SKF Roller Bearing Handbook.pdf

7/27/2019 SKF Roller Bearing Handbook.pdf

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SKF INDUSTRIES, INCBEARINGS GROUP

.


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SKF Industries Inc 1979

Although care has been taken to assure the accuracy of the datacomplied in this publication SKF does not assume any liability forerrors or omsslons

t

REG NO. 47


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ContentsThe History of Rolling Bearings . . . . . . . . . 2

Bearing Nomenclature . . . . . . . . . . . 4

Rolling Bearing Types . . . . D . e . . . D 5Bearing Types and their Function . . . . . . . . 6

Mounting of Bearings-Shaftsand Housings . . . . . 9Dos and Donts for Bearings . . . . . . . . . 14

Troubleshooting . . D , O s a r . . . O . 19

SKF Industries, Inc. periodically conducts BearingMaintenance Seminars at the Corporate Headquartersin King of Prussia, Pa. For information contact yourlocal authorized SKF Distributor or SKF Sales Office.


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THE HISTORY OF ROLLING BEARINGS

THE BASIC PRINCIPLES of design and application of roiling bearings were conceived many centuries ago. They were

developed for one purpose only--to lessen friction.

History records that down through the ages men desired to move heavy objects across the earths surface, Desired,

but not always achieved. Regardless of available manpower, sliding friction between the earths surface and the

object sometimes made it impossible.

Fig. 1 -Anti-fricfion odoptafion, I IO 0 B C--

Fig. 2-Early wheel, based on sliding friction

As far back as 1 100 B.C., we know that such friction was reduced

by the insertion of rollers between the object and the surface over

which it was being moved. Fig. 1 illustrates how, in 1 100 B.C., the

Assyrians and Babylonians used rollers to move enormous stones for

their monuments and palaces. Throughout history are recorded

many similar examples of mans war on friction.

In modern times, the first important victory over fric tion was the

invention of the wheel. However, the early wheel was based on

sliding friction (Fig. 2) and a long time elapsed before this principle

was refined. Later, wheels rendered friction a body blow when

they were rested on an assembly of balls or rollers. Cyc ling and

skating, which involved personal effort, boosted interest in rolling

bearings (Fig. 3)-and started long years of slow development.

Anyone who has tried to move a heavy object by sliding, readily

appreciates the ease with which it can be done when rollers are used.

Weight of the objec t is not a fac tor-as long as both the rolling

elements and the surfac e over which they pass can support itwithout being pressed out of shape.

Place a heavy book on a flat, smooth surface (Fig. 4) and as you

push it ac ross that surfac e, notice the amount of effort required.

This is sliding friction.

Fig. 3-Cycling boosted anti-friction interest Fig. 4-Sl id ing friction Fig. S-Rolling motion

2


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Now, place two round pencils under the book (Fig. 5). Note how easily

it can be moved. This is the difference between sliding friction and

rolling motion.

Fig. 6-Improved rolling mot ion

Fig. 7 - - B o o k bec ome s inne rr ing

brl-------...._------AFig. 8 - S u rf a c e be co me s outer ring

Fig. 9--Experiment illustrates bask bearing design

You will note that, when pushing the book with the pencils as rolling

elements, a tracking effect is present. The book can go forward orbackward with ease.

Now, substitute several balls for the rollers (Fig. 6), and note theadded ease with which the book moves. Also, note the fact that it

can be moved in one direction as easily as in another. These ad-

vantages are due to point contact provided by the balls, rather than

the line contact of the pencils.

In review - we noted that sliding the book on the surface requireda certain effort- that rolling it over the pencils required less effortbut that the direction was limited - and finally, when we substitutedthe balls, less effort was required and direction was unlimited.

The book, the surface and the pencils o r balls are the three im-

portant, basic parts of a ball or roller bearing.

If you performed this interesting experiment, you noted several im-

portant factors. First, that the book would run off the pencils and the

balls. Second, and this may not have been so apparent, that there

was a tendency for one roiling element not to follow or track

the same as the other rolling element. This was true of both pencils

and balls - but to a lesser degree in the bail experiment.Let us imagine that the book in Fig. 6 is curled into the position of

Fig. 7. The book is then the equivalent of the inner ring of a ball

bearing..

While our imagination is at play, picture the table surface of Fig. 6

curled into the position of Fig. 8 - and the balls in the positionillustrated.

Actually, we have converted our early experiment into a basic ball

bearing in design. The book becomes the inner ring - the surfacethe outer ring - and the balls the rolling elements (Fig. 9).This experiment, however, does not illustrate one other important

part of a bearing. You will recall that we noted that the pencils or

balls did not track - i.e., roll in the same direction, or keep thesame distance apart. For this reason the bearing requires a cage,

or retainer, to keep the rollers or balls in their proper position. In

tapered roller bearings the inner ring is called the cone, - theouter ring, the cup.

3


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BEARING NOMENCLATURE

The illustrations below identify the bearing parts of the eight SKF basic bearing types. The terms used conform

with the terminology section of the AFBMA* Standards+nd are mutually accepted bythe anti-friction bearing

manufacturers*Anti-Friction Bearing Manufacturers Association, Inc.

Self-Aligning

Ball Bearing

Single Row

Deep Groove

Bol l B e a r i n g

Double Row

Deep G r o o v e

Ball Bearing

Spheric01 RollerBearing

ETypeSpherical

Roller Thrust

1. Inner Ring

2. Inner Ring Corner

3. tnner Ring Loud4. Outer Ring Land

5. Outer Ring

6 . Ball7. Counter Bore8. Thrust Face

9. Outer Ring Raceway

10. Inner Ring Raceway

11. Outer Ring Corner

12. Spherical Roller

13. Lubrication Feature

(Hole and Groove) (W33)14. Spherical Outer Ring Raceway15. Floating Guide Ring16. Inner Ring Face

Cylindrkol Roller

ho r i n gTapered Roller

Beoring

Angular Contact

Bol l Bw r i n g

Spheric01 RollerThrustBearing

17. Outer Ring Face

18. Cylindrical Roller

19. Outer Ring Rib

20. C o n e F r o n t F a c e21. Cone Front Face Rib

22. Cup (Outer Ring)

23. Tapered Roller

24. Cone Rock Face Rib

25. Cone Bock Face2 6. U n d e r C u t

27. Cone (Inner Ring)

28. cage29. Cage

30. Face31. Cage Guide Sleeve

32. Shaft Washer (Inner Ring)

33. Housing Washer (Outer Ring)

4


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ROLLING BEARING TYPESBALL BEARINGS

Single Row Double Row Radial Thrust

Duplex Snap Ringand Shield

Shield Seal

Self-Aligning Magneto Front Wheel

SeparableOuter Ring

ROLLER BEARINGS

CylindricalRoller

SeparableInner Ring

CylindricalRollerNon-

separable

TapereRoller

Multi-Row Cylindrical Roller

.Spherical RollerThrust

Spherical RollerDouble Row

Needle Roll


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BEARING TYPES AND THEIR FUNCTIONS

Designers have a wide variety of bearing types from which to choose. Each bearing type has characteristics which

make it the best choice for a certain application. The original selection is made to assure maximum bearing perform-

ance. Therefore, a replacement should be made with the same type bearing, The following resume of the functionsof each bearing type will aid you to better serve your replacement field.

SELF-ALIGNING BALL BEARINGS

The Self-aligning Ball Bearing, with two rows of balls roiling on the spherical

surface of the outer ring, compensates for angular misalignment resulting

from errors in mounting, shaft deflection and distortion of the foundation. It is

impossible for this bearing to exert any bending influence on the shaft, a most

important consideration in applications requiring extreme accuracy, at high

speeds. Self-a ligning Ball Bearings are rec ommended for radial loads and

small thrust loads in either direction.

SINGLE ROW, DEEP GROOVE BALL BEARIYGS

The Single Row, Deep Groove Ball Bearing will sustain, in addition to radial

load, a substantial thrust load in either direction, even at very high speeds.

This advantage results from the intimate contact existing between the balls

and the deep, continuous groove in each ring. When using this type of bear-

ing, careful alignment between the shaft and housing is essential. This bearing

is also available with seals and shields, which serve to exc lude dirt and

retain lubricant.

ANGULAR CONTACT BALL BEARINGS

The Angular Contact Ball Bearing supports a heavy thrust load in one direction,

sometimes combined with a moderate radial load. A steep contact angle,

assuring the highest thrust capacity and axial rigidity, is obtained by a high

thrust supporting shoulder on the inner ring and a similar high shoulder an the

opposite side of the outer ring. These bearings can be mounted singly or, when

the sides are flush ground, in tandem for constant thrust in one direc tion;

mounted in pairs, also when sides are flush ground, for a combined load, either

face-to-face or back-to-back.

DOUBLE ROW, DEEP GROOVE BALL BEARINGS

The Double Row, Deep Groove Ball Bearing embodies the same principle of

design as the single row bearing. However, the grooves for the two rows ofballs are so positioned that the load lines through the balls have an out-

wardly converging contact angle. This bearing has a lower axial displace-

ment than occurs in the single row design . . . substantial thrust capacity in

either direc tion . . . and high radial capacity due to the two rows of balls.

6


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SPHERICAL ROLLER BEARINGS \

The Spherical Roller Bearing, due to the number, size and shape of the rolle

and the accuracy with which they are guided, has unexcelled capacity. Sin

the bearing is inherently self-aligning, angular misalignment between t

shaft and housing has no detrimental effect and the full capacity is alwa

available for useful work. The design and proportion are such that, in~additioto radial load, heavy thrust load may be carried in either direction.

