7. Adjusted Rating Life . . . . . . . . . . . . . . . . . . . . . 7.1 General

Limitations 1 1 . . . . . . . . . . . . . . . . . . . .

7.2 7.3 Life Adjustment’Fadtdr for keliability’a~ : : : : : : : : : : : 7.4 Life Adjustment Factor for Special Bearing Properties, a2 . 7.5 Life Adjustment Factor for Operating Conditions, a3

.

.

.

.

.

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6 6 6 6 9 9 9 9 9

IO

10 10

:: 11 11 12 14 14

14 14

;: 15 15

Table No.

RADIAL ROLLER BEARINGS

LIST OF TABLES

Title Page

1. 2. 3.

4.

5. 6. 7. 8.

Values of f,, ................. Values of X and Y .............. Values of X, and Y, .............

THRUST ROLLER BEARINGS

Values of f,, for cylindrical roller bearings, tapered roller bearings and needle roller bearings with machine rings Values of f,, for drawn cup needle roller bearings :

......

....... Values of f,, for spherical roller bearings ............. ValuesofXandY .......................... Life Adjustment Factors for Reliability ...............

7 9

10

11 12 13 13 15

Load Ratings and Fatigue Life for Roller Bearings

1. INTRODUCTION

1 .l Purpose of Standard

Roller bearing performance is a function of many variables. These include the bearing design, the characteristics of the material from which the bearings are made, the way in which they are manufactured, as well as many variables associated with their application. The only sure way to establish the satisfactory operation of a bearing selected for a specific application is by actual performance in the application. As this is often impractical, another basis is required to estimate the suitability of a particular bearing for a given application. This is the purpose of this standard.

This standard specifies the method of calculating the basic dynamic load rating of rolling bearings within the size ranges shown in the relevant ANSVAFBMA standards, manufactured from contemporary, commonly used, good quality hardened steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of rolling contact surfaces.

This standard also specifies the method of calculating the basic rating life, which is the life associated with 90% reliability, with commonly used material and manufacturing quality, and with conventional operating conditions. In addition, it specifies the method of calculating adjusted rating life, in which various reliabilities, special bearing properties and specific operating conditions are taken into account by means of life adjustment factors.

Furthermore, this standard specifies the method of calculating the basic static load rating and the static equivalent load for roller bearings within the size ranges shown in the relevant ANSVAFBMA Standards, manufactured from good quality hardened steel, in accordance with good manufac-

turing practice and basically of conventional design as regards the shape of rolling contact surfaces.

1.2 Life Criterion

Even if roller bearings are properly mounted, adequately lubricated, protected from foreign matter, and are not subjected to extreme operating conditions, they can ultimately fatigue. Under ideal conditions, the repeated stresses developed in the contact areas between the roller and the raceways eventually can result in fatigue of the material which manifests itself as spall- ing of the load carrying surfaces. In most applications the fatigue life is the maximum useful life of a bearing. This fatigue is the criterion of life used as the basis for the first part of this standard.

Fatigue life calculated in accordance with this standard does not represent the maximum that can be attained by applying all known technology to roller bearing design and application. Neither does it represent the minimum that should be expected of a bearing made by a producer lacking skill and experience in the design and manufacture of roller bearings, even though the bearing meets the geometric parameters given below. The calculated fatigue life represents the performance normally expected from high quality bearings made by reputable manufacturers. Manu- facturers can supply longer lived bearings by the application of advanced materials and manufacturing processes. The present standard has evolved as a means for bearing users to specify a reasonable standard of performance for the bearing they wish to purchase.

1.3 Static Load Criterion

A static load is a load acting on a non- rotating bearing. Permanent deformations appear in rollers and raceways under a

1

static load of moderate magnitude and in- crease gradually with increasing load.

It is often impractical to establish whether the deformations appearing in a bearing in a specific application are permissible by testing the bearing in that application. Other methods are therefore required to establish the suitability of the bearing selected.

Experience shows that a total permanent deformation of 0.0001 of the rolling element diameter, at the center of the most heavily loaded roller/raceway contact, can be tol- erated in most bearing applications without the subsequent bearing operation being impaired. The basic static load rating is, therefore, given a magnitude such that approximately this deformation occurs when the static equivalent load is equal to the load rating.

Tests indicate that a load of the magnitude in question may be considered to cor- respond to a calculated contact stress of

- 4000 MPa (580,000 psi) for all roller bearings

at the center of the most heavily loaded rolling element/raceway contact. The formulae and factors for the calculation of the basic static load ratings are based on these contact stresses.

The permissible static equivalent load may be smaller than, equal to or greater than the basic static load rating, depending on the requirements for smoothness of operation and friction, as well as on actual contact surface geometry. Bearing users without previous experience of these conditions should consult the bearing manufacturers.

2. SYMBOLS

C, = basic dynamic radial newtons (pounds)

load rating,

C,, = basic static radial load rating, newtons (pounds)

C, = basic dynamic axial load rating, newtons (pounds)

C,, = basic static axial load rating, newtons (pounds)

D,,=pitch diameter of roller set, millimetres (inches)

D,, = roller diameter applicable in the calculation of load ratings, millimetres (inches)

F, = bearing radial load = radial component of the actual bearing load, newtons (pounds)

F, = bearing axial load = axial component of the actual bearing load, newtons (pounds)

L,, = basic rating life, in million revolutions

L,, =adjusted rating life, in million revolutions

L,, =roller length applicable in the calculation of load ratings, millimetres (inches)

P, =dynamic equivalent radial load, newtons (pounds)

P,, = static equivalent radial load, newtons (pounds)

P, =dynamic equivalent axial load, newtons (pounds)

P,, =static equivalent axial load, newtons (pounds)

X =dynamic radial load factor

X, =static radial load factor

Y =dynamic axial load factor

Y, =static axial load factor

Z = number of rolling elements in a single row bearing; number of rolling elements per row of a multi-row bearing with the same number of rolling elements per row

al = life adjustment factor for reliability

a2 = life adjustment factor for special bearing properties

a3 = life adjustment factor for operating conditions

e = limit value of F$F, for the applicability of different values of factors X and Y

=a factor which depends on the geometry of the bearing components, the accuracy to which the various components are made and contemporary, normally used material and its manufacturing quality

= number of rows of rollers in a bearing

= nominal contact angle of the bearing, degrees

3. DEFINITIONS

For the purposes of this Standard, the definitions given in ANSVAFBMA Standard 1 together with the following apply.

