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Technical
Technical
Information
Information
●Classification and Characteristics of Rolling
Bearings
1. Classification and Characteristics of Rolling Bearings
1.1 and
Rolling
bearing construction
Classification
Characteristics
of Rolling Bearings
Most rolling bearings consist of rings with raceway
1.1 Rolling(inner
bearing
ring construction
and outer ring), rolling elements (either balls or
and consist
cage. The
cage separates
the rolling
Most rollingrollers)
bearings
of rings
with raceway
(inner
elements
regular
intervals,(either
holds them
within
ring and outer
ring), at
rolling
elements
balls inorplace
rollers)
the inner
outer raceways,
andelements
allows them
to rotate
and cage. The
cageand
separates
the rolling
at regular
freely.them in place within the inner and outer
intervals, holds
raceways, and
allows
them
to and
rotate
freely.
Raceway
(inner
ring
outer
ring) or raceway washer 1)
Outer ring
Outer
ring
Inner ring
Inner
ring
Cage
Ball
The surface on which rolling elements roll is called the
"raceway
surface".
The load
on the bearing
is 1)
Raceway (inner
ring
and outer
ring)placed
or raceway
washer
this contact
surface.
The surfacesupported
on whichbyrolling
elements
roll is called the
Generally
theload
inner
ring fitson
onthe
thebearing
axle or shaft
“raceway surface”.
The
placed
is and the
outer ring on the housing.
Deep groove ball bearing
Fig A
supported by
this contact surface. Generally the inner ring fits
Note 1: The raceway of thrust bearing is called "raceway washer,"
on the axle or shaft
outer
on the
housing.
1:
theand
inner the
ring is
calledring
the "shaft
raceway
washer"Note
and the
outer ring
is called
"housing
raceway washer."
The raceway of thrust
bearing
isthe
called
“raceway
washer,” the
inner ring isRolling
called elements
the “shaft raceway washer” and the outer
ring is called Rolling
the “housing
raceway
elements
classify washer.”
in two types: balls and rollers.
Rollers come in four types: cylindrical, needle, tapered,
Rolling elements
and spherical.
Ballsclassify
geometrically
theand
raceway
surfaces of
Rolling elements
in twocontact
types:with
balls
rollers.
theininner
outercylindrical,
rings at "points",
while
the contact
Rollers come
fourand
types:
needle,
tapered,
surface
of geometrically
rollers is a "line"contact
contact.with the raceway
and spherical.
Balls
Theoretically,
rolling rings
bearings
are so constructed
surfaces of the
inner and outer
at “points”,
while theas to
allow
the
rolling
elements
to
rotate
orbitally
while also
contact surface of rollers is a “line” contact. Theoretically,
rotating on their own axes at the same time.
Ball
Cage
Angular contact ball bearing
Fig.B
Outer ring
Outer ring
Inner ring
Roller
Cage
Cage
Roller
rolling bearings are so constructed as to allow the rolling
elements toCages
rotate orbitally while also rotating on their own
Cagestime.
function
to maintain
rolling elements
at a uniform
axes at the same
Cages
Cages function
to maintain
pitch so
is never
applied
directly
to the cage
and to
rolling elements
at load
a uniform
pitch
so load
is never
applied
prevent
rolling
elements
from
falling
out when
directly to the
cagethe
and
to prevent
the
rolling
elements
handling the bearing. Types of cages differ according to
from falling out when handling the bearing. Types of cages
way they are manufactured, and include pressed,
differ according
to way
arecages.
manufactured, and include
machined
andthey
formed
pressed, machined and formed cages.
Cylindrical roller bearing
Fig. C
Needle roller bearing
Fig. D
Outer
ring
Outer ring
Roller
Inner
ring
Cage
1.2 Classification
of rolling bearings
1.2 Classification
of rolling bearings
Rolling bearings
divide
into two
main
ball
Rolling
bearings
divide
into classifications:
two main classifications:
ball
bearings
and roller bearings.
Ball bearings
are classified
bearings and
roller bearings.
Ball bearings
are classified
according
to theirring
bearing
ring configurations:
deep
according to
their bearing
configurations:
deep groove
groove contact
type andtype.
angular
contact
type. Roller
bearings
type and angular
Roller
bearings
on the
other on
the other according
hand are classified
according
to the
shape of
hand are classified
to the shape
of the
rollers:
the rollers: cylindrical, needle, tapered and spherical.
cylindrical, needle, tapered and spherical. Rolling bearings
can be further
classified according to the direction in which
Rolling bearings can be further classified according to
the load is applied;
radial
bearings
carry
radial loads
the direction
in which
the load
is applied;
radialand
bearings
thrust bearings
carry
axial
loads.
carry radial loads and thrust bearings carry axial loads.
Other classification methods include: 1) number of rolling
rows (single, Other
double,
or 4-row),methods
2) separable
and
non- of
classification
include:
1) number
rolling
rows
(single,
or 4-row),
separable
and
separable, in
which
either
thedouble,
inner ring
or the2)outer
ring can
non-separable,
in which
eitherdesigned
the inner ring
or the outer
be detached.
There are also
bearings
for special
ring
can as:
be detached.
applications,
such
railway car journal roller bearings, ball
screw support bearings, turntable bearings, as well as linear
There are also bearings designed for special
motion bearings
(linear ball bearings, linear roller bearings
applications, such as: railway car journal roller bearings,
and linear flat roller bearings).Types of rolling bearings are
ball screw support bearings, turntable bearings, as well
given in Fig.as1.2.
linear motion bearings (linear ball bearings, linear
Roller
Cage
Inner ring
Tapered roller bearing
Fig. E
Shaft raceway washer
Spherical roller bearing
Fig. F
Shaft raceway washer
Roller
Ball
Cage
Cage
Housing raceway washer
Thrust ball bearing
Fig. G
roller bearings and linear flat roller bearings).Types of
rolling bearings are given in Fig. 1.2.
Housing raceway washer
Thrust roller bearing
Fig. H
Fig. 1.1 Rolling bearing
A-5
201 Brighton Avenue • Boston, MA 02134 • Ph: 800.225.4587 • Fx: 800.252.1996 • www.emersonbearing.com
201 Brighton Avenue • Boston, MA 02134 • Ph: 800.225.4587 • Fx: 800.252.1996 • www.emersonbearing.com
1.3 Characteristics of rolling bearings
1.3.11.3
Characteristics
of rolling
bearings
Characteristics
of rolling
bearings
Rolling bearings come in many shapes and varieties,
rolling bearings
each1.3.1
with Characteristics
its own distinctiveoffeatures.
Rolling
bearings
comewith
in many
shapes
and rolling
varieties,
However,
when
compared
sliding
bearings,
each
with
its
own
distinctive
features.
bearings all have the following advantages:
However, when compared with sliding bearings, rolling
all have
the coefficient
following advantages:
(1)bearings
The starting
friction
is lower and there is
1.3 Characteristics of rolling bearings
little difference between this and the dynamic
1.3.1 Characteristics of rolling bearings
(1) Thecoefficient.
starting friction coefficient is lower and there is
friction
Rolling bearings come in many shapes and varieties, each
little
difference between
this and
the dynamic
(2)with
They
are
internationally
standardized,
interchangeable
its own distinctive features.
However,
when compared
friction
coefficient.
andsliding
readily
obtainable.
with
bearings,
rolling bearings all have the following
(2) They
internationally
(3)advantages:
They
are are
easy
to lubricate standardized,
and consumeinterchangeable
less
and
readily
obtainable.
lubricant.
(1) The starting friction coefficient is lower and there is little
(3)aThey
are rule,
easy
toand
lubricate
and
consume
less
(4)difference
As
general
one
bearing
can carry
bothcoefficient.
radial
between
this
the dynamic
friction
lubricant.
(2)and
They
are internationally
standardized,
interchangeable and
axial
loads at the same
time.
obtainable.
(4) As
aused
general
rule, high
one bearing
can carry both radial
(5)readily
May
be
in either
or low temperature
(3)applications.
They
areaxial
easyloads
to lubricate
consume
and
at the and
same
time. less lubricant.
As May
a general
rule,
one
bearing
carry
both radial and
(5)
be used
in
either
highcan
orby
low
temperature
(6)(4)Bearing
rigidity
can
be
improved
preloading.
axial loads
at the same time.
applications.
(5) (6)
May
be usedrigidity
in either
high
low temperature
Bearing
can
be or
improved
by of
preloading.
Construction,
classes, and
special
features
rolling
applications.
bearings are fully described in the boundary dimensions
(6) Bearing rigidity can be improved by preloading.
Construction,
classes,
andsection.
special features of rolling
and bearing
numbering
system
bearings
are
fully
described
in
thefeatures
boundary
dimensions
Construction, classes, and special
of rolling
bearings
and
bearing
numbering
system
section.
1.3.2are
Ball
bearings
and
roller
bearings
fully
described
in the
boundary
dimensions and bearing
Table
1.1 gives
a comparison
numbering
system
section. of ball bearings and roller
1.3.2 Ball bearings and roller bearings
bearings.
Table
gives aand
comparison
of ball bearings and roller
1.3.2
Ball1.1
bearings
roller bearings
Table
1.1 gives a comparison of ball bearings and roller
bearings.