CYLINDRICAL ROLLER BEARINGS

The Cylindrical Roller Bearing has high radial capacity and provides accura

guiding of the rollers, resulting in a close approach to true rolling. Conseque

low friction permits operation at high speed. Those types which have flang

on one ring only, allow a limited free axial movement of the shaft in relat

to the housing. They are easy to dismount even when both rings are mounte

with a tight fit. The double row type assures maximum radial rigidity and

particularly suitable for machine tool spindles.

SPHERICAL ROLLER THRUST BEARINGS

The Spherical Roller Thrust Bearing is designed to carry heavy thrust loads,

combined loads which are predominantly thrust. This bearing has a single ro

of rollers which roll on a spherical outer race with full self-alignment. The cage

centered by a cage guide sleeve, is constructed so that lubricant is pumped

directly against the inner rings unusually high guide flange. This insures goo

lubrication between the roller ends and the guide flange. The spherical roll

thrust bearing operates best with relatively heavy oil lubrication.

TAPERED ROLLER BEARINGS

Since the axes of its rollers and raceways.form an angle with the shaft axthe Tapered Roller Bearing is espec ially suitable for carrying radial an

axia l loads ac ting simultaneously. A bearing of this type usually must b

adjusted toward another bearing c apable of carrying thrust loads in t

opposite direction. Tapered Roller Bearings are separable-their con

(inner rings) with rollers and their cups (outer rings) are mounted separate


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OllP3Shield

Two OneShields Red Seal

Suffix 2 SufFix 22 Suffix RS

SHIELDS, SEALS AND SNAP RINGS

Tw oRed Seals

Sulfix 2RS

Ll l.lSna p Ring On Sna p Ring On Sna p Ring On Snap Ring On Snap Ring On

O uter Ring O uter Ring O n O uter Ring On Outer Ring On Outer Ring OnOpposite Side Some Side Opposite Side Same SideTo One Shie ld As One Shie ld To One Red Seal As One Red Seal

Suffix NR Suffix ZNR Suffix ZNBR Sut%x RSNR Suffix RSNBR

ANGULAR CONTACT BALL BEARINGS

IN DUPLEX MOUNTINGS

FACE-TO-FACE BACK-TO-BACK TANDEM

PARTS AND ASSEMBLY OF SIC F ADAPTER BEARINGS

Tapered Bore Bearing Adapter Mounting

8


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MOUNTING OF BEARINGS

-SHAFTS AND HOUSINGS

MOUNTING DESIGNS

The successful application of a ball or roller bearing

depends to a great degree on two factors:

l the mounting design

l the accuracy of the various machined surfaces

upon which the bearing is supported.

Unless care is exercised in both designing the bearing

mounting and machining the various parts, a prema-

ture failure may result. This is true, even though the

capacity of the bearing specified may be well above

the applied load.

The narrow width of a ball or roller bearing providesa comparatively small surface area for the applied

load. Hence, the unit pressures are high and must be

uniformly distributed to the supporting surfaces of both

the shaft and the housing. Therefore, it is evident that

both the inner and outer rings must be properly

mounted on the shaft and in the housing respectively.

Serious distortion is eliminated and uniform distribu-

tion of the Ioad is obtained.

This same care must also be used with respect to the

pedestal on which the bearing housing is mounted.

Distortion of the bearing housing will occur, unless the

pedestal is firm and the surface true.

A bearing housing should be designed to permit a

simplified assembly and disassembly of the component

parts. Such design should also provide for simple

methods of casting, with few mac hined surfaces-to

reduce costs to a minimum.

CLEANLINESS

The importanc e of protec ting the bearing from th

intrusion of dirt and other foreign matter cannot b

over emphasized. Seals must be designed to preve

the entranc e of any type of foreign matter to th

bearing. Dirt will act as a perfect lapping compoun

and will grind the bearing surfaces. This will result

excessive wear of the rolling elements and of the inn

and outer rings. In addition, foreign matter will co

taminate the lubricant-and gradually break dow

the oil or greose to the point where effective lubric

tion cannot be obtained. Dirt will also cause nois

operation.

The cavity in the housing around the bearing shou

be large enough to provide for an adequate amou

of lubricant. Seals should be effective in retaining th

lubricant in the housing.

MOUNTING AND DISMOUNTING

Bearings may be mounted directly on the shaft or o

tapered odapter sleeves.

When mounted direc tly on the shaft, the inner ri

should be located against a shaft shoulder of prop

height. Proper shaft shoulder heights are listed in t

Bearing Catalogs. This shoulder must be machine

square with the bearing seat and a shaft fillet shou

be used. The radius of the fillet must clear the corn

radius of the inner ring. This also applies whe

mounting the outer ring in the housing. General

Shaft filler Too Large Correct Shaft Fi l le t


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Shaft Shoulder Diameter Too Small Shaft Shoulder Diameter Too Large Correct Shaft Shoulder Diameter

speaking, bearing applications have a rotating inner

ring with a stationary load applied to the bearing. In

such cases, it is necessary to mount the inner ring with

a press fit on the shaft-and the outer ring with a slip

fit in the housing.

If the inner ring is loose on the shaft, creeping will

occur. This will result in overheating, excessive wear

and contact erosion between the shaft ond the inner

ring. The explanation of creeping action can be simpli-

fied by the use of this comparison. Compore the

action of on internal gear in mesh with a planet pinion.

If the planet pinion (representing the shaft), hod one

tooth less than the internal gear (representing the

bearing inner ring), the latter would slip back one geor

tooth in each full revolution of the shaft. Hence, the

speed of the shaft (planet gear) would be greater

than the speed of the inner ring (ring gear)-and

sliding would toke place.

Therefore, it is an obvious conclusion that a preventive

measure must be token to eliminate creeping and its

harmful results. Mount the inner ring with a sufficientpress fit on the shaft! This will insure that both inner

ring ond shaft act as a unit-and both rotate at the

same speed. It is also desirable to use a locknut to

clamp the inner ring agoinst the shaft shoulder.

If the opplied load is of a rototing nature, for example

-vibrating screens where unbalanced weights are

attached to the shaft, then the outer ring becomes the

critical member. In order to eliminate creeping in this

case, the outer ring must be mounted with a press fit

V-Belt ond Sprocket Drive, Resulting in Stationa ry Loa ds and Rotating Inne rRings

10


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in the housing. The rotating inner ring, when subjected to

a rotating load, can be mounted with a slip fit on the shaft

It is evident, therefore, thot when the applied load is sta-

tionary with respect to the outer ring, a tight shaft fit is

required When the applied load is stationary with respect

to the inner ring, a tight housing fit is required

Small bearings may be pressed on the shaft by using a pieceof tubing. Pressure is applied to the inner ring of the bearing

by the tubing. The assembly of larger open bearings can be

simplified by a heating procedure Boil the bearing in an

emulsion of 10% to 15% soluble oil in water. Make sure the

bearing is placed on a grating so it does not touch the sides

or bottom of the container Temperature control is automatic

but sufficient time should be allowed to assure that the bear-

ing is heated throughout This will sufficiently expand the

bearing and permit it to slide easily over the shaft to its

proper location Care should be taken to prevent cocking of

the inner ring as this may cause it to seize before the bearing

is properly located If this happens, it is best to remove the

bearing promptly and reheat When the bearing coots, it will

shrink and grip the shaft It requires only a little ingenuity to

provide the tools to facilitate this procedure

An electric hot plate or an induction heater can also be used

to heat an open beoring. Temperature should not exceed

121 C (250F) Assembly of sealed bearings can be accom-

plished by heating the bearing to a maximum of 107C

(225F) with either a hot plate or an induction heater and

proceed as mentioned above for mounting the bearing.

SHAFT AND HOUSING FITS

A ball or roller bearing has extremely accurate component

parts which fit together with very close clearances. The inner

ring bore and the outer ring outside diameter must be manu-

factured within close limiis to fit their respective supporting

members-the shaft and the housing It follows that the shaft

and housing must also be machined to close limits Only then,

will we obtain the required fits when the bearing is mounted.

It is advisable to refer to the tables of shaft and housing fits

as published in the SKF Engineering Data Catalog. These

tables list recommended dimensions and tolerances for vari-

ous types of shaft and housing fits suitable for various oper-

ating conditions.

ADAPTER SLEEVE

The use of a topered adapter sleeve on standard shafting

will greatly simplify the mounting of the bearing. The outer

surface of the sleeve is tapered to match the tapered bore

of the beoring inner ring. This will provide the required tight

fit between the inner ring and the shaft The adapter sleeve

is slotted to permit easy contraction and is threaded at the

small end to fit a locknut When the locknut is tightened to

the recommended Reduction in Internal Radial Looseness, the

correct interference between inner ring and shaft is achieved.

A lockwasher between the inner ring and the locknut p

vents the nut from loosening. The use of micronized graph

will greatly fac ilitate assembly-and help prevent conta

erosion of the parts A light coating of graphite is appli

on the 0.D adapter sleeve. It is good practice to apply

coat. of oil to the housing and component parts before th

bearing unit is assembled.

INTERNAL BEARING FITS

It is evident that a press fit between the parts will stretch t

inner ring. This holds true when mounting the bearing direct

on the shaft or by means of an adapter sleeve. Thus, ther

will be a tendency to reduce the initial internal radial cle

ance in the bearing.