3.1 Life

For an individual rolling bearing, the number of revolutions which one of the bearing rings (or washers) makes in relation to the other ring (or washer) before the first evidence of fatigue develops in the material of one of the rings (or washers) or rolling elements.

3.2 Reliability (in the context of bearing life)

For a group of apparently identical rolling bearings, operating under the same conditions, the percentage of the group that is expected to attain or exceed a specified life.

The reliability of an individual rolling bearing is the probability that the bearing will attain or exceed a specified life.

3.3 Static Load

The load acting on a bearing when the speed of rotation of its rings in relation to each other is zero.

3.4 Pitch Diameter of a Roller Set, D,,

The diameter of the circle intersecting the roller axes at the middle of the rollers in one row in a bearing.

3.5 Basic Rating Life, L,,

For an individual rolling bearing, or a group of apparently identical rolling bearings operating under the same conditions, the life associated with 90% reliability, with contemporary, commonly used material

and manufacturing quality, and under conventional operating conditions.

3.6 Adjusted Rating Life, L,,

The rating life obtained by adjustment of the basic rating life for a desired reliability level, special bearing properties and specific operating conditions.

3.7 Basic Dynamic Radial Load Rating, C,

That constant stationary radial load which a rolling bearing could theoretically endure for a basic rating life of one million revolutions.

3.8 Basic Static Radial Load Rating, C,,

Static radial load which corresponds to a calculated contact stress at the center of the most heavily loaded rolling element/ raceway contact of

- 4000 MPa (580,000 psi).

NOTE: For this contact stress, a total permanent deformation of rolling element and raceway occurs which is approximately 0.0001 of the rolling element diamater.

3.9 Basic Dynamic Axial Load Rating, C,

That constant centric axial load which a rolling bearing could theoretically endure for a basic rating life of one million revolutions.

3.10 Basic Static Axial Load Rating, C,,

Static centric axial load which corresponds to a calculated contact stress at the center of the most heavily loaded rolling element/raceway contact of

- 4000 MPa (580,000 psi) for thrust roller bearings.

NOTE: For this contact stress, a total permanent deformation of rolling element and raceway occurs which is approximately 0.0001 of the rolling element diameter.

3.11 Dynamic Equivalent Radial Load, P,,

That constant stationary radial load under the influence of which a rolling bearing would have the same life as it will attain under the actual load conditions.

3.12 Static Equivalent Radial Load, P,,

Static radial load which would cause the same contact stress at the center of the most heavily loaded rolling element/raceway contact as that which occurs under the actual load conditions.

3.13 Dynamic Equivalent Axial Load, P,

That constant centric axial load under the influence of which a rolling bearing would have the same life as it will attain under the actual load conditions.

3.14 Static Equivalent Axial Load, P,,

Static centric axial load which would cause the same contact stress at the center of the most heavily loaded rolling element/ raceway contact as that which occurs under the actual load conditions.

3.15 Roller Diameter Applicable in the Calculation of Load Ratings, D,,

The diameter at the middle of the roller.

NOTE: For a tapered roller this is equal to the mean value of the diameters at the theoretically sharp corners at the large end and at the small end of the roller.

For an asymmetrical convex roller this is an approximation of the diameter at the point of contact between the roller and the ribless raceway at zero load.

3.16 Roller Length Applicable in the Cal- culation of Load Ratings, L,

The theoretical maximum length of contact between a roller and that raceway where the contact is shortest.

NOTE: This is normally taken to be either the distance between the theoretically sharp corners of the roller minus the roller chamfers or the raceway width excluding the grinding undercuts, whichever is the smaller.

3.17 Nominal Contact Angle, cx

The angle between a plane perpendic- ular to the bearing axis and the nominal line of action of the resultant of the forces transmitted by a bearing ring to a rolling element.

3.18 Line Contact

“Line contact” refers to rollers and race ways so formed that under no load and when in good alignment they contact along the full length of their basic form.

3.19 Point Contact

“Point contact” refers to rollers and raceways so formed that under no load and when in good alignment they contact at a point located approximately at the middle of the rollers.

3.20 Optimized Contact

“Optimized contact” refers to such design of the basic form of the rollers and/or ring raceways that under a bearing load somewhere in the range of 25% to 50% of the basic dynamic radial load rating C,, the material stress is substantially uniform along the entire effective length of the contact at the most heavily loaded roller. Ide- ally, roller bearings are designed to ap- proach optimized contact.

3.21 Conventional Operating Condi- tions

Conditions which may be assumed to prevail for a bearing which is properly mounted and protected from foreign matter, normally lubricated, conventionally loaded, not exposed to extreme temperature and not run at low or high speed.

4. SCOPE

4.1 Bearing Types

4.1 .I General. Roller bearings covered by this standard are presumed to be within the size ranges shown in the ANSVAFBMA dimensional standards, manufactured of good quality hardened steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of rolling contact surfaces. Since small differences in relative shape of con- tacting surfaces may account for distinct differences in load carrying ability, this standard does not attempt to cover all design variations, rather it applies to basic roller bearing designs.

4.1.2 Basic Types. This standard ap-

4

.

plies to cylindrical, spherical, and tapered roller bearings, self-aligning radial roller bearings and to needle roller bearings.

4.1.3 Double Row. Double row radial roller bearings and double direction thrust roller bearings, as specified by this standard, are presumed to be symmetrical.

4.2 Limitations

4.2.1 Truncated Contact Area. This ‘standard may not be safely applied to roller bearings subjected to loading which causes the contact area of the roller with the raceway to be truncated by the edge of the raceway or roller. This limitation depends strongly on details of bearing design which are not standardized.

4.2.2 Materials. This standard applies to roller bearings made from hardened, good quality bearing steel. While a complete me- tallurgical description is beyond the scope of this standard, typical cleanliness and material composition specifications for bearing quality steel are given in ASTM A 295 and A 485 for through hardening steels, and in ASTM A 534 for carburizing steels. Typical hardness levels range from HRC 58 to 64 for rings or washers and HRC 60 to 65 for rollers.