Table
1.1 Comparison of ball bearings and roller bearings
bearings.
They also have superior
acoustic characteristics.
Load capacity is lower for
Load capacity is higher for
ball bearings, but radial
rolling bearings. Cylindrical
bearings
capable
bearings
equipped
withfor
Loadare
capacity
is of
lower for rollerLoad
capacity
is higher
bearing
loads
in
both
the
a
lip
can
bear
slight
radial
ball bearings, but radial
rolling bearings. Cylindrical
radialbearings
and axialare
direction.
Combining
tapered
capable of loads.roller
bearings
equipped with
roller
in pairs
bearing loads in both the
abearings
lip can bear
slight radial
enables
the
bearings
bear
radial and axial direction.
loads. Combiningtotapered
an axial
load
in
both
directions.
roller bearings in pairs
Table 1.2 Configuration of sealed ball bearings
Shield
Sealed
Type
Table 1.2 Configuration of sealed ball bearings
and
Non-contact Non-contact
Contact
Low torque
symbol
ZZ Shield
LLB
LLUSealed
LLH
Type
and
Non-contact Non-contact
Contact
Low torque
symbol
ZZ
LLB
LLU
LLH
enables the bearings to bear
an axial load in both directions.
A-8
A-8
Configuration
Characteristics
load of
is point
applied.
rectangular
load is
Because
of linearwhen
contact,
Because
contact
applied.
rotational
torque is higher for
there is little rolling
bearings of
than
for contact,
ball
resistance,
ballofbearings
are rollerBecause
linear
Because
point contact
bearings,
but
rigidity
is
also
suitable
for
low
torque
and
rotational torque is higher for
there is little rolling
higher.
high-speed
applications.
roller bearings than for ball
resistance,
ball bearings are
Theysuitable
also have
superior
bearings, but rigidity is also
for low torque and
acoustic
characteristics.
higher.
high-speed applications.
Load capacity
Load capacity
Characteristics
Point contact
Linear contact
Contact surface is2aoval when Contact surface is r
generally
load is
applied.
rectangular
load is
Point
contact
Linear when
contact
applied.
Contact surface is oval when
Contact surface is generally
The
typeshield
of bearing,
deep
Deep
groove
ballcommon
bearings
groove
ballmost
bearings
include
bearings
andgroove
sealedball
The
most
common
typemake
ofused
bearing,
deep
groove
ball Deep
bearings
are
widely
in aeasier
variety
fields.
bearings
with
grease
them
toofuse.
bearings
are ball
widely
used
ininclude
a variety
of fields.
Deep groove
groove
bearings
bearings
and
sealed
Deep
groove
ball
bearings
alsoshield
include
bearings
with
a
ball
bearings
include
shield
bearings
and
sealed
bearings
with grease
make
them easier
tobearings
use.
locating
snap-ring
to facilitate
positioning
when
mounting
with
grease
make
them
to use.
Deep
groove
ball
Deep
groove
balleasier
bearings
also
include
bearings
the outer
ring,
expansion
compensating
bearings
whichwith a
bearings
also snap-ring
include bearings
with apositioning
locating snap-ring
to
locating
to
facilitate
when
mounting
absorb dimension variation of the bearing fitting surface
facilitate positioning when mounting the outer ring, expansion
outer ring,
expansionand
compensating
bearings
which
due the
to housing
temperature,
TAB bearings
that are
compensating bearings which absorb dimension variation of
absorb
dimension
variation of
the
bearing
fitting
surface
able
to
withstand
contamination
in
the
lubricating
oil.
the bearing fitting surface due to housing temperature, and
to housing
and TAB
bearings in
that
TAB due
bearings
that aretemperature,
able to withstand
contamination
theare
able
to
withstand
contamination
in
the
lubricating
oil.
lubricating oil.
Configuration
2b
2b
r
2a
and “unit bearings” which are integrated (built-in) into
a machine’s components,
and other
designed
Deep groove
ball specially
bearings
bearings are also available. The feature of typical standard
The most
type
of bearing,
groove ball
bearings
are common
as follows:
Deep
groove
balldeep
bearings
bearings are widely used in a variety of fields. Deep
Roller bearings
2b
Ball bearings
2b
Contact with
raceway
Contact with
raceway
Roller bearings
bearings of ball bearings
Table 1.1Ball
Comparison
and roller bearings
1.3.3 Radial and thrust bearings
Almost all types of rolling bearings can carry both radial
Radial
thrusttime.
bearings
and 1.3.3
axial loads
at and
the same
Almostbearings
all types with
of rolling
bearings
carrythan
both radial
Generally,
a contact
anglecan
of less
and axial
loads
at theradial
sameload
time.capacity and are
45°have
a much
greater
Generally,
a contact
anglewhich
of less
than
classed
as radial bearings
bearings;with
whereas
bearings
have
45°
have
a
much
greater
radial
load
capacity
and
are
a contact angle over 45°have a greater axial load
classed
bearings;
whereas
bearings
capacity
andas
areradial
classed
as thrust
bearings.
Therewhich
are have
contact angle
over
have bearings
a greater which
axial load
alsoabearings
classed
as 45°
complex
1.3.3capacity
Radial and
bearings
andthrust
are characteristics
classed
as thrust
bearings.
combine the loading
of both
radialThere
and are
Almost all types of rolling bearings can carry both radial and
also
bearings classed as complex bearings which
thrust
bearings.
axial loads at the same time.
combine the loading characteristics of both radial and
Generally, bearings with a contact angle of less than 45°have
thrust
bearings.
Standard
bearings
and special
a1.3.4
much
greater
radial
load capacity
and arebearings
classed as radial
The boundary
and have
shapes
of bearings
bearings;
whereasdimensions
bearings which
a contact
angle over
1.3.4a greater
Standard
and and
special
bearings
conforming
to international
standards
are
45°have
axialbearings
load capacity
areinterchangeable
classed
as
The
and shapes
bearings
and can
beboundary
obtained
easily
economically
over
the
thrust
bearings.
There dimensions
are
alsoand
bearings
classedof
as
complex
conforming
to international
standards
are interchangeable
bearings
which
thebetter
loading
characteristics
of both
world
over.
It iscombine
therefore
to design
mechanical
radial
andcan
thrust
bearings.
and
obtained
easily
and economically over the
equipment
tobe
use
standard
bearings.
world over. It is therefore better to design mechanical
1.3.4
Standard
bearings
and
equipment
to use standard
bearings.
However,
depending
on
thespecial
type
ofbearings
machine they are to
The
boundary
dimensions
and
shapes
of bearings
be used in, and the expected application
and function, a
conforming
to international
are of
interchangeable
However,
on the type
machine
non-standard
or depending
specially standards
designed
bearing
may bethey
bestare to
and can be obtained easily and economically over the world
be used
in, and
and function, a
to use.
Bearings
thatthe
areexpected
adapted application
to specific applications,
over. It is therefore better to design mechanical
orwhich
specially
designed bearing
and non-standard
"unit bearings"
are integrated
(built-in)may
intobe
a best
equipment
to use standard
bearings.
to use.components,
Bearings thatand
areother
adapted
to specific
applications,
machine's
specially
designed
and "unit
bearings"
which
integrated
(built-in)
into a
bearings
are also
available.
However,
depending
on the
typeare
of machine
they
are to be
machine's
and other
The
typical standard
bearings
are asdesigned
used
in,feature
and theofcomponents,
expected
application
andspecially
function,
afollows:
nonbearings
are also
available.
standard
or specially
designed
bearing may be best to use.
The
feature
of typical
standard
bearings are as follows:
Bearings
that
are adapted
to specific
applications,
●Classification and Characteristics of Rolling Bearings
Angular contact ball bearings
Cylindrical roller bearings
Angular
ball
bearings
The line that unites
pointcontact
of contact
of the
inner ring,
ball and outer ring runs at a certain angle (contact angle)
The line that unites point of contact of the inner ring,
in the ball
radial
direction.
generally
and
outer ringBearings
runs at aare
certain
angle designed
(contact angle)
contact
ball bearings
with Angular
three
contact
angles.
in the radial direction. Bearings are generally designed
The line
that unites
point of contact
of the inner ring, ball and
Angular
ball bearings
with contact
three contact
angles. can support an axial load,
outer ring
runs
atby
a certain
angle (contact
angle) in the radial
but cannot
be
used
single
bearing
because
Angular contact ball bearings can supportofanthe
axial load,
direction.
Bearings
are
generally
designed
contact
They
mustbyinstead
be usedbecause
in with
pairsthree
or the
incontact
butangle.
cannot
be used
single bearing
of
angles. Angular contact ball bearings can support an axial
combinations.
contact angle. They must instead be used in pairs or in
load,
Angular
contact ball bearings include double row
combinations.
but
cannot be used by single bearing because of the contact
Angular
ball bearings
include
double
row
angular
contact
ball bearings
forused
which
the inner
angle.
They contact
must
instead
be
in pairs
or in and
combinations.
angular
contact
ball
bearings
for
which
the
inner
and
outerAngular
rings
are
combined
as
a
single
unit.