If an excessive press fit is used, it is possible to reduce

bearing clearance sufficiently to make the bearing tight.

However, if the recommended shaft fits are used and oper

ing temperatures have been taken into account, the intern

clearance remaining after mounting the bearing will be su

cient to insure proper operation.

When an adapter mounting is used, some additional cautio

should be heeded If these are taken into consideration, t

bearing will not be tight internally.

The following is the recommended practice for mounting s

aligning ballbearings on adapters. Mount bearing on ada

ter sleeve, starting with the large bore of the inner ring

match the taper of the adapter. With the bearing hand tigh

on the adapter, locate bearing to the proper axial positi

on the shaft [Do not apply lockwasher at this time becau

drive up procedure may damage lockwasher.)

Apply the locknut with chamfered face toward the beari

after lubricating the face of the locknut next to the bearin

Hand tighten the nut with a spanner wrench until the adaptersleeve can neither be moved axially nor rotated on the sh

Then with a hammer drive the spanner wrench until the loc

nut has been turned 90 or turn on the adapter slee

CAUTION: A loose adapter sleeve can lead to the inner r

turning on the adapter sleeve and/or the adapter sleeve turn-

ing on the shaft. To insure that the nut is not excessively tig

make certain the outer ring of the bearing rotates free

When mounting a normal fit bearing, swiveling the outer ri

will result in a slight drag If the bearing is a C3 fit, the ou

ring will swivel freely.

Before mounting spherical roller bearings on adopters, t

internal cleoronce should be checked and recorded Meas

the unmounted internal clearance in the bearing by inserti

progressively larger feeler blades the full length of the ro

between the most vertical unloaded roller and the outer r

sphere Do not roll the feeler blade through the clearan

slide it through Record the measurement of the largest s

blade that will slide through. This is the unmounted inter

clearance. The bearing should be resting upright on a tab

when making this check


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Adapter Mounting

After mounting the bearing on the shaft and adapter

sleeve, the locknut is tightened suficiently to reducethe initial c learance by the required amount. This is

checked in the same manner as above, by using the

feeler gauge. The decrease in internal clearance after

mounting c an be found in SKF Engineering Data

Catalog 140-l 10.

TEMPERATURE CONDITIONS

Certain types of bearing applications require the

consideration of variable temperature conditions.

For Example: An induced draft fan handling gases at

high temperature. The fan wheel is mounted on the

shaft. Therefore, thatport of the shaft in the fan casingis subjected to the high temperatures. The bearings are

usually mounted directly outside the fon casing. Thus,

the temperature of the shaft at the bearing location is

considerably higher than the room temperature. It

follows that the inner ring of the bearing (mounted on

the shaft) will be considerably hotter than the outer

ring. This is true, as the outer ring is mounted in the

housing which is isolated from the fan and not sub-jetted to the high temperoture. As a result, the innerring will expand more than the outer ring. This action

CLEARANCES TOPERMIT AXIAL MOTION

reduces the internal clearance in the bearing-in addi-

tion to the reduction due to the tight fit on the shaft.

To compensate for this additional reduction of internal

clearance in the bearing, some provision must be made.

Bearings with an internol clearance grearer thanstandard should be used. This additional clearance

will compensate for internal clearance reduction due

to the temperoture differential between the inner and

outer rings. There are other cases where bearings with

internal clearance greater than standard are required.

Among these are dryer cylinder bearings in paper

mac hinery where steam passes through the hollow

shaft - shaker screens where tight housing fits arerequired - high speed applications where the tem-perature rise in the bearing, due to speed and load,

is abnormal - etc.It is desirable that such cases, and applications where

extremely high temperatures are involved, be referred

to the SKF Applications Engineering Department.

If this additional internal c learance is not provided,

the bearing will be excessively tight internally and

cannot operate successfully. Excessive high operating

temperotures and subsequent break-down of the

lubricant due to carbonization will occur.

FREE AND HELD BEARINGS

A temperoture variation will expand or contrac t the

component parts of any machine. Due to this condition,

it is essential that such parts be permitted to expond

or contract without restriction. For that reason, only one

bearing on any one shaft should be fixed axially in the

housing (called a held bearing) to prevent axial

or end motion.

STABILIZING RING TOLOCATE BEARING AXIALLY

MOUNT IT ON LOCKNUT SIDE

Free Bearing

12

Held Bearing


15/42

All other beorings on that same shaft should have

adequate axial clearance in the housing (referred to

as free bearings). Such free bearings will permit the

shaft to elongate and contract without restriction.

In gear reducers where herringbone gears are used,

only one bearing on one of the shafts should be held,

usually the input shaft. It is evident that the V shape

of the gear teeth will locate the other shaft axially.

When a flexible coupling is used to connect two shafts,

a held bearing is required on each of the shafts-

as a flexible coupling permits end motion of both shafts.

LUBRICATION

The bearing unit can usually be lubricated with a good

grade of lithium base grease for normal loads, speedsand operating conditions. The bearing housing shouldbe filled approximately one-third full with grease.

An excessive quantity of grease will build up in-

ternal pressure in the bearing housing and result in

high temperatures-and subsequent damage to the

bearing.

Here is a safety measure to combat this danger when

adding lubricant to the bearing. After the lubricant

added, remove the plug (preferably at the lower ho

of the housing) while the bearing is in operation. Th

permits the excessive lubricant to flow out of thhousing and relieve the internal pressure. When t

flow of grease ceases, be sure to replace the plug.

Speed and other operating conditions, in some caserequire that oil lubrication be used. In that event, t

bearing housing should be equipped with adequa

oil fittings. Such fittings should provide a static oil lev

at the center of the lowest ball or roller in the bearin

It is preferable to use sight glass oil gauges whic

can be clearly marked for static and operating leve

The operating level is slightly lower than the stat

level due to agitation of the oil.

The static level can be marked on the gauge befo

the unit is assembled. The operating level c an b

determined only after the bearing is in operation. Tgauge should also be marked for the operating lev

and the lubricant, at no time, should be permitted

drop below this point. But, never restore the oil levto the static marks while the bearing is running.

The subject of lubrication is discussed in greater de

in another public ation, A G UIDE TO BETTER BEARIN

LUBRICATION, 144-l 10.

1


16/42

DOS AND DONTS FOR BEARINGS.s. assembly, maintenance, inspection and lubrication

Do work as close to the ideal conditions pictured here.

Dividends in bearing performance will result.

Dont work under the handic ap of poor tools, rough

bench, plenty of dirt.

DO work with clean tools, in clean surroundings.

DO remove all outside dirt from housing before

exposing bearings.

DO handle with clean, dry hands.-DO treat a used bearing as carefully as a new one.

DO use clean solvents and flushing oils.

DO lay bearings out on clean paper.

DO protec t disassembled bearings from dirt and

moisture.

DO use clean, lint-free rags if bearings are wiped.

DO keep bearings wrapped in oil-proof paper when

not in use.

DO clean inside of housing before replacing bearings.

DO install new bearings as removed from packages,

without washing.

DO keep bearing lubricants clean when applying and

cover containers when not in use.

14

DONT work in dirty surroundings.

DONT use wooden mallets or work on rough or dirty

bench tops.

DONT use dirty, brittle or chipped tools.

DONT handle bearings with dirty, moist hands.

DONT spin uncleaned bearings.

DONT spin any bearings with compressed air.

DONT use same container for cleaning and final

rinsing of bearings.

DONT use c otton waste or dirty cloths to wipe

bearings.

DONT expose bearings to moisture or dirt at any

time.

DONT scratch or nick bearing surfaces.

DONT remove grease or oil from new bearings.

DONT use incorrect kind or amount of lubricant.


17/42

Proper core begins in the

stock room. Store bearings in

originol unopened packages,

in o dry place. The bearing

number isplainly shown on the

wrapping. Before packaging,

the manufacturer protected

the bearing with a grease

coating. An unopened pock-age means continued protec-

tion. Do not open carton until

reody to use.

Open package only when

ready to install bearing. Hon-die bearing with clean, dryhands and with clean rags.

Lay bearing on clean paper

and keep covered. Never ex-

pose bearing on a dirty bench

or floor. Never use o beoring

as o gauge lo check eitherthe housing bore or the shaftfir.

Dont wash o new bearing-it is already clean and the

slushing oil should not be

removed. Old grease can be

washed from a used bearing

with a solvent but fluid and

container must be clean.

After this cleaning, wash thebearing out thoroughly with

light oil and then relubricate.

Bearings should be washed

only when necessary.

Before mounting, be sure shaft

size is within the specified

tolerances recommended for

the bearing. The bearing seat

should be perfectly round and

not tapered. It should be c lean

and free from nicks ond burrs.

Shaft shown is too worn loproperly seat bearing-dont

use it. Support shaft firmly ina clean place-if in a vise,

protect it from vise jaws. Pro-

tectors can be soft metal,

wood, cardboard or paper.

Note: To shrink a sealed bearing an a

shaft, use only method 2, and limit tem-

perature to 107C (225F).