4.2.3 Bearing Types. The f,, factors specified in basic load rating formulae are valid only for those roller bearing configu- rations specified in section 4.1 above. This standard is not applicable to designs where the rolling elements operate directly on a shaft or housing surface, unless that surface is equivalent in all respects to the bearing ring (or washer) raceway it re- places.

4.2.4 Lubrication. Basic rating life calculated according to this standard is based on the assumption that the bearing is adequately lubricated. Determination of adequate lubrication depends upon the bearing application. An adequate amount of an appropriate type of lubricant is essential to achieving expected performance. The Iu- bricant must be free of excessive contam- inants and of a viscosity level that will pro- vide a film thickness somewhat greater

than the rolling contact surfaces composite roughness at the operating temperature.

4.2.5 Ring Support and Alignment. Basic rating life calculated according to this standard assumes that the bearing inner and outer rings are rigidly supported, and that the inner and outer ring axes are properly aligned. Bearing rings (or washers) must be mounted so that any deformation of rings as a result of mounting compliance is small compared to contact deformation under the applied load.

4.2.6 Internal Clearance. Radial roller bearing basic rating life calculated according to this standard is based on the assumption that only a nominal internal clearance occurs in the mounted bearing at operating speed, load and temperature.

4.2.7 High Speed Effects. Basic rating life calculated according to this standard does not account for high speed effects such as roller centrifugal forces and gy- roscopic moments. These effects tend to diminish fatigue life. Analytical evaluation of these effects frequently requires the use of high speed digital computation devices and hence, cannot be included herein.

4.2.8 Stress Concentrations. A roller bearing must be expected to have a basic load rating less than that obtained using a value of f,, taken from Table 1 if, under load a stress concentration is present in some part of the roller-raceway contact. Such stress concentrations occur in the center of nominal point contacts, at the contact extremities for line contacts and at inade- quately blended junctions of a rolling surface profile. Stress concentrations can also occur if the rollers are not accurately guided such as in bearings without cages and bearings not having rigid integral flanges. Values of f,, given in Tables 1, 4, 5 and 6 are based upon bearings manufactured to achieve optimized contact. For no bearing type or execution will the factor f,, be greater than that obtained in Table 1, 4, 5 or 6 as appropriate.

4.2.9 Tolerances. This standard applies to cylindrical and spherical radial roller bearings and self-aligning radial roller

5

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bearings made to RBEC 1 level of precision or better commensurate with ANSUAFBMA Standard 20, to tapered radial roller bearings covered by ANSI/AFBMA Standards 19.1 and 19.2, to needle radial roller bearings covered by ANSI/AFBMA Standards 18.1 and 18.2, to thrust needle roller bearings covered by ANSI/AFBMA Standards 21.1 and 21.2, tapered roller thrust bearings covered by ANSI/AFBMA Standard 23.2, and to cylindrical and spherical roller thrust bearings covered by ANSI/AFBMA Standards 24.1 and 24.2.

4.2.10 Plastic Deformation in the Con- tact Area. If P, > 0.5C,, then plastic deformation may occur in the contact area. The user should consult the bearing manufacturer for recommendations and evaluation of equivalent load and life.

4.3 Operating Parameter+

Calculations according to this standard do not yield satisfactory results for bearings subjected to such application conditions which cause deviations from a normal load distribution in the bearing, for example mis- alignment, housing or shaft deflection, rolling element centrifugal forces or other high speed effects, and preload or extra large clearance in radial bearings. Where there is reason to assume that such conditions prevail, the user should consult the bearing manufacturer for recommendations and evaluation of equivalent load and life.

5. RADIAL ROLLER BEARINGS

5.1 Basic Dynamic Radial Load Rating

The basic dynamic radial load rating, C,, for a radial roller bearing is:

C, = f,,(iL,, COS~)~‘~Z~‘~D~~~

Values of f,, are obtained from the appropriate column of Table 1. They are maximum values, only applicable to roller bearings in which, under a bearing load, the material stress is substantially uniform along the most heavily loaded roller/raceway contact.

Smaller values of f,, than those given in table 1 should be used if, under load, an accentuated stress concentration is pres-

ent in some part of the roller/raceway contact. Such stress concentrations must be expected, for example, at the center of nominal point contacts, at the extremities of line contacts, in bearings where the rollers are not accurately guided and in bearings with rollers longer than 2.5 times the roller diameter.

5.1 .I Bearing Combinations

5.1.1 .I When calculating the basic radial load rating for two similar single row roller bearings mounted side-by-side on the same shaft such that they operate as a unit (paired mounting), in “back-to-back” or “face-to- face” arrangement, the pair is considered as one double row angular contact bearing.

5.1.1.2 If, for some technical reason, the bearing arrangement is regarded as two bearings which are replaceable independently of each other, then 5.1 .I .I does not apply.

5.1 .I .3 The basic radial load rating for two or more similar single row roller bearings mounted side-by-side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, properly manufactured and mounted for equal load distribution, is the number of bearings to the power of 7/9, times the rating of one single row bearing.

5.1.1.4 If, for some technical reason, the bearing arrangement is regarded as a number of single row bearings which are replaceable independent of each other, then 5.1 .I .3 does not apply.