The
contact
contact ball bearings include double row angular
outer
rings
are
combined
as
a
single
unit.
The
contact
angle
of
double
row
angular
contact
ball
bearings
is
contact ball bearings for which the inner and outer 25˚.
rings are
angle
double
row unit.
angular
ball
bearings
is 25˚.
There
are of
also
four-point
contact
bearings
that
combined
as a
single
Thecontact
contact
angle
ofcan
double
row
There
areload
also
contact
bearings
that can
support
an axial
infour-point
both directions
by
themselves.
angular
contact
ball
bearings
is 25°. There
are also
foursupport
an however
axial
loadrequire
in both
directions
byaxial
themselves.
point
contact
bearings
that
cancaution
supportbecause
an
load in both
These
bearings
These
bearings
however
require
caution
because
directions
by
themselves.
These
bearings
however
problems such as excessive temperature rise and require
problems
such problems
as
excessive
temperature
rise
and
caution
because
such
as
temperature
wearing
could
occur
depending
on
theexcessive
load conditions.
Cylindrical
roller and
bearings
Uses rollers for
rolling elements,
therefore has a
high load capacity. The rollers are guided by the ribs of
Uses rollers for rolling elements, and therefore has a
thehigh
inner
or capacity.
outer ring.
The
innerare
and
outerby
rings
can of
be
load
The
rollers
guided
the ribs
Cylindrical to
roller
bearings
separated
facilitate
assembly,
and
both
can
be
fit
with
the inner or outer ring. The inner and outer rings can be
Uses rollers
for rolling
elements,
therefore
has a high
shaft
or housing
tightly.
If thereand
is and
no
ribs,
inner
separated
to facilitate
assembly,
botheither
can bethe
fit with
load
capacity.
Thecan
rollers
are freely
guidedinby
the
ribs direction.
of the inner
or
the
outer
ring
move
the
axial
shaft or housing tightly. If there is no ribs, either the inner
or outer ring.
The bearings
inner and are
outer
rings canideal
be separated
Cylindrical
roller
therefore
to be used
or the outer
ring can move
freely
in the axial direction.
to facilitate assembly, and both can be fit with shaft or
as Cylindrical
so-called "free
side
bearings"
that absorb
shaft
roller
bearings
are
therefore
ideal
used
housing tightly. If there is no ribs, either the innertoorbe
the
expansion.
In
the
case
where
there
is
a
ribs,
the
bearing
as
so-called
"free
side
bearings"
that
absorb
shaft
outer ring can move freely in the axial direction. Cylindrical
expansion.
In
the
case
where
there
a ribs,
thethe
bearing
can
bear
a slight
axial
load
between
the
end
rollers
roller
bearings
are
therefore
ideal
to be is
used
as of
so-called
can
bear
a
slight
axial
load
between
the
end
of
the
rollers
and
the
ribs.
Cylindrical
roller
bearings
include
the
HT
“free side bearings” that absorb shaft expansion. In the case
and
the ribs.
roller bearings
include
HTload
type
which
modifies
the bearing
shape
of
roller
facethe
and
ribs
where
there
is aCylindrical
ribs, the
can
bearend
a slight
axial
type
which
modifies
the
shape
roller
end
ribs
for
increasing
axial
road
capacity.
And
the
Eface
typeand
with
a
between
the end
of the
rollers
andofthe
ribs.
Cylindrical
roller
for increasing
axial
road
And
the the
Eload
type
withofa
special
internal
for capacity.
enhancing
radial
capacity.
bearings
include design
the HT
type
which modifies
shape
special
internal
enhancing
radial
capacity.
roller
face
anddesign
ribs forfor
increasing
axial
roadload
capacity.
And
The
Eend
type
is standardized
for small-diameter
sizes.
The
E
type
is
standardized
for
small-diameter
sizes.
the
E
type
with
a
special
internal
design
for
enhancing
radial
Table 1.6 shows the basic configuration for cylindrical
Table
1.6 shows
basic
configuration
cylindrical
load
capacity.
The Ethe
type
is standardized
forfor
small-diameter
roller
bearings.
wearing
could occur
on the load
conditions.
rise
and wearing
coulddepending
occur depending
on the
load
conditions.
roller
bearings.
sizes.
Table
1.6 shows the basic configuration for cylindrical
roller
bearings.
In addition to these, there are cylindrical roller bearings
In addition to these, there are cylindrical roller bearings
with
multiple rows
ofofrollers
and
the SL type
of
full
with multiple
rowsthere
rollers
and the SLroller
typebearings
of full with
In addition
to these,
are cylindrical
complement
roller
bearing
without
cage.
complement
bearing
without
cage.
multiple
rows ofroller
rollers
and the
SL type
of full complement
roller bearing without cage.
Table 1.3 Contact angle and symbol
Table 1.3 Contact angle and symbol
ContactContact
angle angle
Contact
angleangle
and contact
angle
symbol
Contact
and contact
angle
symbol
Table
1.61.6
Types
ofof
cylindrical
Table
Types
cylindricalroller
rollerbearings
bearings
Contact
angleangle 15°15°30°30° 40°40°
Contact
Contact
angleangle
Contact
C
symbol
symbol
A
C
1）
A
1）
B
Type
Type
and
and
Symbol
Symbol
B
NUNU
type
type
NN
type
type
NJ
NJtype
type
NF
NFtype
type
NUP
type
NUP type
type
NH type
（NJ+HJ）
（NJ+HJ）
type
NUNU
type
NJtype
type
NJ
NUP type
NUP
type
1: Contact
symbol
has been
abbreviated
Note 1:Note
Contact
angle angle
symbol
has been
abbreviated
as "A".as "A".
Configuration
Configuration
symbol
Non-contact Contact
Contact
ShieldNon-contact
sealed
sealed
Shield
sealed
sealed
ZZ
LLM
LLD
ZZ
LLM
LLD
N type
N type
Table 1.5 Combinations of duplex angular contact ball bearings
Table 1.5 Combinations of duplex angular contact ball bearings
Type
Back-to-back
Configuration
duplex
andBack-to-back
Type symbol
duplex DB
and
symbol
DB
Configuration
Drawings
Type Type
and
and symbol
Open Open
Drawings
Table
1.4 Configuration
of double
row angular
contact
bearings
Table 1.4
Configuration
of double
row angular
contact
ball ball
bearings
Face-to-face
duplex
Face-to-face
duplexDF
DF
r
r
Tandem duplex
DT
Tandem duplex
DT
r
r
A-9
A-9
NF type
NF type
NH type
NH type
●Classification and Characteristics of Rolling Bearings
Tapered roller bearings
Spherical roller bearings
TaperedTapered
roller bearings
arebearings
designed so the inner/outer
roller
ring raceway and apex
of theroller
tapered
rollers intersect at
Tapered
bearings
Tapered
roller
are centerline.
designed so
inner/outer
one point
onbearings
the bearing
Bythe
receiving
roller bearings are designed so the inner/outer
ring combined
racewayTapered
and
apex
the tapered
rollers
at are
load
fromofinner
and outer
ring,intersect
the rollers
ringroller
raceway
and apex of the tapered rollers intersect at
bearings
one Tapered
point on
the
bearing
centerline.
By
receiving
pushed
against
the
inner
ring
rib
and
roll
guided
with
rib.
one point on the bearing centerline. By receiving
Tapered
roller
bearings
are designed
sothe
thedirection
inner/outer
ringa
combined
load
from
inner
and
outer
ring,
rollers
are
Induced
force
is
produced
in
the
axial
when
combined load from inner and outer ring, the rollers are
raceway
andisthe
apex
of the
tapered
rollers
intersect
at rib.
one
point
pushed
against
inner
ring
rib ring
and
roll
guided
with
radial
load
applied,
soinner
must
be
handled
using
a rib.
pair
pushed
against
the
rib
and
roll by
guided
with
on
the
bearing
centerline.
By
receiving
combined
load
from
Induced
force
isThe
produced
in the
when
a a
of bearings.
inner
ring
withaxial
rollers
anddirection
outer
ring
Induced
force
is produced
in
thedirection
axial
when
inner and outer ring, the rollers are pushed against the inner
load
is facilitating
applied,
be handled
by using
a pair
radial
loadradial
is applied,
so
mustso
bemust
handled
by
using
a pair
come
apart,
thus
mounting
with
clearance
or
ring ribofand
roll guided
with ring
rib. Induced
force
isouter
produced
bearings.
inner
with
rollers
andhard
of bearings.
The
innerThe
ring
with rollers
and outer
ringtoring
preload.
Assembled
clearance
is
however
in the come
axial direction
when
a radial
load is applied,
so must
apart,
thus
facilitating
mounting
with clearance
come
apart,
thus
mounting
withThe
clearance
or or
manage
and
requires
special
attention.
Tapered
roller
be
handled
byfacilitating
using a pair
of bearings.
inner
ring
preload.
Assembled
clearance
is
however
hard
to with
preload.
Assembled
clearance
is
however
hard
to
bearings
are
capable
of
supporting
large
loads
in
both the
rollersmanage
and outer
ring
come special
apart, thus
facilitating
mounting
and
requires
attention.
Tapered
roller
manage
and
requires
special
attention.