To press becring oh s

clean piece of tubing

shaft and rest it an in

Befare pressure is apbearing, apply a coa

oil or micronized graph

bearing seat and th

bare This will facilitate

bly Be sure bearing

an shaft, then apply prtapping end of pipe w

mer or using arbor pre

to illustration (A) an p

To shrink an open bea

shaft, expand bearing

1. Boiling in emulsion of 10soluble oil in water for 15 to

utes .Be sure to place suppbearing to isolate itcontainer as contact will obearing

2 Heat in a clean tempera

trolled electric oven or on

to a maximum of121C12about fifteen minutes bearing but do notoverheprevent seizing onthe colbearlngisinplaceagainstder. lock it immediatelv wnutOtherwise, in shrinkingmaymoveaway fromitsptionagainstshaftshoulder

When mounting in

housing, check bore

ing to see that it is

specified tolerances

perfectly round. Bear

not be pinched by sm

or because of a cocke

ring. Dont switch hous

-they are not inter

able. An undersized

bore or on out-of-rou

will pinch the bear

cause early failure.

Some precaution mus

ercised when mounti

ing in a solid housing;

outer ring should be

square with the hous

before any pressure

plied. Here again, thebore should be wi

specified tolerances

bearing size and sh

perfectly round. The

bore and bearing

diameter should be

with light oil or mi

graphite to facilitate ass


18/42

Cover the unfinished job when

left for only a few hours or

until the next day. Rewrap

each bearing to keep out dirt

and moisture. When this &necessary, use grease-proof

paper. lf you do not take care

of bearings during installation,they will not lost long.

Type of lubricant usually de-

pends on operating conditions

-follow machine builders in-

structions. When oil is used,

cover about half of bottom

ball or roller. It is preferred

that o sight oil gauge be used

and marked so as to show

static and operating oil levels.

This will greatly help to deter-mine when additional oil is

required. The operating level

is different than the static level

and can be determined only

when the bearing is in oper-

ation.

Be sure bearing is square with

and held fhmly against shaft

shoulder. Secure it with a

locknut and loc kwasher.

Housing covers must be tight

to keep lubricant in and dirt

wt. After heid beoring has

been positioned, the free

bearing should be located

centrally in its housing to

permit expansion and can-

traction of the shaft.

16

To remove o bearing from the

shaft, force inner ring with

press or draw bar and plate.

Shaft shoulder must be smaller

than inner ring to make such

removal. A variety of beoringpullers are ovailable. The use

of such speciaiized tools will

more than pay for themselves

by preventing damage to

serviceable bearings. Refer

to group of illustrations (8)

at right.

(A)An arbor press is equally

good for either mounting

or removing beorings.

Bearing pullers

which may be used sep-

To drive shoft 2of beoring, use a

soft metal slug

which will not mar

the shaft.

arately or in various com-

binations to pull or push

complete beorings or

individual rings.

(C lNever pound di-

rectly on o bearing

or ring. It will

likely damage both

shoft and bearing.


19/42

Do not spin be ar ings before clea n ingDirt ca n c ause ser ious scra tc h ing.

i

Soak bea r ings thoroughly in p lenty of so lvent

INSPECTION and ASSEMBLY \REQUIRE CLEAN BEARINGS

Dont try to judge the condition of a beoring until after

it has been cleaned.

Dont spin dirty bearings. Rotate them slowly while

washing.

Dont spin ony bearings with an air hose. Rotote one

ring by hond when using air to expose all parts of

bearing.

Bearings with a shield or seal on one side only should

be washed, inspected ond handled in the same manner

as bearings without shields or seals.

Bearings with shields or seals on both sides should not

be woshed. Wipe them off to keep dirt from working

inside. Smooth turning bearings can be c oated with

protective lubricant, then wrapped and stored or usedin their original application.

If a small tank and wire baskets for soaking and

washing bearings are not available, a clean grease

can or bucket filled with solvent can be used. Let the

bearings soak long enough to loosen the grease and

dirt. Thot may toke several hours or longer. Then slosh

the bearing around near the top of the container,

giving it a turn now and then until it is clean. Rinse in aclean container of clean solvent.

Bearing cleaning solutions are generally petroleum sol-

vents intended for bearing cleaning and are preferred.

Rinse them in clea n so lvent , ligh t o i l or kerosene. Do n o tspin by force o f a i r . Holdboth rings.Use c lean, drya ir.

17


20/42

All solvents are highly inflammable and precautions

should be taken to prevent fires.

A short, clean bristle brush from which the bristles will

not come out or break off is helpful in removing dirt,

scale or chips.

After the bearings hove been thoroughly c leaned,

inspect them immediately.

Inspected bearings which are considered good enough

to use again, but cant be reossembled in the equip-

ment on the same doy, should be dipped in slushing

compound arid stored overnight in a tightly coveredpan.

If inspec ted bearings are to be stored for more than

a few days, dip them in a protective lubricant or coat

all surfaces with a light grease, rototing them to work

the grease thoroughly around the rolling members and

on the raceways. Wrap the beorings in greaseproof

paper and place in o clean box or carton. Where

cartons ore not obtoinoble, wrap them in o waterproof

paper and mark the outside of the pockage to identifythe bearing. - -DO not leave bearings exposed in portial assemblies.

Cover the bearings until ready to c omplete the

assembly, to prevent damage by moisture, dirt or

other foreign matter. Any clean cloth or paper will do ,

as long OS the bearings are well covered. I

DOS ad DONTS on LUBRICATIONFollow instructions when furnished with machinery. Use

only grease where grease is specified and oil where

oil is spec ified. Be sure to use exac tly the kind of

lubricant the instructions specify.

Store grease in clean containers. Handle grease with

clean paddles or grease guns. Keep grease con-

tainers covered.

Dont overfill. Grease or oil will purge out of overfilled

housings past seals and closures, collect dirt and cause

trouble. Too much lubricant will also cause overheating.

This is particularly true of bearings running at high

speeds where the churning of the lubricant will causethe bearings to run excessively hot.

Dont permit any machine to stand around for months

without turning it over once in a while so that all

surfaces of the bearings will be covered with lubricant.

Oil tends to drain down off a standing bearing and

moisture may condense in the housing and c ause

corrosion.

Inspect seals and vents regularly.

Bearings porfiolly o s se m b l d willcollect harmfu l dust or dirtif left standing too long.

Cover wi th c / eon clo th o r- p a p e r,especially i f assem bly w il l not

be completed for several hoursor until nex tdoy

18


21/42

TROUBLESHOOTING

This sec tion presents some helpful hints on bearing troubleshooting-what to look for when a customer

complains, how to recognize the reason for the trouble and practical solutions, wherever possible.

Complaints of bearing trouble c an be reduced to a few c lassifications-listed in the following order. For

ease of relating them to conditions and solutions, they are coded A to G inclusive.

CUSTOMERS

COMPLAINT

A - Overheated bearing

B-- Noisy bearingC - Replacements are too frequentD - Vibration

E - Unsatisfactory performance of equipment

F - Bearing is loose on shaft

G-

Hard turning shaft

The following table lists some typical conditions that will result in bearing failures.

The first column numerically c odes eac h typic al c ondition (Nos. 1 to 54 inclusive).

The third column is the customer-complaint code (A to G) to which the condition

may apply.

TYPICAL CONDlTlONS RESULTING IN BEARING FAILURESEACH CONDITION COULD CAUSE -ANY ONE OF THE COMPLAINTS LISTED OPPOSITE THE RESPECTIVE CONDITION IN COLUMN 3

CODE CONDITION COMPLAINT

1. lnadequote lubrication (Wrong type of grease or oil). . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Insufficient lubrication (Low oil level - l o s s of lubricant through seals). . . . . . . . . . . . . . I-A-5-C-GA-B-C-G3 . Excessive lubrication (Housing oil level too high or housing packed with grease). . . . . . . . A-G

4. Insufficient clearance in bearing (Selection of wrong fit). . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-E-G

5. Foreign matter acting as on abrasive (Sand, carbon, etc.). . . . . . . . . . . . . . . . . . . . . . . . B-C-D-E-G

6 . Foreign matter acting as a corrosive (Water, acids, paints, etc.). . . . . . . . . . . . . . . . . . B-C-D-E-G

7. Bearings pinched in the housing (Bore out of round). . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-D-E-G

8. Bearings pinched in the housing (Housing warped). . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-D-E-G

9. Uneven shimming of housing base (Distorted housing bore - possible cracking of base). . A-B-C-D-E-G10. Chips in bearing housing (Chips or dirt left in housing]. . . . . . . . . . . . . . . . . . . . . . . . . . B-C-D-E-G

11. High air velocity over bearings (Oil leakage). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C

12. Seals too tight (Cup seals). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-G

19


22/42

TYPICAL CONDITIONS RESULTING IN BEARING FAILURES (Continued)