5.2 Dynamic Equivalent Radial Load

The dynamic equivalent radial load, P,, for radial roller bearings, under constant radial and axial loads, is given by

P, = XF, + YF,

Values of X and Y are given in Table 2

The dynamic equivalent radial load for radial roller bearings with (Y = O”, and subjected to radial load only, is given by

P, = F,

NOTE: The ability of radial roller bearings

6

TABLE 1. Part 1 - Metric Values for f,, for Radial Roller Bearings’) Cylindrical Roller Bearings,

D,coscx*’ Tapered Roller Bearings Drawn Cup

and Needle Roller Bearings Needle Roller D PW with Machined Rings Bearings

0.01 57.310 52.100 0.02 66.880 60.800 0.03 73.150 66.500 0.04 77.770 70.700 0.05 81.510 74.100

0.06 84.590 76.900 0.07 87.120 79.200 0.08 89.210 81.100 0.09 91.080 82.800 0.10 92.620 84.200

0.11 93.830 85.300 0.12 95.040 86.400 0.13 95.810 87.100 0.14 96.470 87.700 0.15 97.020 88.200

0.16 97.350 88.500 0.17 97.570 88.700 0.18 97.680 88.800 0.19 97.680 88.800 0.20 97.570 88.700

0.21 97.350 88.500 0.22 97.020 88.200 0.23 96.580 87.800 0.24 96.250 87.500 0.25 95.590 86.900

0.26 95.040 86.400 0.27 94.380 85.800 0.28 93.720 85.200 0.29 92.840 84.400 0.30 92.070 83.700

0.31 91.300 83.000 0.32 90.420 82.200 0.33 89.430 81.300 0.34 88.440 80.400 0.35 87.450 79.500

0.36 86.460 78.600 0.37 85.360 77.600 0.38 84.370 76.700 0.39 83.270 75.700 0.40 82.060 74.600

0.41 80.960 73.600 0.42 79.750 72.500 0.43 78.540 71.400 0.44 77.330 70.300 0.45 76.120 69.200

0.46 74.910 68.100 0.47 73.700 67.000 0.48 72.380 65.800 0.49 71.060 64.600 0.50 69.850 63.500

' Use to obtain C, in newtons when D,.,, and D,, are given in miffimetres.

'Values of f,, for intermediate values of D,,cosa ~ are obtained by linear interpolation. D

PW

Spherical Roller Bearings

59.915 69.920 76.475 81.305 85.215

88.435 91.080 93.265 95.220 96.830

98.095 99.360 100.165 100.855 101.430

101.775 102.005 102.120 102.120 102.005

101.775 101.430 100.970 100.625 99.935

99.360 98.670 97.980 97.060 96.255

95.450 94.530 93.495 92.460 91.425

90.390 89.240 88.205 87.055 85.790

84.640 83.375 82.110 80.845 79.580

78.315 77.050 75.670 74.290 73.025

TABLE 1. Part 2 - Inch Values for f,, for Radial Roller Bearings’)

D,cosa”

-

D PW 0.01 0.02 0.03 0.04 0.05

0.06 7600 6909 7945 0.07 7828 7116 8183 0.08 8016 7287 8380 0.09 8184 7440 8556 0.10 8322 7565 8700

0.11 8431 7665 8814 0.12 8539 7763 8927 0.13 8609 7826 9000 0.14 8668 7880 9062 0.15 a718 7925 9114

0.16 8747 7952 9145 0.17 8767 7970 9166 0.18 8778 7979 9176 0.19 8778 7979 9176 0.20 8767 7970 9166

0.21 8747 7952 9145 0.22 8718 7925 9114 0.23 8678 7889 9073 0.24 8648 7862 9041 0.25 8589 7808 8980

0.26 8539 7763 8927 0.27 8480 7709 8865 0.28 8421 7655 8803 0.29 8342 7584 8721 0.30 8273 7521 8649

0.31 8204 7458 8577 0.32 8125 7386 8494 0.33 8036 7305 8401 0.34 7946 7224 8308 0.35 7857 7143 8214

0.36 7768 7062 8121 0.37 7669 6972 8018 0.38 7580 6891 7925 0.39 7482 6802 7822 0.40 7373 6703 7708

0.41 7274 6613 7605 0.42 7165 6514 7491 0.43 7057 6415 7377 0.44 6948 6316 7263 0.45 6840 6218 7151

Cylindrical Roller Bearings, Tapered Roller Bearings

and Needle Roller Bearings with Machined Rings

5149 6009 6573 6987 7324

Drawn Cup Needle Roller

Bearings

4681 5463 5975 6352 6658

0.46 6731 0.47 6622 0.48 6503 0.49 6384 0.50 6276

' Use to obtain Gin pounds when 0, and D,, are given in inches.

6119 7037 6020 6923 5912 6799 5804 6675 5705 6561

'Values of f,, for intermediate values of D,.cosa ___ are obtained by linear interpolation. D

!Jw

Spherical Roller Bearings

5383 6282 6871 7305 7657

a

TABLE 2. Values of X and Y for Radial Roller Bearings

5 pe

F. rye

Bearing Type X Y XI Y e

Single row, (Y f 0” 1 0 0.4 0.4cotCY 1.5tam Double row, (Y f 0” 1 0.45cota 0.67 0.67cota 1.5tanu

with (X = 0” to support axial loads varies considerably with bearing design and execution. The bearing user should therefore consult the bearing manufacturer for recommendations regarding the evaluation of equivalent load and life in cases where bearings with (X = 0” are subjected to axial load.

52.1 Bearing Combinations

5.2.1.1 When calculating the equivalent radial load for two similar single row roller bearings mounted side-by-side on the same shaft such that they operate as a unit (paired mounting) in “back-to-back” or “face-to- face” arrangement, and which, according to 5.1.1.1, is considered as one double row roller bearing, the values of X and Y for double row bearings given in Table 2 should be used.

5.2.1.2 When calculating the equivalent radial load for two or more similar single row roller bearings mounted side-by-side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, the values of X and Y for a single row bearing given in Table 2 shall be used.

5.3 Basic Rating Life

5.3.1 The basic rating life, L,,, for a radial roller bearing is given by

/CA ‘o’3 L 2 10 =

I I P,

The values of C, and P, are calculated in accordance with 5.1 and 5.2.

This life formula is also used for the evaluation of the life of two or more single row bearings operating as a unit, as referred to in 5.1 .I. In this case, the load rating C, is calculated for the complete bearing arrangement and the equivalent load P, is calculated for the total loads acting on the

arrangement, using the values of X and Y indicated in 5.2.1.

53.2 The life formula gives satisfactory results for a broad range of bearing loads. However, extra-heavy loads may cause detrimental plastic deformations at the rolling element/raceway contacts. The user should therefore consult the bearing manufacturer to establish the applicability of the life formula in cases where P, exceeds 0.5 c,.