Tapered
roller
axial
and
radial
directions.
with clearance
or preload.
is in
however
bearings are
capable Assembled
of supportingclearance
large loads
both the
bearings
are
capable
of requires
supporting
large
loads
inTapered
bothtothe
NTN
bearings
with
4T-, ET-,
Tand
U attached
the
hard
to
manage
and
special
attention.
roller
axial
and radial
directions.
axialbearings
and radial
aredirections.
capable
of
supporting
large
in both
name
conform
to ISO
and
JISET-,
standards
sub-unit
NTN
bearings
with
4T-,
Tandloads
U for
attached
tothe
the
axial
and
radial
directions.
NTN
bearings
with
4T-,
ET-,
T- and
U attached
to
theend
dimensions
(nominal
angle,
nominal
name
conform
to contact
ISO and
JIS standards
forsmall
sub-unit
NTN
bearings
with(nominal
4T-, ET-,
T-are
and
U attached
tosmall
the name
dimensions
contact
angle,
nominal
end
name
conform
ISO
and
JIS
standards
for
sub-unit
diameter
oftoouter
ring)
and
internationally
conform
to
ISO
and
JIS
standards
for
sub-unit
dimensions
diameter
of
outer
ring)
and
are
internationally
dimensions
(nominal
contact
angle,
nominal
small
end
interchangeable.
(nominal
contact
angle,
nominal
small end diameter
of outer
interchangeable.
diameter
of
outer
ring)
andof
are
internationally
NTN
also
has
a
line
case
hardened
steel bearings
ring)
and
are
internationally
interchangeable.
NTN
also
has
a
line
of
case
hardened
steel
bearings
interchangeable.
designed for longer life (ETA-, ET-, etc.). NTN tapered
designed
life hardened
(ETA-, ET-,
etc.).
NTN tapered
NTN also
has a for
linelonger
case
steel
bearings
NTN
also
has
a line
ofofinclude
case
hardened
steel
bearings
roller
bearings
also
bearings
with
two
and four
rollerforbearings
also(ETA-,
include
bearings
with tapered
two and four
designed
longer life
ET-,
etc.). NTN
roller
designed
for
longer
life
(ETA-,
ET-,
etc.).
NTN
tapered
rows
of
tapered
rollers
for
extra-heavy
loads.
rows
of tapered
for extra-heavy
loads.
bearings
also
include rollers
bearings
with two and
four rows of
rollertapered
bearings
alsofor
include
bearings
with two and four
rollers
extra-heavy
loads.
rows of tapered rollers for extra-heavy loads.
Equipped
with an outer
ringbearings
with a spherical raceway
Spherical
roller
surface andSpherical
an inner ring
which
holds two rows of barrelroller
bearings
Equipped
anelements,
outer ring NTN
with a
spherical
raceway
shaped with
rolling
spherical
roller
bearings
Equipped with an outer ring with a spherical raceway
surface
which
holds two
rows of inclination
barrelare and
ablean
to inner
adjustring
center
alignment
to handle
of
surface roller
and anbearings
inner ring which holds two rows of barrelSpherical
shaped
rolling
elements,
NTN
spherical
roller
bearings
the
axle
or
shaft.
shaped rolling elements, NTN spherical roller bearings
Equipped
an variety
outer
ring bearing
with a spherical
raceway
surface
are
able
towith
adjust
center
tohandle
handle
inclination
There
are
types
that
differ
according
are
able
to
adjust
centerofalignment
alignment to
inclination
of of
and axle
an
inner
ringdesign.
which holds two rows of barrelshaped
the
or or
shaft.
to axle
internal
the
shaft.
rolling
elements,
NTNofspherical
roller
bearings
areaccording
able to
There
areare
variety
bearing
types
thatas
differ
Spherical
rollerofbearings
include
type
equipped with
There
variety
bearing types
that
differ
according
adjust center alignment to handle inclination of the axle or
toan
internal
design.
to internal
design.
inner
ring with a tapered bore. The bearing can easily
shaft.Spherical
There areroller
variety
of bearing
types
thatequipped
differ according
bearings
include
as
with
Spherical
rolleron
bearings
astype
type
equipped
with
be
mounted
a shaftinclude
by means
of an
adapter
or
to internal
design.
Spherical
roller
bearings
include
as
type
an
inner
ring
with
a
tapered
bore.
The
bearing
can
easily
an
inner
ring
with
a
tapered
bore.
The
bearing
can
easily
withdrawal
sleeve. The bearing is capable of supporting
equipped
with
be
mounted
shaftby
by means
means of
an
or
be
mounted
ononaaashaft
of
anadapter
adapter
heavy
and
is therefore
often
usedcan
in or
industrial
an inner
ringloads,
with
tapered
bore. is
The
bearing
easily
be
withdrawal
sleeve.
The bearing
capable
of supporting
withdrawal
sleeve.
The
bearing
is
capable
of
supporting
machinery.
When
heavy
axial
load
is
applied
to the
mounted
on a shaft
bytherefore
means ofoften
an adapter
or withdrawal
heavy loads,
and is
used in industrial
heavy
loads,
and
isis
therefore
often
inheavy
industrial
bearing,
the
load
on rollers
of another
row
isloads,
disappeared,
sleeve.
The bearing
capable
supporting
machinery.
When
heavy
axialof
load
isused
applied
to the
machinery.
When
heavy
axial
load
is row
applied
to
the
andbearing,
is
therefore
often
used
inof
industrial
machinery.
When be
and
can
cause
problems.
Attention
must
therefore
the
load
on
rollers
another
is disappeared,
heavy
axial
load
isproblems.
applied
to
theanother
bearing,
the
on
bearing,
the
load
on
rollers
of
isload
disappeared,
paid
tocause
operating
conditions.
and
can
Attention
mustrow
therefore
be rollers
of another
row isproblems.
disappeared,
and can
cause
problems.
paid
operating
conditions.
and
cantocause
Attention
must
therefore
be
Table 1.7 Types of spherical roller bearings
Attention
must therefore
be paid to operating conditions.
paid
to
operating
conditions.
Table 1.7 Types of spherical roller bearings
Standard
Table Type
1.7 Types
of spherical roller
bearings213 type
C type
E type
Standard
(B type)
Type
C type
213 type
E type
(B type)
Standard
(B type)
Configuration
Configuration
Configuration
Type
C type
213 type
E type
Thrust bearings
Thrust bearings
Thrust
bearings
There
are many types of thrust bearings that differ
There
are
many
of
thrustand
bearings
differ
There
are
many
types
oftypes
thrustbearings
bearings
that
differthat
according
Thrust
according
to
shape
of
rolling
element
application.
to shape
of rolling
element
application.
according
to shape
ofand
rolling
element
andspecial
application.
Allowable
rotational
speed
is generally
low Allowable
and
rotational
speed
isbegenerally
low
and
special attention
attention
must
paid toof
lubrication.
There
are
many
types
thrust
that
Allowable
rotational
speed
is bearings
generally
low differ
and special
mustattention
be paid
to
lubrication.
to
theapplication.
ones given
according
to shape
of rolling
element
and
must
be
paidIntoaddition
lubrication.
In there
addition
the ones
given
below,
areand
various
below,
aretovarious
types
thrustthere
bearings
forspecial
special
Allowable
rotational
speed
is of
generally
low
types ofmust
thrust
bearings
forlubrication.
special
applications.
Fortodetails,
applications.
For
details,
see
the
catalog
devoted
attention
be
paid
to
In addition to the ones given below, there arethe
various
see the catalog
concerned
type ofdevoted
bearing.to the concerned type of bearing.
Sub-unit dimensions
Sub-unit dimensions
2α
2α
E
types of thrust bearings for special applications. For details,
of thrust
bearings
InTable
addition
to the
ones
giventobelow,
there aretype
various
see1.8
theTypes
catalog
devoted
the concerned
of bearing.
Single
direction
thrust
ball
types
of
thrust
bearings
for
special
applications.
For
details,
Type
Needle roller thrust bearing
bearing
Table 1.8 Types
of thrust bearings
see the
catalog devoted
to the concerned type of bearing.
E
E
E : nominal small end diameter of outer ring
α : Nominal contact angle
Type Single direction thrust ball
bearing
Table 1.8 Types of thrust
bearings
E : nominal small end diameter of outer ring
Fig. 1.3 Tapered roller bearings
α : Nominal contact angle
E : nominal small end diameter of outer ring
Fig. 1.3
Tapered
α : Nominal
contact
angle roller bearings
Single direction thrust ball
bearing
Configuration
Type
Configuration
Fig. 1.3 Tapered roller bearings
Needle roller thrust bearing
AXK type
Needle
roller thrust bearing
AS type raceway washer
AXK type
GS/WS type
raceway
washer washer
ASAXK
typetype
raceway
Configuration
2α
Sub-unit dimensions
Cylindrical roller thrust bearing
Spherical roller thrust bearing
AS type raceway washer
GS/WS type raceway washer
Cylindrical roller thrust bearing
Spherical roller thrust bearing
GS/WS type raceway washer
Cylindrical roller thrust bearing
Spherical roller thrust bearing
Center alignment
angle
A-10
Center alignment
angle
A-10
A-10
Center alignment
angle
●Classification and Characteristics of Rolling Bearings
Needle roller bearings
Bearing unit
Needle roller bearings use needle rollers as rolling
Needle
roller
bearings
elements. The needle
rollers are
a maximum
of 5 mm in
diameter
and
are
3
to
10
times
as
long
as
they
in
Needle roller bearings use needle rollersare
as rolling
Needle
roller bearings
diameter.