CODE CONDlTlON COMPLAINT

13. Seals misaligned (Rubbing against stationary parts). . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-G

14. Oil return holes plugged (Oil leakage). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A

15. Preloaded bearings (Opposed mounting). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-G

16. Preloaded bearings (Two held bearings on one shaft). . . . . . . . . . . . . . . . . . . . . . . . A-B-C-E-G

17. Bearing loose on shaft (Shaft diameter too small). . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-C-D-E-F

18. Bearing loose on shaft (Adapter not tightened sufficiently). . . . . . . . . . . . . . . . . . . . . . . B-C-D-E-F

19. Bearing too tight internally (Adapter tightened excessively), . . . . . . . . . . . . . . . . . . . . . A-E-C-E-G

20. Split pillow block with uneven surfaces (Oil leakage). . . . . . . . . . . . . . . . . . . . . . . . . . . C

21. Spinning of outer ring in housing (Unbalanced load). . . . . . . . . . . . . . . . . . . . . . . . . . . A-C-D-E

22. Noisy bearing (Flat on roller or ball due to skidding). . . . . . . . . . . . . . . . . . . . . . . . . . . B-D-E

23. Excessive shaft expansion (Resulting in opposed mounting). . . . . . . . . . . . . . . . . . . . . . . A-B-C-E-G

24. Excessive shaft expansion (Resulting in insufficient clearance in bearing). . . . . . . . . . . . . A-C-E-G

25. Tapered shaft seat (Concentration of load in bearing). . . . . . . . . . . . . . . . . . . . . . . . . . C-D-E

26. Tapered housing bore (Concentration of load in bearing). . . . . . . . . . . . . . . . . . . . . . . C-D-E

27. Shaft shoulder too small (Inadequate shoulder support-bending of shaft) . . . . . . . . . . . C-D-E-G

28. Shaft shoulder too large (Rubbing against bearing seals). . . . . . . . . . . . . . . . . . . . . . . . A-B-C

29. Housing shoulder too small (Inadequate shoulder support). . . . . . . . . . . . . . . . . . . . . . . C-D-E-G

30. Housing shoulder too large (Distortion of bearing seals). . . . . . . . . . . . . . . . . . . . . . . . B-C-G

31. Shaft fillet too large (Bending of shaft) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-D-E-G

32. Housing fillet too large (Inadequate support). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-D-E-G

33. Insufficient clearance in labyrinth seals (Rubbing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-G

34. Oil gauge breather hole clogged (Shows incorrect oil level). . . . . . . . . . . . . . . . . . . . . . A-C

35. Shafts out of line (Linear misalignment). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-C-D-E-G

36. Shafts out of line (Angular misalignment). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-C-D-E-G

37. Constant oil level cups (Incorrect level). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-C38. Constant oil level cups (Located against rotation of bearing]. . . . . . . . . . . . . . . . . . . . A-C

39. Lockwasher prongs bent (Rubbing against bearing). . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-E-G

40. Incorrect positioning of fingers (Rubbing against covers). . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-G

41. Pedestal surface uneven (Bending of housing causing pinching of bearing). . . . . . . . . . . A-C-D-E-G

42. Ball or roller denting (Hammer blows on bearing). . . . . . . . . . . . . . . . . . . . . . . . B-C-D-E

43. Noisy bearing (Extraneous conditions). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B

44. Lubricant leakage and entrance of dirt into bearing (Worn out seals). . . . . . . . . . . . . C

45. Vibration (Excessive clearance in bearing). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-E

46. Vibration (Unbalanced loading). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-E

47. Hard turning shaft (Shaft and housing shoulders out of square with bearing seat). . . . . . . C-E-G

48. Bearing loose on shaft (Knurling and center punching of shaft for bearing seat). . . . . . . A-F

49. Discoloration of bearings (Use of blow torch to remove bearing). . . . . . . . . . . . . . . . . . a

50. Oversized shaft (Overheating and noise). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-E-G

51. Undersized housing bore (Overheating of bearing). . . . . . . . . . . . . . . . . . . . . . . . . . . . A-B-C-E-G

52. Oversized housing bore (Overheating of bearing-spinning of outer ring). . . . . . . . . . A-B-C-D-E

53. Enlarged housing bore (Excessive peening of non-ferrous housings). . . . . . . . . . . . . . . A-B-C-D-E

54. Noisy bearing (False brinelling). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B

20


23/42


24/42

The following pages offer PRACTICAL SOLUTIONS to the TROUBLE CONDITIONS which originated .your ~customers complaint.Colum n 1 refers back to the code of the typical condition listed in the foregoing table.Column 2 is the reason for that condition -ond column 3 is your pracficol solution .

TROUBLE CONDITIONS AND THEIR SOLUTIONOVERHEATED BEARING

Complaint AREAS6N FOR CONDITION PRACTICAL SOLUTION

Wrong type of grease or oil caus-ing break-down of lubricant.

Insufficient grease in housing.

Purge bearing until only lower halfof housing is rh to sh full of grease.Using oil lubrication, reduce level to

quate intern al clearance for con-ditions where external heat is Replacement bearing should have identical marking as originalconducted thru shaft, thereby bearing for proper internal clearance. Check with SKF if bearing

ng excessively the in- markings have become ind istinct.

Housing bore out of round. Check and scrape housing bore torelieve pinching of bearing. Besure pedesta l surface is Rat, andshims cover entire area of pillo w

Leather or composition seals Replace leather or compositionwith excessive spring tension or seals with ones having reduced

spring tension. Lubricate seals.

Rotatinq seals rubbing against Check running clearance of rotat-ing seal to eliminate rubbing.Correct alignment.

21


25/42

OVERHE ATED BEARING - Complain t A (Continued)

Clean holes. Drain out used oil-refil l ing to proper oil level withfresh lubricant.

Opposed mounting.insert gasket between housing andcover flang e to relieve axial pre-loading of bearing.

Back off covers in one of the hous-ings, using shims to obtain ade-quate clearance of outer ring, topermit free axial bearing motion.

Loosen locknut and sleeve assem-bly. Retighten sufftciently to clampsleeve on shaft but be sure bear-ing turns freely.

ing with one having proper bore.

incorrect oil level. Result: no lu- Clean out clogged hole to vent oilbricant in bearing.

LINEAR MISALIGNMENT

ANGULAR MISALIGNMENT


26/42

OVERHEATED BEARING - Complaint A (Conr inuad)DE TOPICA1 REASON FOR CONDITION PRACTICAL SOLUTIONIDITION

incorrect mountin g of constant The oil level at standstill must notoil level cup. (Too high or too exceed the center of the lowermostlow.) Cup located opposite rota- ball or roller. Locate cup with rota-

-38 tion of bearing permitting ex- tion of bearing. Sketch illustratescessive flow of oil, resulting in correct position of constant leveltoo high oi l level. oil cup with respect to rotation.

Better replace constant level oiler -i I IIATIC 01~ L*YGL* WC1).TWC OIL LVCL

, wawnG.

($Lm

r39 Prong rubbing against be aring. Remove lockwasher - straightenprong or replace with new wosher. \ -

1

-71 d

-L-!-i- --Y

Knurling and center punching of Unsafisfactory because high spots are flattened when load is applied ,48 bearing seat on shaft. when fit is loose, metallire shaft and regrind to proper size.

Bearing seat diameter machinedoversize, causin g excessive ex-

50 pansion of bearing inner ring, Grind shaft to get proper fit between inner ring of bearing and shaft.thus reducing clearance in bear-ing.Pounding-out of housing bore

53 due to soft metal. Result: en- Rebore housing and press steel bushing in bore. Machine bore oflarged bore . . . causing spin- bushing to correct size.ningyf outer ring in housing.

NOISY BEARINGComplaint BWrong type of grease or oil Consult reliable lubricant manufacturer for proper type of lubricant.i causing break-down of lubri- Check SKF Catalog instructions to determine if oil or grease shouldcant. be used.Low oil level. Loss of lubricant Oil level should be at center of lowest bail or roller in bearing, at2 through seal. standstill. IInsufficient grease in housing. Using grease, lower half of pillow block should be /2 to $+ full.See Illzrsfration-CornpIrii l lt A, Condition .?Bearings selected with inade-quate internal clearance for con-

4 ditions whe re external heat is Replaceme nt bearing should have identical marking as original bear-conducted through shaft, thereby ing for proper internal clearance. Check with SKF if markings havebecome indistinct.expanding excessively the innerring.Foreign matter (dirt, sand, car-5 bon, etc.) entering bearing Cleon out bearing housing. Replace worn-out seals or improve sealhousing. design to obtain adequa te protection of bearing.

Corrosive agents (water, acids,6 paints, etc.) entering the bear- Additio n of a shroud and (or) finger to throw off foreign matter.ing housing.

7-8 Housing bore out of round. Check and scrape housing bore to relieve p inching of beoring. Be9-51 Housing warped. Excessive dis- sure pedestal surface is flat, ond shims cover entire area of pillowtortion of housing. Undersized block base.housing bore. See Ifl l lstratiofi-Conlplrri l lt A. Coudibo ns 7-8-g-41-51


27/42

NOISY BEAIWG - Complainr 8 (Continued)DDE TOYPICAL REASON FOR CONDITIONNDITION PRACTICAL SOLUTION

Failure to remove chips, dirt,10 etc. from bearing housing be- Carefully clean housing, and use fresh lubricant.

fore assembling bearing unit.

13 Check running clearance of rotating seal to eliminate rubbing.Rotating seals rubbing against Correct alignment3-40 stationary parts. ee Il iustrdtion -Comp laint A, Condition 13-33-40

15Insert gasket between housing and cover flange to relieve axial

Opposed mounting. pre-loading of bearing.See Il lustration-Comp laint A, Condition 1 i

6-23 Two held bearings on oneBack off covers in one of the housings using shims to obtain ade-

shaft. Ex cessive shaft expan sion. quote clearance of outer ring to permit free axial bearing motion.See Il lz,stratjon-Co rnplJj,II A, Conditions I G-23-24

Metallize shaft and regrind to ob- ~ .\ \.Shaft diameter too small. rain proper fit LOOSE7-18 Adapter not tightened sufi- Retighten adapter to get firm grip

ciently. on shaft.I - A

,\~\, :,. , r;-- -19 Adapter tightened excessively. Loosen locknut and sleeve assembly. Retighten sufficiently to clampsleeve on shaft but be sure bearing turns freely.See Il lz~stratjon-Comp l~jnt rA, Condition 19

22 Flat on ball or roller due to Carefully examine bails or rollers, looking for flat spots on theskidding. (Result of fast starting.1 surface. Replace bearing.