5.4 Basic Static Radial Load Rating

The basic static radial load rating for radial roller bearings is given by the formula

D,, cosa D ~ZL,,D,,coscu (metric)

PW

- F iZL,,D,,coscx (inch) PW >

5.4.1 Bearing Combinations

5.4.1.1 The basic static radial load rating for two similar single-row roller bearings mounted side by side on the same shaft such that they operate as a unit (paired mounting) in “back-to-back” or “face-to-face” arrangement is twice the rating of one single row bearing.

5.4.1.2 The basic static radial load rating for two or more similar single-row roller bearings mounted side by side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, properly manufactured and mounted for equal load distribution, is the number of bearings times the rating of one single-row bearing.

5.5 Static Equivalent Radial Load

The static equivalent radial load for roller bearings is the greater of the two values given by the formulae

P,, = X,F, + Y,F,

Pm = Fr where the values of factors X, and Y, are given in Table 3.

9

TABLE 3. Values for Factors X, and Y, for Radial Roller Bearings with (x # 0” Bearing Type X0 Yo Single-row 0.5 0.22cota Double-row 1 0.44cota

for CY = 90”: C, = fcmL~~Z3’4D$‘27

for OL $1 90”:

C, = f,,(L,,coscx)7’gZ3’4D~?7tan~

where

The static equivalent radial load for radial roller bearings with (Y = O”, and subjected to radial load only, is given by the formula

Pm = Fr

NOTE: The ability of radial roller bearings with (Y = 0” to support axial loads varies considerably with bearing design and execution. The bearing user should therefore consult the bearing manufacturer for recommendations regarding the evaluation of equivalent load in cases where bearings with QL = 0” are subjected to axial load.


5.5.1.1 When calculating the static equivalent radial load for two similar single- row roller bearings mounted side by side on the same shaft such that they operate as a unit (paired mounting) in “back-to- back” or “face-to-face” arrangement, the X0 and Y, values for a double-row bearing and the F, and F, values for the total loads on the arrangement shall be used.

5.5.1.2 When calculating the static equivalent radial load for two or more similar single-row roller bearings mounted side by side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, the X0 and Y, values for a single-row bearing and the F, and F, values for the total loads on the arrangement shall be used.

6. THRUST ROLLER BEARINGS

6.1 Basic Dynamic Axial Load Rating

Z is the number of rollers carrying load in one direction.

6.1.1.2 If several rollers, on the same side of the bearing axis, are located with their axes coinciding, these rollers are considered as one roller with a length L,, equal to the sum of the lengths of the several rollers.

Values off,, are given in Tables 4, 5 and 6. They are maximum values, only applicable to roller bearings in which, under a bearing load, the material stress is substantially uniform along the most heavily loaded roller/raceway contact.

Smaller values of f,, than those given in Tables 4, 5 and 6 should be used if, under load, an accentuated stress concentration is present in some part of the roller/raceway contact. Such stress concentrations must be expected, for example, at the center of nominal point contacts, at the extremities of line contacts, in bearings where the rollers are not accurately guided and in bearings with rollers longer than 2.5 times the roller diameter.

Smaller values of f,, should also be considered for thrust roller bearings in which the geometry causes excessive slip in the roller/raceway contact areas, for example bearings with cylindrical rollers which are long in relation to the pitch diameter of the roller set.

6.1.2 Bearings with Two or More Rows of Rollers. The basic dynamic axial load rating for thrust roller bearings with two or more rows of similar rollers carrying load in

6.1.1 Single Row Bearings the same direction is given by

6.1.1.1 A thrust roller bearing is con- c, = (Z,L,,, + Z2Lwe* + + Z,L,,“) sidered as a single row bearing only if all rollers carrying load in the same direction contact the same washer raceway area.

x[($y+(~)-;l+,,,

The basic dynamic axial load rating, C,, - 219

for single row, single or double direction . thrust roller bearings is

IO

TABLE 4. Part 1 - Metric Values for f,, for Tapered Roller Bearinas’)

TABLE 4. - Inch Values for

lw2’ D prr 3.01 3.02 3.03 3.04 3.05

0.06 0.07 0.08 0.09 0.10

0.11 0.12 0.13 0.14 0.15

0.16 0.17 0.1E 0.16 0.2c

0.21 0.2; 0.2: 0.2L 0.25

0.22 0.2i 0.2t 0.2: 0.3(

= 90”

115.94 135.19 147.95 157.74 165.77

I,,COS& D pw 0.01 0.02 0.03 0.04 0.05

: = 50”3’ : = 65”4:

120.67 117.81 140.58 137.17 153.45 149.82 163.13 159.17 170.72 166.65

172.59 0.06 176.99 172.70 178.64 0.07 182.16 177.76 183.92 0.08 186.45 182.05 i 88.87 0.09 190.08 185.57 193.27 0.10 193.05 188.54

197.45 0.11 195.58 190.96 201.30 0.12 197.67 192.94 204.93 0.13 199.21 194.48 208.34 0.14 200.53 195.69 211.53 0.15 201.41 196.68

214.61 0.16 202.07 197.23 217.47 0.17 202.40 197.56 220.33 0.18 202.51 197.67 222.97 0.19 202.40 197.56 225.50 0.20 202.07 197.23

227.92 0.21 201.52 230.34 0.22 200.86 232.65 0.23 199.98 234.85 0.24 198.99 236.94 0.25 197.78

239.03 0.26 241.01 0.27 242.99 0.28 244.97 0.29 246.73 0.30

196.57 - - -

- - -

-

- -

-

0 - I ’ CY = 80+

116.16 135.30 147.73 157.08 164.34

170.39 175.34 179.52 183.04 185.90

188.32 190.30 191.84 193.05 193.93

- - - - -

- - - - -

- - - - -

’ Use to obtain C, in newtons when D,, and D,, are given in millimetres.

D,,cosa 2 Values of fcm for intermediate values of F or 7 are

PW PVJ obtained by linear interpolation.

3 Applicable for 45” < 01 < 60”. 4 Applicable for 60” 5 (Y < 75”. ’ Applicable for 75” 5 (Y < 90”.

The load ratings C,;, Ca2, . . , C,, for the rows with Z,, Z,, ., Z, rollers of lengths I- wel, Le2, , Lv,", are calculated from the appropriate single row bearing formula given in 6.1.1.