Because
the
bearings
use
needle
rollers
as
elements.
The
needleuse
rollers
arerollers
a maximum
ofelements.
5 mm in
Needle
roller
bearings
needle
as rolling
rollingdiameter
elements, the
cross-section
thin, butasthey
have
a
are
3 toa 10
timesisas
are in
The needleand
rollers
are
maximum
of long
5 mm in they
diameter
and
high are
load
capacity
for
their
size.
Because
of
the
large
diameter.
Because
the
bearings
use
needle
rollers
as
3 to 10 times as long as they are in diameter. Because the
number
of rolling
elements,
theasbearings
rigidity
rolling
elements,
therollers
cross-section
ishave
thin, high
butthe
they
have a
bearings
use needle
rolling elements,
crossand are
ideally
suited
to
wobbling
or
pivoting
motion.
high load
capacity
for their
of thefor
large
section
is thin,
but they
have size.
a highBecause
load capacity
their
size.
Because
of the
large number
of rolling have
elements,
number
of rolling
elements,
the bearings
highthe
rigidity
There
a profusion
of
types
of needle
bearings,
bearings
have high
rigidity
and
are ideally
suited
to wobbling
andisare
ideally
suited
to wobbling
or roller
pivoting
motion.
and just
a few ofmotion.
the most representative types are
or pivoting
covered
here.isFor
details, see
the catalog
devoted
the
There
a profusion
of types
of needle
roller to
bearings,
There
is
aaprofusion
ofmost
typesrepresentative
of needle roller types
bearings,
concerned
type
of bearing.
and just
few
of the
are and
just a few of the most representative types are covered here.
covered here. For details, see the catalog devoted to the
For details, see the catalog devoted to the concerned type of
type
bearing.
Tableconcerned
1.9 Main types
of of
needle
roller bearings
bearing.
Type
Needle roller bearing with cage
Table 1.9 Main types of needle roller bearings
Type
A unit comprised of a ball bearing inserted into various
Bearing
unit
types of housings. The housing
can be
bolted onto
machinery
and
the
inner
ring
can
be
easily
mounted
A unit comprised of a ball bearing inserted
intoon
various
Bearing
unit
the
shaft
with
a
set
screw.
types
of
housings.
The
housing
can
be
bolted
onto
A unit comprised of a ball bearing inserted into various types
This
means the
bearing
unitring
cancan
support
rotating
machinery
the inner
be easily
mounted on
of housings.
Theand
housing
can be
bolted onto
machinery
equipment
without
special
design
to
allow
for
mounting.
A
the
shaft
with
a
set
screw.
and the inner ring can be easily mounted on the shaft with a
variety
of standardized
housing
shapes
issupport
available,
This
means
thethe
bearing
unit
can
rotating
set screw.
This
means
bearing
unit
cansupport
rotating
including
pillow
and
flange
types.
outer
diameter
of
equipment
without
special
design
tofor
allow
for mounting.
A
equipment
without
special
design
toThe
allow
mounting.
A
the
bearing
is
spherical
just
like
the
inner
diameter
of
the
variety
of standardized
housing
shapesshapes
is available,
including
variety
of standardized
housing
is available,
housing,
it capable
of
aligning
itself The
onof
the
pillowincluding
andso
flange
types.
The
outertypes.
diameter
theshaft.
bearing
pillow
and
flange
outer
diameter of
lubrication,
grease
is
sealed
inside
the
bearing,
is For
spherical
just
like
the
inner
diameter
of
the
housing,
so and
the bearing is spherical just like the inner diameter
of the
it capable
of aligning
onofthe
shaft.
For
lubrication,
particle
generation
isitself
prevented
by a double
seal.
housing,
so it capable
aligning
itself
on
the For
shaft.
grease For
issee
sealed
inside the
bearing,
details,
the catalog
devoted
toand
theparticle
concerned
type of and
lubrication,
grease
is sealed
inside generation
the bearing,
is
prevented
by
a
double
seal.
For
details,
see the catalog
bearing.
particle generation is prevented by a double seal. For
devoted to the concerned type of bearing.
details, see the catalog devoted to the concerned type of
bearing.
Needle roller bearing with cage
Grease fitting
Ball
Housing
Ball
Solid type needle roller bearings
Grease
Spherical outer
ring fitting
Housing
Slinger
Spherical outer ring
Special rubber seal
Solid type needle roller bearings
Slinger
Configuration
Configuration
Special rubber seal
Setscrew with ball
Shell type needle roller bearings
Setscrew with ball
Shell type needle roller bearings
Fig. 1.4 Oil-lubricated bearing unit
Roller follower
Fig. 1.4 Oil-lubricated bearing unit
Cam follower
Roller follower
Cam follower
A-11
A-11
●Bearing Internal Clearance and Preload
8. Bearing Internal Clearance and Preload
Bearing
Internal Clearance
and Preload
Criteria
forCriteria
selecting
bearingbearing
internal
clearance
●Bearing
Internal
Clearance and Preload
8.2.1
for selecting
internal
clearance
8.1 Bearing internal clearance
A bearing’s
life is theoretically
maximum
when
A bearing's
life is theoretically
maximum
whenoperating
operating
clearance
is slightly
negativeoperation.
at steady In reality
internal clearance is the amount of internal free clearance
Bearing internalBearing
clearance
is slightly
negative
at steady
operation.
In reality
is however difficult
to constantly
movement
before
mounting.
Bearing8.internal
clearance
is the
amount of internal
free
it is however
difficult
toitconstantly
maintain
this optimal
Bearing
Internal
Clearance
and Preload
maintain
thisnegative
optimal condition.
If the
negativeenlarged
clearance by
movement before mounting.
condition.
If the
clearance
becomes
becomes enlarged by fluctuating operating conditions,
As shown in Fig. 8.1, when either the inner ring or the
fluctuating operating conditions, heat will be produced and
will be produced
life will
decrease dramatically.
outer ring is fixed and the other ring is free to move, 8.2.1 Criteriaheat
selecting
bearingand
internal
clearance
As shown
Fig.
8.1,
whencan
either
the inner ring or the outer
life will for
decrease
dramatically.
Under
ordinary circumstances
8.1 inBearing
internal
clearance
ordinary circumstances
you should therefore
displacement
take place in either an axial or radial A bearing'sUnder
life is theoretically
maximum when
ring is fixed
and
the
other
ring
is
free
to
move,
displacement
you
should
therefore
select
an
initial
internal
clearance
select an
initial internal
This amount
displacement
(radially
operating clearance
is slightly
negativeclearance
at steady where the operating
Bearingdirection.
internal clearance
is theofamount
of internal
free or axially)
can take
placeisin
either
aninternal
axial or
radial direction.
This on the
where
the operating
clearance
is slightly
larger than zero. For
is slightly
larger to
than
zero.
termed
the
clearance
and, depending
operation.
In clearance
reality
it is however
difficult
constantly
movement
before
mounting.
amount of displacement
(radially
axially)
is termed
the
ordinary
operating
conditions,
useclearance
fitting
ordinary
loads.
this optimal
condition.
If the negative
For
ordinary
operating
conditions,
usefor
fitting
for
direction, is called
the or
radial
internal
clearance
or themaintain
enlarged
by
fluctuating
operating
conditions,
shown
in Fig.
8.1,
when
eitheron
thethe
inner
ring or theis called becomes
ordinary
loads.
If rotational
speed
and operating
axial
internal
clearance.
internal As
clearance
and,
depending
direction,
If rotational
speed
and
operating
temperature
are ordinary,
be produced
and life
will
decrease
dramatically.
outer
ring is fixed
and the other
ring
is free
to move,
temperature
are
ordinary,
selecting
normal
clearance
the radial
internal
clearance
or the
axial
internal
clearance. heat will
selecting
normal
clearance
enables
you
to obtain
the proper
Under
ordinary
circumstances
you should
therefore
displacement
canthe
take
place in
either an of
axial
or radialis measured,
enables
you to obtain
the8.2
proper
operating
clearance.
When
internal
clearance
a bearing
a operating
clearance.
Table
gives
examples
applying
internal
where the
operating
direction. slight
This amount
of displacement
(radiallytoorthe
axially)
Table
8.2 clearance
gives examples
applying
internal clearances
measurement
load is applied
raceway so select
the an initial
When the
internal
clearance
ofmay
a bearing
is measured,
a slight
internal
clearances
other
CN (normal) clearance.
clearance
is slightly
larger
zero.than
is termed
the internal
clearance
and,
depending
on the
other than
CNthan
(normal)
clearance.
internal
clearance
be measured
accurately.
For
ordinary
operating
conditions,
use
fitting
for
direction, However,
is called
the
radial
internal
clearance
or
the
measurement
load
is applied
to
the
raceway
so
the
internal
at this time, a slight amount of elastic
ordinary
loads.