28 Rbbbing of shaft shoulder Remachine shaft shoulder to clear seal.against bearing seals. See Ilhtration-Comp laint A, Condition 28--

30 Distortion of bearing seals. Remachine housing shoulder toclear seal.

39 Prong rubbing against bearing. Remove lockwasher-straighten prong or replace with new washer.See Il lustration-Comp laint A, Condition 39

42 incorrect method of mounting. Replace with new bearing. Dont hammer any part of bearingHammer blows on bearing. when mounting.

43 Interference of other movable Carefully check every movin g part for interference. Reset parts toparts of mach ine. provide necessary clearance.

Distorted shaft and other parts Only in extreme cases sh ould a torch be used to faCihte removal49 of bearing assembly. of a failed bearing. Care should be exercised to avoid high heatconcentration at any one point so distortion is eliminated .

24


28/42

ODE TOYPICALlNDlTlON

NOISY BEARIN G - Com plaint 5 (Continued)

REASON FOR CONDITION PRACTICAL SOLUIION

Bearing sear diameter machinedoversize causin g excessive ex-

50 pansian of bearing inner ring, Grind shaft to get proper fit between inner ring of bearingthus reducing clearance in and shaft.bearing.

Unbalanced load. Housing bore Rebalance unit. Replace housing with one having proper bore.

Pounding-out of housing boredue to soft metal. Result: en- Rebore housing and press steel bushing in bore. Machine bore oflarged bore . . . causing spin- bushing to correct size. If loads are not excessive, tighter fit in hous-

ning of outer ring in housing. ing, without the use of the steel bushing, may correct the trouble.

54 Bearing exposed to vibration Carefully examine bearing for wear spots separated by distancewhi le machine is idle. equal to the spacing of the balls. Replace bearing.

REPLACEMENTS ARE TOO FREQUENTComplaint c

1 wrong type of grease or oil Consult reliable lubricant manufacturer for proper type of lubricant.causing break-down of lubricant. Check SKF Catalog instructions to determine if oil or grease shouldbe used.- -

Low oil level. Loss of lubricant Oil level should be at center of lowest ball or roller in bearing.2 through seal.

Insufficient grease in housing. Using grease, lower half of pillow block should be /2 to $$ full.See Illzi~t~ation-Complaint A, Condition 2Bearings selected with inade-quate internal clearance for con-

4 ditions where external heat is Replacemen t bearing should have identical marking as originalconducted thru shaf+, thereby bearing for proper internal clearance. Check with SKF if bearingexpanding excessively the in- markings have become indistinct.ner ring.

Foreign matter (dirt, sand, car-5 bon, etc.) entering into bearing Clean out bearing housing. Replace worn-out seals or improve

housing. seal design to obtain adequate protection of bearing.

Corrosive agents (water, acids,6 paints, etc.) entering the beor- Additio n of a shroud and Ior) flinger to throw ofF the foreign matter.

ing housing.

Housing bore ou t of round. Check and scrape housing bore to relieve pinching of bearing.7-8-9 Housing warped. Excessive dis- Be sure pedestal surface is flat, and shims cover entire area of11-51 tortion of housing. Undersized pillow block base.

housing bore. See Ihtration-Com plaiaint A, Conditions 7-8-9-4 I-5 IFailure to remove chips, dirt,

10 etc. from bearing housing be. Carefully clean housing, and use fresh lubricant.fore assembling bearing un it.

25


29/42

CODE 10TYPICALONDITION

REPLACEM ENTS ARE TOO FREQUENT - C~mplo in t C (Cont inued)

REASON FOR CONDITION PRACTICAL SOLUTION

Oil leakage resulting from air11 flow over bearings. (Example:forced draft fan with air inlet Provide proper baffles to. divert direction of air flow.

over bearings.)

15 Opposed mounting. Insert gasket between housing and cover flange to relieve axialpre-loading of bearing.See Illustration-Comp laint A, Condition IS

16 Two held bearings on one Back of f covers in one of the housings, using shims to obtain ade-23-24 shaft. Excessive shaft expansion. quote clearance of outer ring, to permit free axial b earing motion.See Illustration-Comp laint A, Conditions 16-23-24

17 ,* Shaft diameter too small.s Metallize shaft and regrind to obtain proper fit.Adapter insufficiently tightened. Retighten adapter to get firm grip on shaft.See Illustration-Comp laint B, Conditions I 7- I 8

19 Adapter tightened excessively. Loosen locknut and sleeve assembly. Retighten sufficiently to clampsleeve on shaft but be sure bearing turns freely.See Illustration-Comp laint A, Condition 19UCVLHMFACES

If not severe, use thin layer of --l20 Oil leakage at housing split.Jxcessive loss of lubrica nt. gasket cemen t. Dont use shims.Replace housing if necessary.L!I!QLOR @ /

.ORI Ps i; P

21-52 Unbalanced lood. l-lousing bore Rebalance machine. Replace housing with one having proper bore.too large. See Illustration-Comp laint A, Con ditions 2 I -52

Unequa l load distribution an Rework shaft, housing, or both, to25 26s bearing. obtain proper fit. May requirenew shaft and housing.

27 Inadequate shoulder support Remachine shaft fillet to relievecausing bendin g of shaft. stress. May require shoulder collar.

J29 Inadequate support in housing Remachine housing fillet to relievecausing cocking of outer ring. stress. May require shoulder collar.

28 Rubbing of shaft shoulder Remachine shaft shoulder to clear seal.against bearing seals. See Illustration-Comp laint A, Condition 28

30 Distortion of bearing seals. Remachine housing shoulder to clear seal.See Illustration-Comp laint B, Condition 30

26


30/42

REPL ACEM ENTS ARE TOO FREQUEN T - CornplaIn, C (Continued)

Remach ine shaft f i l let to obtainneven expansion 0

Distort ion of housin

stationary parts.

sing f i l let to obtain

earance of rotat ing seal to el imina te rubbing.

The oi l level at standsti l l must not exceed the center of the lowermostball or rol ler . Locate cup with rotat ion of bear ing. Replace constantlevel oi ler with sight gage.

Incorrect method of mountiHamme r blows on bear ing. when mountin

Excessively worn leathe r (or Replace seals after thoroughly44 composit ion), or labyr inth seals.

Result : lubr icant loss; dir t get-t ing in to bear ing. fresh lubr icant.

47Shaft and housing shoulders andface of locknut out-of-square Remach ine parts to obtain squareness.with bear ing seat.

50Bearing seat diameter machinedoversize, caus ing excessive ex- Grind shaft to get proper f i t between inner r ing of bear ingpansion of bear ing inner r ing, and shaft.thus reducing clearance inbear ing.

53Pounding-out of housing boredue to soft metal. Result : en- Rebore housing and press steel bushing in bore. Machine bore oflarged bore . . . causing spin- bushing to correct size.ning of outer r ing in housing.

VIBRATIONComplaint D

Foreign matter [dir t , sand, car-5 bon, etc.) enter ing bear ing Clean out bear ing housing. Replace worn-out seals or improve seal

housing. design to obtain ad equate protect ion of bear ing.

27


31/42

VIBRATION - Comp lafnf W (Continued)

REASON FOR CONDITION PRACTICAL SOLUTION

Corrosive agents (water, acids,6 points, etc.) entering the bear- Addition of a shroud and (or) flinger to throw off foreign matter.

ing housing.

Housing bore out of round. Check and scrape housing bore to relieve pinc hing of bearing.7-8 Housing warped. Excessive dis- Be sure pedestal surface is flat, and shims cover entire area of9-41 tortion of housing. Undersized pillow block base.

housing bore. See Ihtration-Corn/hint A, Conditions 7-8-P-41 -SIFailure to remove chips, dirt,

10 etc. from bearing housing be- Carefully clean housing, and use fresh lubricant.fore assembling bearing unit.

Shaft diometer too small. Metallize shaft and regrind to obtain proper fit.17-l 8 Adapter not tightened sufi- Retighten adapter to get firm grip on shaft.

ciently. See Ihtration-Com plaint B, Conditions 17-l 821-52 Unbalanced load. Housing bore Rebalance machine. Replace hous ing with one having proper bore.

too large. See Ibstration-Com plaint A, Conditions 21-5222 Flat on ball or roller due to Carefully examine balls or rollers, looking for fiat spots on theskidding. (Result of fast starting.9 surface. Replace bearing,

25-26 Unequa l load distribution on Rework shaft, hous ing, or both, to obtain proper fit. May requirebearing. new shaft and housing.See Illustration-Complaint C, Conditions 25-26

27 __ Inadequate shoulder support Remachine shaft fillet to relieve stress. May require shoulder collar.causirig bending of shaft. See Illustration-Compiaint C, Condition 27

29Remachine housing fillet to relieve stress. May require shoulderInadequate support in housing collar

causing cocking of outer ring. See il iustration-Complaint C, Condition 29Distortion of shaft and inner31 ring. Uneven expansion of bear- Remachine shaft fillet to obtain proper support.ing inner ring. See Mustration -Comp laint C, Condition 3 I

32 Distortion of housing and outer Remachine housing fillet to obtain proper support.ring. Pinching of bearing. See Ihstration-Com plaint C, Condition 32Incorrect linear or angular align- Correct alignme nt by shimming pillow blocks. Be sure shafts are

35-36 ment of two or more coupled coupled in straight line--especially when three or more bearingsshafts with two or more bearings. operate on one shaft.See Ihstration-Com plaint A, Conditions 35-36

42 Incorrect method of mounting. Replace with new bearing. Dont hammer any part of bearingHammer blows on bearing. when mounting.