6.1.3.1 The basic axial load rating for two or more similar single direction thrust roller bearings mounted side-by-side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, properly manufactured and mounted for equal load distribution, is the

Dwe2’ D DW

0.01 10400 0.02 12127 0.03 13271 0.04 14149 0.05 14870

L.cosa2 D pvr 0.01 0.02 0.03 0.04 0.05

: = 50”3’

10824 12610 13764 14633 15314

y = 65”4

10568 12304 13439 14278 14949

< = 8f3-i

10420 12136 13251 14090 14741

0.06 15481 0.06 15876 15491 15284 0.07 16024 0.07 16340 15945 15728 0.08 16498 0.08 16725 16330 16103 0.09 16942 0.09 17050 16646 16419 0.10 17336 0.10 17317 16912 16675

0.11 17711 0.11 17544 17129 16892 0.12 18057 0.12 17731 17307 17070 0.13 18382 0.13 17869 17445 17208 0.14 18688 0.14 17988 17553 17317 0.15 18974 0.15 18066 17642 17396

0.16 19251 0.16 18126 17692 0.17 19507 0.17 18155 17721 0.18 19764 0.18 18165 17731 0.19 20000 0.19 la155 17721 0.20 20227 0.20 18126 17692

0.21 20444 0.21 18076 - 0.22 20661 0.22 18017 - 0.23 20869 0.23 17938 - 0.24 21066 0.24 17849 - 0.25 21254 0.25 17741 -

0.26 21441 0.26 17632 0.27 21619 0.27 -_ 0.28 21796 0.28 -_ ‘ 0.29 21974 0.29 -_ 0.30 22132 0.30 --

- - - - -

I,, and C

- - - - -

- - - - -

- - - -

’ Use to obt: C, in pounds when IC in inches.

D,,COSW ’ Values of f,, for intermediate values of + or ~ are

PW D PW obtained by linear interpolation.

3 Applicable for 45” < (Y < 60”. 4 Applicable for 60” % (Y < 75”. 5 Applicable for 75” 5 CK < 90”.

Ta Part 2 .pered

Y = 90

Bearings’)

c

f cm for

number of bearings to the power of 7/9, times the rating of one bearing.

6.1.3.2 If, for some technical reason, the bearing arrangement is regarded as a number of single direction bearings which are replaceable independently of each other, then 6.1.3.1 does not apply.

6.2 Dynamic Equivalent Axial Load

The dynamic equivalent axial load, P, for thrust roller bearings with cx = 90”, under constant radial and axial loads, is given by

11

TABLE 5. Part 1 - Metric Values for f,, for Cylindrical Roller Bearings and

Needle Roller Bearinas’)

3.01 105.4 0.01 109.7 3.02 122.9 0.02 127.8 0.03 134.5 0.03 139.5 0.04 143.4 0.04 148.3 0.05 150.7 0.05 155.2

0.06 156.9 0.06 160.9 0.07 162.4 0.07 165.6 0.08 167.2 0.08 169.5 0.09 171.7 0.09 172.8 0.10 175.7 0.10 175.5

0.11 179.5 0.11 177.8 0.12 183.0 0.12 179.7 0.13 186.3 0.13 181.1 0.14 189.4 0.14 182.3 0.15 192.3 0.15 183.1

0.16 195.1 0.16 183.7 0.17 197.7 0.17 184.0 0.18 200.3 0.18 184.1 0.19 202.7 0.19 184.0 0.20 205.0 0.20 183.7

0.21 207.2 0.21 183.2 0.22 209.4 0.22 182.6 0.23 211.5 0.23 181.8 0.24 213.5 0.24 180.9 0.25 215.4 0.25 179.8

0.26 217.3 0.27 219.1 0.28 220.9 0.29 222.7 0.30 224.3

0.26 178.7 - - - - - -

173.6 171.2 175.4 173.0 176.8 174.4 177.9 175.5 178.8 176.3

179.3 - 179.6 - 179.7 - 179.6 - 179.3 -

- - - -

- I - - -

- -

- - - - - - - - - -

' Use to obtain C, in newtons when D,, and D,, are given .in millimetres.

D,,coscu * Values of fcm for intermediate values of sorr are

PW PW obtained by linear interpolation.

3Applicable for 45" < cx < 60". 4 Applicable for 60" 5 (Y < 75". *Applicable for 75" 5 c1 < 90".

P, = X F, + Y F,

Values of X and Y are given in Table 7.

Thrust roller bearings with (X = 90” can support axial loads only. The dynamic equivalent axial load for this type of bearing is given by

P, = F,

6.3 Basic Rating Life

6.3.1 The basic rating life, L,,, for a thrust roller bearing is given by

TABLE 5. Part 2 - Inch Values for f,, for Cylindrical Roller Bearings and Needle

r D 2' we D pw 0.01 0.02 0.03 0.04 0.05

Roller Bearings’) r

9454 0.01 11024 0.02 12065 0.03 12863 0.04 13518 0.05

[ = 50”3’ L = 65-

9840 9607 11464 11186 12513 12217 13303 12980 13921 13590

y = 8()“*’

9472 11033 12047 12809 13401

0.06 14074 0.06 14433 14083 13895 0.07 14567 0.07 14854 14496 14298 0.08 14998 0.08 15204 14845 14639 0.09 15401 0.09 15500 15132 14926 0.10 15760 0.10 15742 15375 15159

0.11 16101 0.11 15949 15572 15357 0.12 16415 0.12 16119 15733 15518 0.13 16711 0.13 16245 15859 15644 0.14 16989 0.14 16352 15958 15742 0.15 17249 0.15 16424 16038 15814

0.16 17500 0.16 16478 16083 0.17 17734 0.17 16505 16110 0.18 17967 0.18 16514 16119 0.19 18182 0.19 16505 16110 0.20 18389 0.20 16478 16083

- - -

0.21 18586 0.21 16433 0.22 18783 0.22 16379 0.23 18972 0.23 16307 0.24 19151 0.24 16227 0.25 19321 0.25 16128

- - -

0.26 19492 0.26 0.27 19653 -

0.28 19815 -

0.29 19976 -

0.30 20120 -

16029 - - - -

- - - - -

- - - - -

-

- - - - -

' Use to obti ,&in pounds wher rwe and U,, are grven in inches.