If rotational
speedofand
operatingclearance
axialmay
internal
clearance
beclearance.
measured
However,
atmeasurement
this
Calculation
of operating
clearance
8.2.2
Calculation
operating
deformation
of theaccurately.
bearing occurs
under the
temperature are ordinary, selecting normal clearance
time, a slight amount
elastic
clearance
of a bearing
cancan
be be
calculated
Operating
clearance
of a bearing
calculatedfrom
load, andofthe
clearance measurement value (measured Operating
enables you to obtain the proper operating clearance.
When the internal clearance of a bearing is measured, a
from initial
bearingclearance
internal clearance
and decrease
in
is slightly
larger thanthe
the measurement
true clearance. This initial bearing
deformation
ofclearance)
the bearing
occurs
internal
and decrease
in internal
Table 8.2 gives examples
applying internal clearances
slight measurement
load is
appliedunder
to the raceway
so the
internal
clearance
due to interference
and decrease
in
difference
between
the true bearing
clearance and theother clearance
load, and
theclearance
clearance
measurement
value (measured
due
to
interference
and decrease
in internal
than CN (normal)
clearance.
internal
may
be measured accurately.
internal
clearance
due
to
difference
in
temperature
of
theand
increased
amount
due
to
the
elastic
deformation
must
be
However,
at this time,
a slight
of elastic
clearance)
is slightly
larger
thanamount
the true
clearance. This
clearance due to difference in temperature of the inner
inner and outer rings.
compensated
for.occurs
Theseunder
compensation
values are given
in Calculation
8.2.2
deformation
of the
the measurement
difference
between
thebearing
true bearing
clearance
and the
outer rings.of operating clearance
8.1. Formeasurement
roller bearings
the (measured
amount of elastic
Operating clearance of a bearing can be calculated
load, andTable
the clearance
value
increased
amount
due tocan
thebe
elastic
deformation
must be
deformation
ignored.
δeff ＝δ
o −（δand
f ＋δ
t ）…………………（8.1）
from initial bearing internal
clearance
decrease
in
clearance)
is slightly larger
than
the true clearance. This
compensated
These
values
where,
internal clearance
due to interference and decrease in
differencefor.
between
thecompensation
true bearing clearance
andare
thegiven
in Tableincreased
8.1. For
roller
bearings
the values
amount
elastic
The
internal
clearance
for of
each
bearing
are
δeff
Effective internal
clearance,
clearance due
to:difference
in temperature
of themm
amount
due
to
the elastic
deformation
must
be classinternal
shown
inThese
Tables
8.3 throughvalues
8.11. are given in
δo : Bearing internal clearance, mm
inner and outer rings.
compensated
for.ignored.
compensation
deformation
can
be
Table 8.1. For roller bearings the amount of elastic
δf : Reduced amount of clearance due to
8.2canInternal
clearance selection
δeff ＝δo −（δf ＋δt ）…………………（8.1）
deformation
be ignored.
The internal
clearance
values for each bearing class are
The internal clearance of a bearing under operating where,
Table 8.1 Adjustment of radial internal clearance based on
shown The
in Tables
8.3
through
8.11.
internal
clearance
values
for
each bearing
class smaller
are
clearance,
mm
measured
load (deep
groove ball bearing)
conditions
(effective
clearance)
is usually
than the δeff : Effective internal
Unitμm
shown in same
Tablesbearing's
8.3 through
8.11.
initial
clearance before being installed and δo : Bearing internal clearance, mm
Nominal Bore Diameter
clearance adjustment
amount Measuring
of clearance
dueInternal
to
Internal clearance
selection
Load
operated.
This is due to several factors including bearing δf : Reduced
d mm
8.2
Internal clearance selection
N｛kgf｝
fit, the difference in temperature between the inner and
C2
CN
over
incl.
The internal clearance of a bearing under operating
Table 8.1 Adjustment
of radial internal clearance based on
1
outer rings,
As a bearing's
The internal
clearance
ofetc.
a bearing
under operating
operatingclearance has
10 load (deep
18 groove
24.5ball｛2.5｝
4
measured
bearing) 3∼4 Unitμm
conditions (effective clearance) is usually smaller than the
an effect
on bearing is
life,
heat generation,
vibration,
noise,
conditions
clearance)
usually
smaller
than
18
50
49
｛5｝ 4∼5
5
same(effective
bearing's initial
clearance before
being
installed
and the
Nominal
Bore
Diameter
Internal ｛15｝
clearance 6∼8
adjustment
etc.;
careclearance
must be taken
in selectinginstalled
the most suitable
50Measuring
200
8
Load 147
same bearing’s
initial
before
operated. This
is due to several
factorsbeing
including bearing and
d mm
operating
clearance. between the inner and
1 This N｛kgf｝
diameter is included in the group.
fit, the difference
in temperature
C3
C4
C5
4
6
9
4
6
9
4
6
9
operated. This is due to several factors including bearing fit, over
C2
CN C3
C4 C5
incl.
outer rings,
As a bearing's
operating
has outer
10 1
18
24.5 ｛2.5｝ 3∼4
4
4
4
4
the difference
in etc.
temperature
between
theclearance
inner and
an effect on bearing life, heat generation, vibration, noise,
Table49
8.2 Examples
of applications
clearances
50
｛5｝ 4∼5
5
6 where
6 bearing
6
rings, etc.
As a bearing’s operating clearance has an effect on18
other
than
CN
(normal)
clearance
are
etc.; care must be taken in selecting the most suitable
50
200 147
｛15｝ 6∼8
8
9
9
9 used
δ
bearingoperating
life, heat
generation, vibration, noise, etc.; care must
clearance.
1 This diameter is Operating
included in the
group.
conditions
Applications
Selected clearance
be taken in selecting the most δsuitable operating clearance.
2
With heavy or shock
δ2
Railway vehicle traction
Paper making
C4 machines
With indeterminate load, motors
Shaft or inner ring is
and driers
both inner and outer
heated.
rings are tight-fitted.
Tractors and finalRolling
speed mill table rollers
C4
regulators
δ1
ReductionPaper
of noise
and
making machines
vibration
when
rotating. Micromotors
C3，C4
Shaft or inner ring
is
and driers
heated.
Radial clearance =δ Axial clearance =δ1＋δ2
Fig. 8.1 Internal clearance
C2，CM
Adjustment of clearance
to minimize shaft runout.
(Double-row cylindrical roller
bearings)
C9NA，
C0NA
Compressor roll neck
C2
Compressor roll neck
inner and outer
rings.
Main spindles of lathes
Radial clearance =δ Axial clearance =δ1＋δ2
Loose fitting for both
A-58
inner and
outer rings.
Fig. 8.1 Internal clearance
A-58
C4
C4
C3，C4
C3
C2，CM
Main spindles of lathes
Adjustment
of clearance
C3
Rolling
mill table (Double-row
rollers
cylindrical roller
to minimize shaft runout. bearings)
Reduction of noise and
Micromotors
Loose fitting
for both
vibration when rotating.
C3
C3，C4
Railway vehicle traction
Operating conditions
Applications
With indeterminate
load, motors Selected clearance
both inner Railway
and outer
C3
vehicle
axles
With heavy or shock
rings are tight-fitted.
final speed
load, clearance is large. Vibration screensTractors and
regulators C3，C4
δ1
δ
Railway vehicle axles
Table 8.2 Examples
applications
where bearing clearances
load, of
clearance
is large.
Vibration
screens
other than CN (normal) clearance
are used
C9NA，
C0NA
C2
Courtesy of NTN Bearing
Bearing
Failure and Analysis
Bearing Failure and Analysis
Bearing
Failure are
andprecision
Analysismachine elements found in a
Rolling bearings
Rolling
bearings
are precisionThey
machine
elements
foundeven
in a
wide
variety
of applications.
are typically
reliable
wide variety
of applications.
They
are typically
reliable even
under
the toughest
conditions.
Under
normal operating
under the toughest
Under normal
operating
conditions,
bearingsconditions.
have a substantial
service
life, which is
conditions,as
bearings
a substantial
service
life, number
which isof
expressed
either ahave
period
of time or as
the total
expressed
as either
period
of time or as
theand
total
number
rotations before
the a
rolling
elements
inner
outer
ring of
rotations
thethan
rolling
elements
or inner
andspecifically—
outer ring
fatigue
orbefore
fail. Less
1 percent
(0.35
percent
fatigue
or fail.
Less
than
1 percent
percent
specifically—
see Figure
1) of
rolling
bearings
do (0.35
not reach
their
expected
see (Source:
Figure 1) FAG
of rolling
bearings
do not reach
their 1979.)
expected
life.
Bearing
Antriebtechnik
18 from
life.
(Source:Bearing
FAG Bearing
Antriebtechnik 18 from 1979.)
Premature
Failure
Premature Bearing Failure
When a bearing does fail prematurely, it is usually due to
When a that
bearing
does
failbeen
prematurely,
is usually
due to
causes
could
have
avoided. itFor
this reason,
the
causes thatofcould
haveconclusions
been avoided.