45 Excessive clearance in bearing,resulting in vibration. Use bearings with recommended internal clearances.

46 Vibration of machine. Check balance of rotating ports. Rebalance machine.

Pounding-out of housing bore53

Rebore housing and press steel bushing in bore. Machine bore ofdu e t0 Soft metal. Result: en- bushing to correct sizelarged bore . . . causing spin-ning of outer ring in housing.

28


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UNSATISFACTORY PERFORMANCE OF EQUIPMENTComplaint I?

%X? REASON FOR CONDITION:ONDIllON PRACTICAL SOLUTIONBearings selected with inade-quate interna l clearance for con-ditions where external heat is Replacement bearing should have identical marking as original4 conducted thru shaft, thereby beoring for proper internal clearance. Check with SKF if bearingexpandi ng excessively the in- markings have become indistinct.ner ring.

Foreign matter (dirt, sand, car-5 bon, etc.) entering bearing Clean out bearing housing. Replace worn-out seals or improvehousing. seal design to obtain adequate protection of bearing.

Corrosive agents (water, acids,6 paints, etc.) entering the bear- Addition of a shroud and (or) flinger to throw off foreign matter.

ing housing.

Housing bore out of round. Check an d scrape housing bore to relieve pinchin g of bearing .7-8-9 Housing warped. Excessive dis- Be sure pedestal surface is flat, and shims cover entire area of

41-51 tortion of housing. Undersized pillow block base.housing bore. See I l lustration-complaint A, Condit ions 7-8-g-41-51Failure to remove chips, dirt,10 etc. from bearing housing be- Carefully clean housing, and use fresh lubricant.fore assembling bearing unit.

-16 Two held bearings on one Back off covers in one of the housings,usin g shims to obtain ade-

23-24 shaft. Excessive shaft expansion. quate clearance of outer ring, to permit free axial bearing motion.See Ihstration-Complaint A, Condit ions 16-23-24Shaft diameter too small. Metallize shaft and regrind to obtain proper fit.

17-18 Adapter not tightened sufTi- Retighten adapter to get firm grip on shaft.ciently. See I l lustration-Complaint B Condit ions 17-i 8Loosen locknut and sleeve assembly. Retigh ten sufficiently to clamp19 Adapter tightened excessively. sleeve on shaft but be sure bearing turns freely.See Illustration-Com plaint A, Cordition 19

21-52 Unbalanced load. Housing bore Rebalance machine. Replace housing with one having proper bore.too large. See I l lustration-Complaint A, Condit ions 21-52

22 Flat on ball or roller due to Carefully examine balls or rollers, looking or flat spots on theskidding. (Result of fast starting.) surface. Replace bearing. #

Unequal load distribution on Rework shaft, housing, or both, to obtain proper fit. May require25126 bearing. new shaft and housing.See I l lustration-Complaint C, Condit ions 25-26

27 Inadeq uate shoulder support ,Remac hine shaft fille t to relieve stress. May require shoulder collar.causing bending of shaft. See Ihstration- -Complaint C, Condit ion 27

29 Inadequate support in housing Remachine housing fillet to relieve stress. May require shouldercausing cocking of outer ring. collar.See Ihstration-Complaint C, Condit ion 29

29


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UNSATISFAC TORY PERFO RMAN CE OF EQUIPME NT - Comp loi~t E (Continued)

32 Distortion of outer housing and Remachine housing fillet to obtain proper support.ring. Pinching of bearing. See Iilustrafjon-Complain& C, Condition 32

Incorrect linear or angular align-35-36 ment of two or more coupled

shafts with two or more bearings.

Correct alignmen t by shimming pillow blocks. Be sure shafts arecoupled in straight line-especially when three or more bearingsoperate on one shaft.See Iffustration-Complaint A, Conditions 35-36

39 Prong rubbing against bearing.

42 Incorrect method of mounting.Hammer blows on bearing.

45 Excessive clearance in bearing,resulting in vibration.

46 Vibration of machine,

Shaft and housing shoulders,47 and face of locknut out of

square with bearing seat.

50Bearing seat diameter machinedoversize, caus ing excessive ex-pansion of bearing inner ringthus reducing clearance in bear-ing.

Pounding-aut of housing bore53 due to soft metal. Result: en-larged bore _ . . causing spin-

ning of outer ring in housing.

PRACTICAL SOLUTION

Remachine shaft fillet to obtain proper support.See Illustration-Complaint c, Condition 3 I

Remove lockwasher -straighten prong or replace with new washer.See Illustration-Complaint A, Condition 33

Replace with new bearing. Dont hammer any part of bearingwhen mounting.

Use bearings with recommended internal clearances.

Check balance of rotating parts. Rebalance machine.

Remachine ports to obtain squareness.

Grind shaft to proper fit between inner ring of bearing and shoft.

Rebore housing and press steel bushing in bore. Machine bore ofbushin g to correct size. If loads are not excessive, tighter fit in hous-ing, without the use of the steel bushing, may correct the trouble.

BEARING IS LOOSE ON SHAFTComplain! F

Shaft diameter too small.17-18 Adapter not tightened s&i-

ciently.Metallize shaft and regrind to obtain proper fit.Retighten adapter to get firm grip on shaft.See Illustration-CompIaint B, Conditions I 7-18

48 Knurling ond center punching Unsatisfactory because high spots ore flattened when load is ap-of bearing seat on shoft. plied. When fit is loose, metallize shaft and regrind to proper size.I IHARD TURNING OF SHAFT

Complaint G

Wrong type of grease or oil caus- Consult reliable lubricant manufacturer for proper type of lubricant.1 ing break-down of lubricant. Check SKF Catolog instructions to determine if oil or grease shouldbe used.


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HARD TURNING OF SHAFT - Comp tolnt 0 (Contlnuod)D D E 1 0IP ICA REASON FOR CONDITION PRACTICAL SOLUTIONUDlllON

Low oil level. Loss of lubricant Oil level should be just below center of lowest ball or roller i n2 through seal. bearing.

lnsuffrcient grease in housing. Using grease, lower half of pillow block should be /s to h full.See III~~~lr~.~lif~if--C~~t~ t~l~r~~~f A. Cou rlilj~JIl 2Housing packed with grease, or Purge bearing until only lower half of housing is t/2 to sh full ofoil lev el too high . . . causing

3 grease. Using oil lubrication, reduce level to just below center o fexcessive churning of lubricant,high operating temperature, oil 1lowest ball.leakage. ee Ill// ,t11lti/,t(-Cf,t)lplrl l111 A, Co uditiou 9

-_Bearings selected with inade-quate internal clearance for con- Replaceme nt bearing should have identical marking as original

4 ditions where external heat is bearing for proper internal clearance. Check with SKF if bearingconducted thru shaft, thereby markings have become indistinct.expanding excessively the in-ner ring.

Foreig n matter (dirt, sand, car- Clean out bearing housing. Replace worn-out se.ais or improve5 bon, etc.) entering bearinghousing. seal design to obtain odequate protection of bearing.

Corrosive agents (water, acids,6 paints, etc.) entering the bear- Additio n of a shroud and [or) flinger to throw off foreign matter.

ing housing.

7-8 Housing bore out of round. Check a nd scrape housing bore to relieve pinching of bearing.9-41 HousiLg warped. Excessive dis- Be sure pedestal surface is flat, and shims cover entire area oftortion of housing. Undersized pillow block base.51 housing bore. See Illustration-Complaint A, Conditions 7-8-p-4 I-I I

Failure to remove chips, dirt,10 etc. from bearing housing be- Carefully clean housing, and use fresh lubricant.

fore assembling bearing unit.

Leather or composition seals Replace leather or composition seals with ones having reduced12 with excessive spring tension or spring tension. Lubricate seals.dried out. See IIIrfstr~rtinn-Conlplrl int .A* Cntlditiorz 12

13 Rotating seals rubbing against Check running clearance of rotating seal to elimina te rubbing.13-40 stationary parts. Correct alignment.See Illustratjon-Comp lajllt A, Condition I j-33-40

Insert gasket between housing and cover flange to relieve oxial15 Opposed mounting. pre-loading of bearing.See Illustration-Comp laint A, Cond itiarz I I

16 Two held bearings on one Back off covers in one of the housings, using shims to obtoin ade-13-24 shaft. Excessive shaft expansion. quate clearance of outer ring, to permit free oxial bearing motion.See Illustration-Comp laint A, Conditions 16-23-24

Loosen locknut and sleeve assembly. Retighten sufficiently to clamp19 Adapter tightened excessively. sleeve on shaft but be sure bearing turns freely.See Illustration-Com plaint A, Condition I9

39 Prong rubbing against bearing. Remove lockwasher. Straighten prong or replace w ith new washer.- See Il lwrtratiom-Com plaint A, Condition 19.31


35/42

:HARD TURNING OF SHUT - CornplaInt 0 (Continmd!

RR&OH ro l l C0NolY loN

causing bending of shaft.