D,.&oso( 'Values offc, for intermediate values of For-D-- are

PW PW obtained by linear interpolation.

3 Applicable for 45" < (Y < 60". 'Applicable for 60" 5 (Y < 75". 'Applicable for 75" 5 (Y < 90".

0 1013

L,, = $ a

The values of C, and P, are calculated in accordance with 6.1 and 6.2.

This life formula is also used for the evaluation of the life of two or more single direction thrust roller bearings operating as a unit, as referred to in 6.1.3. In this case, the load rating C, is calculated for the complete bearing arrangement and the equivalent load P, is calculated for the total loads

12

.- TABLE 6. Part 1 - Metric Valuesior f,,

),2’ D -!Y 1.01 1.02 1.03 3.04 3.05

3.06 D.07 0.08 0.09 0.10

0.11 0.12 0.13 0.14 0.15

0.16 0.17 0.16 0.1s 0.2c

0.21 0.2; 0.2: 0.21 0.2E

0.22 0.2: 0.2t 0.2; 0.3(

'C

I

I.3

lllir in ml

i

for S

121.210 141.335 154.675 164.910 173.305

180.435 186.760 192.280 197.455 202.055

206.425 210.450 214.245 217.810 221.145

224.365 227.355 230.345 233.105 235.75C

238.28C 240.8lC 243.225 245.525 247.7lC

249.895 251.965 254.031 256.101 257.94:

: to obti metres.

#pherical Roller

b

0.01 0.02 0.03 0.04 0.05

,

, / p1

1

= 50-1 = 65”“’

126.155 123.165 146.970 143.405 160.425 156.630 170.545 166.405 178.480 174.225

= 80°5’

121.440 141.450 154.445 164.220 171.810

D. a-

L = 90’

10873 12678 13874 14792 15545

[ = 50"3' : = 69” : = 8()‘=’

11316 11048 10893 13183 12863 12688 14390 14050 13854 15298 14927 14731 16010 15628 15411

0.06 185.035 180.550 178.135 1.06 16185 0.06 16598 16195 15979 0.07 190.440 185.840 183.310 1.07 16752 0.07 17082 16670 16443 0.08 194.925 190.325 187.680 1.08 17248 0.08 I 7485 17072 16835 0.09 198.720 194.005 191.360 1.09 17712 0.09 17825 17402 17165 0.10 201.825 197.110 194.350 1.10 18124 0.10 18104 17681 17433

0.11 204.470 199.640 196.880 1.11 18516 0.11 18341 17908 17660 0.12 206.655 201.710 198.950 3.12 18877 0.12 18537 18093 17846 0.13 208.265 203.320 200.560 3.13 19218 0.13 18681 18238 17990 0.14 209.645 204.585 201.825 3.14 19538 0.14 18774 18351 18104 0.15 210.565 205.620 202.745 3.15 19837 0.15 18888 18444 18186

0.16 211.255 206.195 - 0.16 20126 0.16 18950 18496 0.17 211.600 206.540 - 0.17 20394 0.17 18981 18527 0.18 211.715 206.655 - 0.18 20662 0.18 18991 18537 0.19 211.600 206.540 - 0.19 20910 0.19 18981 18527 0.20 211.255 206.195 - 0.20 21148 0.20 18950 18496

0.21 210.680 0.22 209.990 0.23 209.070 0.24 208.035 0.25 206.770

- - -

-

- 0.21 21374 0.21 18898 - 0.22 21601 0.22 18836 - 0.23 21817 0.23 18754 - 0.24 22024 0.24 18661 - 0.25 22220 0.25 18547

0.26 - - - -

205.505 -

- -

- -

- - - - -

1, and I

- -

are given

0.2E 22416 0.26 18434 0.25 22601 - -

0.2E 22787 - -

0.2s 22973 - -

0.3c 23138 - -

- - - - -

- - - - -

- - - - -

- - - - -

- - - - -

&in newtons whs D PW

D D,,cosa *Values off,, forintermediatevalues of for------- are

ow D DW obtained by linear interpolation.

3 Applicable for 45" < CY < 60". “Applicable for 60" 5 o( < 75". 'Applicable for 75" 5 a < 90".

TABLE 7. Values of X and Y for Thrust Roller Bearings

5 < e s>e F, F,

Bearing Type X Y XY

Single direction, CY # 90" -1) -.-'I tancl 1

Double direction, a # 90" 1.5tancu 0.67 tancv 1 t

e

1.5tan~

l.Stana

' F < e is unsuitable for single direction bearings.

TABLE 6. Part 2 - Inch Values for f,, for Spherical Roller Bearinqs’) -’

I

' Use to obtain C, in pounds when D,, and D,, are given in inches.

D,,cosa 2 Values of f,, for intermediate values of +or ~ are

PW D PW obtained by linear interpolation.

'Applicable for 45" < (Y < 60". 4Applicable for 60" 5 (Y < 75". 'Applicable for 75" 5 a < 90".

acting on the arrangement, using the values of X and Y given for single direction bearings in 6.2.

6.3.2 The life formula gives satisfactory results for a broad range of bearing loads. However, extra-heavy loads may cause detrimental plastic deformations at the roller/raceway contacts. The user should therefore consult the bearing manufacturer to establish the applicability of the life formula in cases where P, exceeds 0.5 C,.

6.4 Basic Static Axial Load Rating

The basic static axial load rating for single-or double-direction thrust roller bearings is given by the formula

c,, = 220 1 D,,coscc

- 7 ZL,,D,,sina (metric) PW

C,, = 32150 i

1 - D,cosa

D ZL,D,,sina (inch) v+

where Z is the number of rollers carrying load in one direction.

In cases where rollers have different lengths, ZL,, is taken as the sum of the lengths, defined in 3.16, of all the rollers carrying load in one direction.

6.4.1 Bearing Combinations. The basic static axial load rating for two or more similar single-direction thrust roller bearings mounted side by side on the same shaft such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, properly manufactured and mounted for equal load distribution, is the number of bearings times the rating of one single-direction bearing.