Forthe
thiscause
reason,
possibility
reaching
about
of athe
possibility
of reaching
conclusions
about theiscause
of Ita is
defect by means
of studying
its appearance
useful.
defectimportant
by meanstoofcorrect
studying
appearance
is useful.
It is
most
theits
causes
and prevent
future
most
important
correct
causes
prevent
futuresuch
failures
and the to
costs
that the
follow.
Mostand
bearing
failures
failures
and
thepitting,
costs that
follow.
Most bearing
failuresrust
such
as
flaking
and
spalling,
unusual
wear patterns,
as flaking
and pitting,
spalling,
unusual
wear patterns,
rust
and
corrosion,
creeping,
skewing
and others
are usually
and corrosion,
creeping,small
skewing
andofothers
usually
attributed
to a relatively
group
causesare
that
are
attributed
to a relatively
small group
of causes
that
are
often
interrelated
and correctable.
These
causes
include
often
interrelated
and correctable.
These and
causes
include
lubrication,
mounting,
operational stress
bearing
lubrication,
mounting,
operational
stress and bearing
selection
and
environmental
influence.
selection and environmental influence.
Proper/Improper Lubrication and
Proper/Improper
Lubrication and
“Grease Service Life”
“Grease
Service
Life”
The
purpose
of lubricating
the bearing is to cover the rolling
The purpose
of lubricating
the
bearing
cover
the rolling
and
sliding contact
surfaces
with
a thinisoiltofilm
to avoid
direct
and sliding
contact
surfaces
a thin
oil film it:
to avoid direct
metal
to metal
contact.
Whenwith
done
effectively
metal
to metal
contact.
done effectively it:
1.
Reduces
friction
and When
abrasion
1.
and abrasion
2. Reduces
Transportsfriction
heat generated
by friction
2. Prolongs
Transportsservice
heat generated
by friction
3.
life
3.
service
4. Prolongs
Prevents rust
andlife
corrosion
4. Excludes
Prevents rust
andobjects
corrosion
5.
foreign
and contamination from rolling
5.
Excludes foreign objects and contamination from rolling
elements
elements
Grease
is generally used for lubricating bearings because
Grease
generally
usedsimplifies
for lubricating
bearings
because
it
is easyisto
handle and
the sealing
system,
while
it islubrication
easy to handle
and simplifies
system,
while
oil
is generally
suitablethe
for sealing
high speed
or high
oil lubricationoperations.
is generally suitable for high speed or high
temperature
temperature
operations.
Generally lubrication
failures occur due to:
Generally
lubrication
failures
1.
The wrong
lubricant
type occur due to:
1.
wrong
lubricant type
2. The
Too little
grease/oil
2. Too much
little grease/oil
3.
grease/oil
3.
much
grease/oil
4. Too
Mixing
of grease/oil
4. Contamination
Mixing of grease/oil
5.
of the grease/oil by objects or water
5. Contamination of the grease/oil by objects or water
In addition to considering normal bearing service life, normal
In addition
to considering
normal
life, normal
grease
service
life is important
to bearing
considerservice
since together
grease
service bearing
life is important
to consider
since
together
they maximize
life. Grease
service life
is the
time
they maximize
bearing
life. Grease
service
life is the
during
which proper
bearing
function
is sustained
bytime
a
during
which
proper
bearing
function
is sustained
by a
particular
quantity
and
category
of grease.
This is especially
particular
quantity
and category
of grease.
Thisprecision
is especially
critical
in pump,
compressor,
motor
and super
critical in pump, compressor, motor and super precision
applications.
applications.
Mounting
and Installation of Bearings
Mounting
Installation
of Bearings
It
is criticaland
in the
mounting and
installation process to pay
It
is critical
in the
strict
attention
to:mounting and installation process to pay
strict
to:tools and ovens/induction heaters. Use a
1.
Useattention
of proper
1.
Use to
of impact
proper tools
and ovens/induction
sleeve
the entire
inner ring face ofheaters.
the ringUse
that ais
sleevepress
to impact
being
fit. the entire inner ring face of the ring that is
being
press
2.
Verify
the fit.
shaft and housing tolerances.
2.the
Verify
the
shaft
and
tolerances.
If
fit is
too
tight,
toohousing
much preload
is created. If the fit is
If the
fit is too tight,
too much
preload
is created.
the fittois
too
loose,
little resulting
preload
may
allow theIf shaft
too
loose,
too little
resulting
preload
allow the
shaft to
rotate
or creep
in the
bearing.
Checkmay
for proper
diameters,
rotate or creep
the bearing.
roundness
and in
chamfer
radius.Check for proper diameters,
roundness
and chamferorradius.
3. Avoid misalignment
shaft deflection. This is especially
3. Avoidinmisalignment
or shaft
deflection.
This is especially
critical
mounting bearings
that
have separable
components
critical
mounting roller
bearings
that have
separable
components
such asincylindrical
bearings
where
successful
load
such as and
cylindrical
bearings
whereor
successful
load
bearing
optimalroller
life are
established
diminished
at
bearing and optimal life are established or diminished at
installation.
installation.
4.
Be aware of radial internal clearance (see Figure 2). It is
4. Be aware
of radial
(see Figure
It is
critical
to maintain
theinternal
properclearance
RIC established
in the2).original
critical
maintain
thescale
proper
in the
originalis
design.to
The
standard
in RIC
orderestablished
of ascending
clearance
design.
scale
in order
of ascending
C2,
C0, The
C3, standard
C4, C5. The
proper
clearance
for the clearance
applicationis
C2,
C0, C3,
C4, itC5.
The proper
clearance for
is critical
in that
allows
for the challenges
of:the application
is critical in that it allows for the challenges of:
• Lubrication. A proper film of lubricant must be established
• Lubrication.
A proper
film of Reducing
lubricant must
be clearance
established
between
the rolling
elements.
internal
between
the rolling
elements.
Reducing
internal clearance
and impeding
lubricant
flow can
lead to premature
failure.
impeding
lubricantinflow
lead
to premature
failure.
•and
Shaft
fit. A reduction
thecan
radial
internal
clearance
is
•inevitable
Shaft fit.when
A reduction
in theisradial
clearance is
the bearing
pressinternal
fit.
bearing
is press fit.
•inevitable
Heat. In when
normalthe
bearing
operation,
heat is produced that
• Heat. In
normalexpansion
bearing operation,
heat
is outer
produced
creates
thermal
of the inner
and
rings.that
This
creates
thermal
expansion
of the inner
and
rings.
can
reduce
the internal
clearance,
which
willouter
reduce
theThis
can reduce
the internal
clearance, which will reduce the
optimal
bearing
life.
optimal bearing life.
Operational Stress and Bearing Selection
It is generally the exception to find a bearing that has been
improperly designed into an application. However, factors
within the larger application may change. If loads become too
high, overloading and early fatigue may follow. If they are too
low, skidding and improper loading of the rolling elements
occur. Early failure will follow in each situation. Similar issues
arise with improper internal clearance. The first sign of these
issues will be unusual noises and/or increased temperatures.
• Increased temperature. Bearing temperature generally rises
with start-up and stabilizes at a temperature slightly lower
than at start-up (normally 10 to 40 deg C higher than room
temperature). A desirable bearing temperature is below 100
deg C.
• Noises. Abnormal bearing sounds typically indicate certain
issues in the bearing application. While this is a subjective
test, it is helpful to know that a screech or howl sound
generally indicates too large an internal clearance or poor
lubrication on a cylindrical roller bearing while a crunching
felt when the shaft is rotated by hand usually indicates
contamination of the raceways. See www.pump-zone.com
for a table of abnormal bearing sounds.
Operational stresses in the applications can impact bearing
life as well. It is critical to isolate vibrations in associated
equipment as they can cause uneven running and unusual
noises.
In conclusion, the first step in the overall prevention
of bearing failure lies in the consideration of bearing
technologies most suitable to the application with regard to
specifications, recommendations, maintenance strategies,
fatigue life and wear resistance of the bearing in relation to
the application. That being said, premature bearing failure
within a proper application is typically attributed to one
or more of the causes discussed (lubrication, mounting,
operational stress and bearing selection or environmental
influence) and can and should be corrected to avoid future
bearing failures and additional cost.
P&S
Sources
• Barden Corporation. Machine Tool Technical Bulletin for
Engineering and Lubrication. 2010.
• FAG Bearings Corp. Rolling Bearing Damage. Publ. No. WL
82 102/2 December 1997.
• Fersa Bearings. Roller Bearings: Failure Diagnosis. 2009.
• Koyo Bearing Corp. Rolling Bearings: Failures, Causes and
Countermeasures. Catalog No. 322E. December 1995.
• NTN Bearing Corp. Products and Technology. Care and
Maintenance of Bearings. 2009.
Figure 2. Radial internal clearance.
Environmental Influence
Even with the best design, lubrication and installation failures
will occur if the operating environment is not considered.
While many potential issues exist, the primary ones are:
1. Dust and dirt that can aggressively contaminate a bearing.
Great care should be given to use proper sealing
techniques.
2. Aggressive media or water. Once again, sealing is primary.
The use of specialty type seals is recommended such as
pump mechanical or labyrinth style seals that do not score
the shaft.