Distortion of bearing seals.

shimming pillow blocks. Be sure shafts aren-specially when three or more bearings

Shaft and housing shoulders,

earing seat diameter machinedGrind shaft to get proper fit between inner ring of bearing

32


36/42


37/42

~

Applic ation Report No.592

Uq%U 600 U- ,4td/p t a . . .DETERMINE THE CONDITION OF

ANTI-FRICTION BEARINGS

by Robert E. Ellis

Balancing & Consulting Service Manager

IRD Corporation

INTERNATIONAL RESEARCH AND DEVELOPMENT CORPORATIONSubsidiary of H. H. Robertson Co.

6150 Huntley Road, Worthington, Ohio (Columbus) Phone 885-5376


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Using IRD Model 600 Vibration Analyzer to

DETERMINE THE CONDITION OF ANTI-FRICTION BEARINGS

How do you know when bearings are worn and need

to be replaced? Many times the answer is obvious

because of machine failure, poor quality in fin-ished parts, and unscheduled downtime. When

you dismantle you may find pits in the raceways

or on the balls or rollers. You may find flaked

areas, discoloration, broken retainers, dirt, cor-

rosion, and a host of others. If a faulty bearing

is continued in operation it always gets worse,

never better. The whole mac hine may become

noisy, the shaft may become loose and other parts

of the machine may fail.

Bearings with pitted or rough raceways and balls

impose forces on the cages when the rolling ele-

ments contac t the rough spots. These forces show

up as vibration in the machine structures. It is

these forces that result in decreased bearing life,

fatigue failure, heat and noise. Eventually, the

bearings become unserviceable. It is also these

forces that allow us to detect the bearings condi-

tion through vibration analysis before a costly

failure occurs. In many cases the minute vibra-

tions present in a machine structure closeto the

bearing contain the information needed to deter-

mine the bearings condition. Vibration is often

a good indicator of bearing performance. A high

vibration level can indicate damage by unbalance

or misalignment, excessive radial or axial load,

dirt and corrosion, or brinelling in assembly.

The IRD Vibration Analyzer can be used to ana-

lyze these and other vibrations so that a rapid

evaluation of the bearings condition may be ob-

tained and correc tive ac tion taken if needed.

Causes of Bearing Vibration

Sources of vibrations in bearings are:

1) Misalignment-two kindsa) Angular misalignment between inner and

outer races-the bearing rotates with the

inner ring at an angle to the shaft axis,

the balls will wear a track which wob-

bles from one side of the raceway to the

other. Common causes of this condition

are: shoulder out-of-square, burr between

the shoulder and bearing and fillet too

large.

Misalignment difficulties can also arise

when bearing housing shoulders are not

2)

3)

4)

5)

6)

b)

perpendicular to shaft axis or

is not in line with the housing.

the shaft

Angular and/or offset misalignment be-

tween different machine components ofa

system, such as a motor driving a fan

through a gear box. This condition refers

to misalignment between motor and gear-

box or gearbox and fan, and occurs when

the shaft axis is not parallel to the axis

tbrough the bearing centers.

Dirt or Foreign Matter-dirt or metal part-

icles in the lubricant or from flaking will be

pressed between the rolling elements of the

bearing and the raceway causing forces that

produce indentation and pits.

Lack of Lubrication-A dry bearing may pro-

vide excessive heat, rubbing bearing dis-

tortion showing up as vibration.

Corroded Parts-can start from: rust, oxi-

dation of lubricant, contaminating in-

fluence.

Pits-can be caused by corrosion or electri-

cal arcing. Electrical leakage may occur

through bearings from static electricity on

line shafts and in direct currentmotors.

Sparking at regular intervals burns away

metal leaving holes and pits.

Lack of Concentricity-usually becomesap-parantonly at a low level of vihration-may

show up as vibration at rotor speed. The

characteristics are such that it acts like

unbalance which shows up on one radial dir-

ection (horizontal, vertical, or at some other

specific angle). The equipment can gener-

ally be balanced to a low level of vibration

in one direction but will not show a low

level of vibration in another.

7) Pinch and Overload-bearings installed in

out-of-round housings or on out-of-roundshafts may distort enough to cause vibration

overload, and failure. Early fatigue failure

at opposite sides of the raceways may result.

8) Bearing-Retainer Rattle-loose retainers may

be a source of vibration.

9) Excessive Clearance-mostly found in sleeve


39/42

bearings. Can be detected by the difference

in amplitude readings taken on the bearing

housing and on the shaft. Shaft readings are

obtained by measuring directly on the shaft

running in the bearing, using a shaft stick.

10) Cracks in Rings and Parts-damage that has

occurred during installation through exces-

sive force, hammering or forcing the bearing

onto a tapered seat.

Analyzing Bearing Faults with the Model 600

Make all vibration measurements directly on thebearing housing as close to the bearing moving

parts as possible. One exception is when making

direct shaft measurements using the shaft stick.

Things to look for when analyzing bearing vibration:

Filter Out

1)

Many of the above conditions will show vibrations

in the axial direction on pre-loaded bearings.

Small erratic increases and decreases in am-

plitude meter reading. May be random or per-

iodic. Amount of vibration will depend on

severity of fault.

A rough anti-friction bearing where the roughness

js due to pits, holes, dirt, etc., results in a rela-tive high frequency of vibration. The vibration

frequency may be several times the frequency of

the rotating member which is mounted in the bear-

ing. The frequency of vibration may not be a direct

multiple of the shaft speed.

2)

3)

Unbalance and Critical Speeds

Both unbalance and operation at critical speed

will cause a rotating radial load, which consumes

some of the bearings capacity and which, if ex-

cessive, can lead to beoring failure. Balancing is

essential; and limits should be set such that the

unbalance load on the bearing is not more than

one-tenth of the bearing capacity at speed.

Apparent erratic or multiple firing of the

strob lamp. Reference mark on the shaft

will appear at several positions. May occur

as a multiple image slowly rotating. Strob

pattern appears related to shaft speed.

Apparent erratic frequency meter readings.Generally, the frequency meter will indicate

a much higher frequency than shaft speed.

Often the best frequency indications are ob-

tained using the velocity position.

Filter I n

1) Steady vibration displacement or velocity

readings-low amplitude-high frequency-

frequency indications not a direct multiple

of shaft speed. Velocity measurements us-

ually most useful.

Ball bearings will sometimes operate for limited

periods of time at or near a shaft critical speed,

provided that the critical speed is low. The effectof operation at a critical speed is unpredictable

because of the unknown damping factors, and it is,

therefore, best to keep the shaft critical speed

either well above operating speed or well below it.

High vibrations on bearings that are misaligned,

overloaded, etc., will show high frequency char-

acteristics as noted above.

2)

3)

Steady frequency meter indications at high

speeds. May or may not be direct multiples

of the shaft speed.

Variable vibration amplitude readings-rel-

atively low amplitude-high frequency. Am-

plitude readings beats or slowly varies

up and down. Frequency meter steady. Fre-

quency may or may not be a direct multiple

of the shaft speed.

C AUTION

Large forces due to unbalance of rotating parts

or misalignment moy mask many bearing trou-

bles. Unbalance, misalignment, loose, and

damaged parts must be corrected before bear-

ing analysis is attempted. Balance the rotat-

ing parts to a low vibration level if required.

The vibrations due to rough bearings are easily

distinguished from high frequency electricalvib-

rations .Vibrations due to rough hearings will

continue after the electrical power has been shut

off and while the rotating member is coasting toa

stop. Vibrations from electrical causes, however,will cease immediately when the electrical power

is shut off.

The information given below describes the use of Use of an Oscilloscope

the IRD Model 600 Vibration Analyzer for analyzing An Oscilloscope connected to the scope outlet

bearing faults. jack of the IRD Vibration Analyzer will allow a


40/42

-

direct visualobservation of the bearing vibration

pattern as measured at the pickup location. Thepresence of high frequency noise and hash,spike-like pulses or erratic and rapid changes in ampli-

tude are bearing condition indicators. Either dis-

placement or velocity may be used but velocitymeasurements usually give better high frequency

indications

The higher the speed, the more sensitive the bear-ing is to theadverse effects of misalignment, poor

lubrication, improper fitting practice, poor heatdissipation and contamination.

IRD #592


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DOS AND DONTS FOR BEARINGS. . . assembly, maintenance, inspection and lubrication

Do work as close to the ideal conditions pictured here.

Dividends in beoring performance will result.

Dont work under the handicap of poor tools, rough

bench, plenty of dirt.

DO work with clean tools, in clean surroundings.

DO remove all outside dirt from housing before

exposing bearings.

DO handle with-clean, dry hands.

DO treat a used bearing as carefully as a new one.

DO use clean solvents and hushing oils.

DO lay bearings out on clean paper.

DO protect disassembled bearings from dirt and

moisture.

DO use clean, lint-free rags if beorings are wiped.

DO keep bearings wrapped in oil-proof paper when

not in use.

DO clean inside of housing before replacing bearings.

DO install new bearings as removed from packages,

without washing.

DO keep bearing lubricants clean when applying and

cover containers when not in use.

DONT work in dirty surroundings.

DONT use wooden mallets or work on rough or dirty

bench tops.

DONT use dirty, brittle or chipped tools.

DONT handle bearings with dirty, moist hands.

DONT spin uncleaned bearings.

DONT spin any bearings with compressed air.

DONT use same container for cleaning and final

rinsing of bearings.

DONT use cotton waste or dirty c loths to wipe

bearings.

DONT expose bearings to moisture or dirt at any

ti

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