6.5 Static Equivalent Axial Load

The static equivalent axial load for thrust roller bearings with OL # 90” is given by the formula

P,, = 2.3F,tan(u + F,

This formula is valid for all ratios of radial load to axial load in the case of double- direction bearings. For single-direction bearings, it is valid where F,/F, < 0.44 cota and gives satisfactory but less conserva- tive values of P,, for F,/F, up to 0.67 cota.

Thrust roller bearings with cx = 90” can support axial loads only. The static equivalent axial load for this type of bearing is given by the formula

Pm = Fa

6.5.1 Bearing Combinations. When calculating the static equivalent axial load for two or more similar thrust roller bearings mounted side by side on the same shaft

such that they operate as a unit (paired or stack mounting) in “tandem” arrangement, the F, and F, values for the total loads acting on the arrangement shall be used.

7. ADJUSTED RATING LIFE

7.1 General

It is often satisfactory to use the basic rating life, L,,, as a criterion of bearing performance. This life is associated with 90% reliability, with contemporary, commonly used material and manufacturing quality, and under conventional operating conditions.

However, for many applications it may be desirable to calculate the life for a different reliability and/or for special bearing properties and operating conditions which deviate from the conventional in such a way that it is justified to take their influence into special consideration.

The adusted rating life, L,,, i.e. the basic rating life adjusted for a reliability of (loo- n)%, for special bearing properties and for specific operating conditions, is given by

La = ala2a3L10

Values of a, are given in Table 8. Values of a2 and a3 are discussed in 7.4 and 7.5. The value of L10 is calculated in accordance with 5.3 and 6.3.

7.2 Limitations

In addition to the required fatigue life, other factors, such as maximum permissible bearing deflection and minimum shaft and housing strength, should be given due consideration when selecting the size of bearings for a given application. Particular discretion shall be exercised when using adjusted rating life values which are based on values of a2 and a3 greater than 1.

7.3 Life Adjustment Factor for Reliabil- ity, al

Reliability is defined in 3.2. The adjusted rating life is calculated in accordance with 7.1. Values of the life adjustment factor a, are given in Table 8.

14

TABLE 8. Life Adiustment Factor for Reliathty, a,

Reliability % L na al 90 95 96 97 98 99

1 0.62 0.53 0.44 0.33 0.21

7.4 Life Adjustment Factor For Special Bearing Properties, a2

7.4.1 A bearing may acquire special properties, as regards life, by the use of a special type and quality of material and/or special manufacturing processes and/or special design. Such special life properties are taken into account by the application of the life adjustment factor a2.

The present state of knowledge does not make it possible to define relationships between the values of a2 and quantifiable characteristics of the material or bearing raceway geometry, for example. The values of a2 have therefore to be based on experience, and may usually be obtained from the manufacturer of the bearing.

7.4.2 The use of a certain steel analysis and/or process as such is not sufficient jus- tification for the use of an a, value other than 1. Values of a2 greater than 1 may, however be applicable to bearings made of steel of particularly low impurity content or of special analysis. However, if a reduced life is expected because of a hardness reduction caused by special heat treatment, this should be considered by the selection of a correspondingly reduced a2 value.

7.4.3 A special design involving an in- creased or reduced uniformity of the stress in the contacts between rolling elements and raceways should also be considered in the selection of the value of a2.

7.4.4 It may not be assumed that the use of a special material, process or design will overcome a deficiency in lubrication. Values of a2 greater than 1 should therefore normally not be applied if a3 is less than 1 because of such deficiency.

7.5 Life Adjustment Factor For Operat- ing Conditions, a3

7.5.1 Of the operating conditions directly influencing bearing life, the direction and magnitude of the load are considered in the calculation of the equivalent load, (5.2, 5.5, 6.2 and 6.5), and deviations from normal load distribution are discussed in 1.3.

Operating conditions which remain to be taken into account here include the ade- quacy of the lubrication (at the operating speed and temperature), presence of foreign matter, conditions causing changes in material properties (for example high temperature causing reduced hardness) and mounting conditions. The influence on bearing life of such conditions may be taken into account by the introduction of a life adjustment factor as.

7.5.2 The calculation of basic rating life in this standard assumes that the lubrication is normal, i.e. that the lubricant film in the rolling element/raceway contacts has a thickness which is equal to or slightly greater than the composite roughness of the contact surfaces. Where this require- ment is fulfilled, a3 is equal to 1, provided a lower value does not apply, for example because of a change in material properties caused by the operating conditions.

7.5.3 Values of a3 less than 1 should be considered, for example where the kine- matic viscosity of the lubricant, at the operating temperature, is less than 13 mm21 s’) for roller bearings and/or where the ro- tational speed is exceptionally low (i.e. D, in mm times revolutions per minute is less than 10,000).

Values of a3 greater than 1 may be considered only where the lubrication conditions are so favourable that the probability of fail- ure caused by surface distress is greatly reduced.

Manufacturers of bearings are expected to supply recommendations regarding appropriate values of a3 to be used in the calculation of adjusted rating life in accordance with 7.1.

’ 1 mm% = IcSt

15

American National Standards

The standard in this booklet is one of more than 10,000 standards approved to date by the American National Standards institute.

The Standards Institute provides the machinery for creating voluntary standards. It serves to eliminate duplication of standards activities and to weld conflicting standards into single, nationally accepted standards under the designation “American National Standards.”

Each standard represents general agreement among maker, seller, and user groups as to the best current practice with regard to some specific problem. Thus the completed standards cut across the whole fabric of production, distribution, and consumption of goods and services. American National Standards, by reason of Institute procedures, reflect a national consensus of manufacturers, consumers, and scientific, technical, and professional organizations, and governmental agencies. The completed standards are used widely by industry and commerce and often by municipal, state, and federal governments.

The Standards Institute, under whose auspices this work is being done, is the United States clearinghouse and coordinating body for voluntary standards activity on the national level. It is a federation of trade associations, technical societies, professional groups, and consumer organizations. Some 1000 companies are affiliated with the Institute as company members.

The American National Standards lnsitute is the United States member of the Inter- national Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). Through these channels U.S. standards interests make their posi- tions felt on the international level. American National Standards are on file in the libraries of the national standards bodies of more than 60 countries.

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New York, N.Y. 10018

ansi_afbma std 11-1990

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