3. External heat. The ambient operating temperature
mandates many choices in radial internal clearance, high
temperature lubricants, intermittent or continuous running
and others that affect bearing life.
4. Current passage or electrolytic corrosion. If current is
allowed to flow through the rolling elements, sparks can
create pitting or fluting on the bearing surfaces. This should
be corrected by creating a bypass circuit for the current or
through the use of insulation on or within the bearing. This
should be an inherent design consideration in applications
such as wind turbines and all power generating equipment.
Courtesy of NTN Bearing
●Bearing Damage and Corrective Measures
16. Bearing Damage and Corrective Measures
Bearing Damage and Corrective Measures
and surrounding
structure.
If handled correctly,
can generally
be used
If handled correctly,
bearingsbearings
can generally
be used
for a for
long timeconditions
before reaching
their fatigue
life.By
If investigating
damage occurs
several possible causes surmised from the type of
a long time before reaching their fatigue life. If damage
prematurely, the problem could stem from improper bearing selection, handling or lubrication. In this occurs, take note of the
damage and condition at the time the damage occurred, it
occurs prematurely, the problem could stem from
type of machine
whichselection,
the bearings
is used,
the place
where it is
is possible
mounted,
servicethe
conditions
surrounding
to prevent
same kindand
of damage
from structure.
improperon
bearing
handling
or lubrication.
In this
By investigating
several
possible
causes
surmised
from
the
type
of
damage
and
condition
at
the
time
the
damage
occurred,
reoccurring. Table 16.1 gives the main causes of bearing
occurs, take note of the type of machine on which the
it is possible
to prevent
kind of
damage
from
reoccurring.
Table 16.1
gives the
causes
bearing damage and
damage
and remedies
formain
correcting
the of
problem.
bearings
is used,the
thesame
place where
it is
mounted,
service
remedies for correcting the problem.
Table 16.1 Bearing damage, main causes of bearing damage and remedies for correcting the problem
Description
¡Riview lubricant type and quantity.
¡Check for proper clearance.
(Increase clearances.)
¡Take steps to prevent misalignment.
¡Review application conditions.
¡Improve assembly method and
handling.
Causes
¡Excessive shock loads.
¡Improper handling (use of steel hammer,
cutting by large particles of foreign matter)
¡Formation of decomposed surface
layer due to improper lubrication
¡Excessive interference.
¡Large flaking.
¡Friction cracking.
¡Imprecision of mounting mate
(oversized fillet radius)
Correction
A-96
¡Insufficient clearance (including
clearances made smaller by local
deformation).
¡Insufficient lubrication or improper
lubricant.
¡Excessive loads (excessive preload).
¡Skewed rollers.
¡Reduction in hardness due to
abnormal temperature rise
Correction
Localized flaking occurs.
Little cracks or notches appear.
¡Select a different type of bearing.
¡Reevaluate the clearance.
¡Improve the precision of the shaft and
housing.
¡Review application conditions.
¡Improve assembly method and
handling.
¡Reevaluate the layout (design) of the
area around the bearing.
¡Review lubricant type and lubrication methods.
Causes
Cracking and
notching
The bearing heats up and becomes discolored.
Eventually the bearing will seize up.
¡Excessive load, fatigue life, improper
handling
¡Improper mounting.
¡Improper precision in the shaft or housing.
¡Insufficient clearance.
¡Contamination.
¡Rust.
¡Improper lubrication
¡Drop in hardness due to abnormally
high temperatures.
Correction
Seizure
Surface of the raceway and rolling elements peels away in flakes
Conspicuous hills and valleys form soon afterward.
Causes
Flaking
¡Review lubricant (friction crack
prevention).
¡Select proper interference and review
materials.
¡Review service conditions.
¡Improve assembly procedures and
take more care in handling.
●Bearing Damage and Corrective Measures
Table 16.1 Bearing damage, main causes of bearing damage and remedies for correcting the problem
Description
¡Shaft or housing of insufficient
accuracy.
¡Improper installation.
¡Insufficient shaft or housing rigidity.
¡Shaft whirling caused by excessive
internal bearing clearances.
Correction
¡Reinspect bearing’s internal
clearances.
¡Review accuracy of shaft and housing
finish.
¡Review rigidity of shaft and housing.
Causes
¡Inadequate lubrication.
¡Entrapped foreign particles.
¡Roller skewing due to a misaligned
bearing.
¡Bare spots in the collar oil film due to
large axial loading.
¡Surface roughness.
¡Excessive slippage of the rolling
elements.
Correction
¡Reevaluation of the lubricant type and
lubrication method.
¡Bolster sealing performance.
¡Review preload.
¡Review service conditions.
¡Improve assembly method and
handling
Causes
¡Poor storage conditions.
¡Poor packaging.
¡Insufficient rust inhibitor.
¡Penetration by water, acid, etc.
¡Handling with bare hands.
Correction
Rust and corrosion
¡Reevaluation of lubrication conditions.
¡Review of cage type selection.
¡Investigate shaft and housing rigidity.
¡Review service conditions.
¡Improve assembly method and
handling.
Causes
Smearing and
scuffing
¡Excessive moment loading.
¡High speed or excessive speed
fluctuations.
¡Inadequate lubrication.
¡Impact with foreign objects.
¡Excessive vibration.
¡Improper mounting. (Mounted
misaligned)
Correction
Rolling path
skewing
Causes
Cage damage
¡Take measures to prevent rusting
while in storage.
¡Periodically inspect the lubricating oil.
¡Improve sealing performance.
¡Improve assembly method and
handling.
Rivets break or become loose resulting in cage damage.
Abrasion or an irregular, rolling path skewing left by rolling
elements along raceway surfaces.
The surface becomes rough and some small deposits form.
Scuffing generally refers to roughness on the race collar and the
ends of the rollers.
The surface becomes either partially or fully rusted, and occasionally
rust even occurs along the rolling element pitch lines.
A-97
●Bearing Damage and Corrective Measures
Table 16.1 Bearing damage, main causes of bearing damage and remedies for correcting the problem
Description
¡Electric current flowing through the
rollers.
Correction
¡Create a bypass circuit for the current.
¡Insulate the bearing.
Causes
¡Entrapment of foreign objects.
¡Bite-in on the flaked-off side.
¡Dropping or other mechanical shocks
due to careless handling.
¡Assembled misaligned.
Correction
A-98
¡Review lubricant type and lubrication
methods.
¡Improve sealing performance.
¡Take steps to prevent misalignment.
Causes
Scoring during assembly, gouges due to hard foreign objects, and
surface denting due to mechanical shock.
¡Entrapment of foreign particles in the
lubricant.
¡Inadequate lubrication.
¡Skewed rollers.
Correction
Dents and
scratches
Pits form on the raceway.
The pits gradually grow into ripples.
¡Select a different kind of bearing.
¡Select a different type of lubricant.
¡Review the interference and apply a
coat of lubricant to fitting surface.
¡Pack the inner and outer rings
separately for transport.
Causes
Electrolytic
corrosion
The surfaces wear and dimensional deformation results. Wear is
often accompanied by roughness and scratches.
¡Insufficient interference.
¡Small bearing oscillation angle.
¡Insufficient lubrication.(unlubricated)
¡Fluctuating loads.
¡Vibration during transport, vibration
while stopped.
Correction
Wear
There are two types of fretting. In one, a rusty wear powder forms
on the mating surfaces. In the other, brinelling indentations form
on the raceway at the rolling element pitch.
Causes
Fretting
¡Improve handling and assembly
methods.
¡Bolster sealing performance.
(measures for preventing foreign
matter from getting in)
¡Check area surrounding bearing.
(when caused by metal fragments)
●Bearing Damage and Corrective Measures
Table 16.1 Bearing damage, main causes of bearing damage and remedies for correcting the problem
Description
¡Infiltration of bearing by foreign matter.
¡Insufficient lubrication.
Correction
¡Reevaluation of lubricant type and
lubrication method.
¡Review sealing mechanisms.
¡Examine lubrication oil purity. (filter
may be excessively dirty, etc.)
Causes
¡Infiltration of bearing by foreign matter.
¡Insufficient lubrication.
Correction
Patches of minute flaking or peeling (size, approx. 10μm).
Innumerable hair-line cracks visible though not yet peeling.
(This type of damage frequently seen on roller bearings.)
¡Reevaluate the interference.
¡Reevaluate usage conditions.
¡Review the precision of the shaft and
housing.
¡Raceway end panel scuffing
Causes
Peeling
Luster of raceway surfaces is gone; surface is matted, rough, and / or
evenly dimpled. Surface covered with minute dents.
¡Insufficient interference in the mating
section.
¡Sleeve not fastened down properly.
¡Abnormal temperature rise.
¡Excessive loads.
Correction
Speckles and
discoloration
Surface becomes mirrored by sliding of inside and outside diameter
surfaces. May by accompanied by discoloration or score.
Causes
Creeping
¡Reevaluation of lubricant type and
lubrication method.
¡Improve sealing performance. (to
prevent infiltration of foreign matter)
¡Take care to operate smoothly.
A-99
201 Brighton Avenue • Boston, MA 02134 • Ph: 800.225.4587 • Fx: 800.252.1996 • www.emersonbearing.com