contact : 86-13269832656 Kaiyang_000@yahoo.cn China Bearings Tires Nominated Supplier in Beijing 嘉能元国际贸易（北京）有限公司 Beijing JiaNengyuan International Trading Co., Ltd
conventional machines and equipment experience is the best guide but
in general the coefficients listed below may be applied to determine
the equivalent load used in the life calculations:
– 1.2 machinery or mechanisms operating smoothly without repeated
– 1.3 geared transmissions according to gear quality,
1.4 – 3.0 machinery or equipment operating under repeated shocks or
As far as belt drive transmissions are considered, the calculated
tangential load should be multiplied by the following coefficients:
2.0 – 2.5 for v belts,
2.5 – 5.0 for flat belts according to drive tension.
188.8.131.52 Variable loads and speeds
When the loads and speeds are variable, the life calculation can
only be made by first establishing an assumed constant load and
constant speed equivalent in their effect on the fatigue life of the
This type of operating condition is frequently met and the
possible variations although cyclical are numerous. One encounters
this feature in particular, in variable speed drives.
Lubrication of the bearing has got such a great importance, as raw material from which from
which they are made. Anticipated life of the bearing largely depends on the quality and quantity
of the lubricant and its method of application. Rare lubrication and improper lubrication of a
bearing result in the reduced bearing life and its premature failure. It is therefore, very essential
to make a proper choice of lubricant.
The advantages derived from the correct choice of lubricant are:
1. It protects the bearing from corrosion.
2. It protects the bearing to a certain extent, from the entrance of foreign matter in to the
3. It minimizes the friction between the races and rolling elements.
4. It reduces the friction arising due to elastic deformation of rolling elements when under
5. It facilities the smooth running of bearing by minimizing noise.
6. It creates the lubricant film on the raceway of the bearing and thereby protects the
raceway from blows of the rolling elements.
7. It dissipates the heat from the bearing and also helps distribute uniformly the frictional
heat throughout bearing, which is generated during operation. 1. TECHNICAL INFORMATION
1.1 BEARING HISTORY
Hundred of years ago, when man lacked strength and endurance to carry
loads, such heavy loads to be transported were put on simple skids and
dragged to the place of destination. The dragging heavy load on dry ground
requires considerable force. These forces can be reduced by using lubricants
between the sledge runners and the ground. This lubricant-probably water –
was poured to reduce the friction and thereby reducing the volume of force.
As the time passed on, these forces were further reduced when man learnt to
insert wooden rollers between the ground and the object. THUS SLIDING
MOTION WAS CONVERTED INTO ROLLING MOTION, which is the
basic principle of bearing. However, things were not much changed for
years, till the concept of BALL was conceived, as the application of rollers
was not practical everywhere. In 17th
century, stone balls were produced and
were in use for variety of applications to minimize the friction. Since the
stone balls were not suitable for many applications, cast iron balls were also
produced, but that was also not suitable. In 19th
century, the concept of steel
balls was conceived and steel balls were produced. During this era, on lathe
machines, balls of remarkable accuracy were cut off from a steel rod and the
ends were machined to form a sphere. At the end of 19th
manufactured by this method in England were within the tolerance of 0.025
to 0.050 mm. In the year 1883, Friedric Fischer, instrument maker in
Scheweinfurt – W. Germany, after numerous experiments, developed a
method of grinding wheel balls, turned between the centers on the centre less
principle. For this purpose, he designed ball grinding machine called “BALL
MILL”. In 1898 taper roller bearing unit developed in USA by H. Timken.
During 1913-1914 Roller bearings were put on use.
The choice of a bearing depends on many factors that need to be examined
in order to obtain the most successful results at the lowest cost.
In most cases the selection should be made when the overall design of the
machine has been decided. Dimensional limits are then known, as well as
the speeds and loads. At this stage the choice can be made from the many
types of bearings offered from the Galaxy Bearing Ltd. standard ranges and
the notes given in this section will generally permit selection of the most
suitable bearing for each application. When calculating the cost of the assembly, not only should the price of the bearing be considered, but also
cost for heat treatment, machining and handling and fitting of ancillary items
(snap rings, locking devices, tools etc.) and the eventual quantities required.
Large economies can be made on these items if the correct bearings are
selected. Something it is more advantageous to choose a bearing of slightly
higher cost, which will however, when all criteria are taken into
consideration, provide the most economic solution. The result obtained from
bearings depends to a large extent on the design and method of assembly,
loading, and alignment between inner and outer rings. The introduction of
‘Anti-friction’ or ‘Rolling Contact Bearing’ proved far superior to plain
Bearings because of their classic advantages, Such as
™ Low friction – particularly low starting friction.
™ Their ability to support both radial and thrust load and speed.
™ Accurate performance under changing load and speed.
™ High load carrying capacity.
™ Operating ability under extreme conditions of speed and
These bearings vary in size, from ‘tiny pin-head’ to ‘giant sized’
Bearings for Cement/Rolling Mills/Radars etc.
Bearings are so widely used that today, we find their application in
objects like the charkha, chairs, doors, filling-cabinets, children’s toys, as
well as in the most sensitive instruments like computers, data processing
machines, rockets and aerospace instruments.
1. 3 BEARING STANDARDS
Galaxy Bearing Ltd standard metric and Inch bearings conforms to
International standards (ISO) for boundary dimensions, tolerances and
internal clearances. They also comply with the associated DIN, AFBMA
AND British Standards. Galaxy Bearing Ltd has comprehensive
specifications for materials, heat treatment and quality control to ensure high
precision products made from clean bearings steels.
1. 4 MATERIAL
The process of manufacturing Bearing Steel does not start at a Bearing Plant
but at the steel mill. The SAE-52100 standard Bearing Steel contains
varying amount of carbon, iron, chromium, manganese, phosphorus,
sulphur, silicon, etc. Each of these elements plays a vital role in making the final steel suitable for Bearings. Chromium and carbon allow deep
hardening. Where as the combination of Carbon, Chromium and Iron helps
to minimize Bearing failures as they increase the surface resistance to
abrasion and wear & tear. A proper combination of all these elements make
the final Bearing Steel tough enough to withstand shocks & heavy loads and
hard enough to resist fatigue.
Generally Bearings are made from tubes or bars, but nowadays, many
Bearings manufacturers are inclined to make Bearings from forged rings.
Large-sized Bearings are manufactured from forged rings. It is filet that
Forged Bearing Rings have makes them more durable.
ROLLING ELEMENTS, CAGES SHIELD AND SEALS.
Moreover, balls characteristically minimize the friction to a greater extent
than any other rolling elements. This is why ‘Ball Bearings’ are more
versatile than any other type of Bearings. Other rolling elements used in
Bearings are Cylindrical Rollers, Taper Rollers, and Spherical Rollers,
Needle rollers, Concave Rollers and a combination of Ball & Needle etc.
Basically, every Anti-friction Bearing consists of four basic parts, an
outer ring, rolling element and a cage.
The cages are made in various designs and out of various materials,
But there are two main types of cages:-
™ Pressed Steel Cage made from Strip Steel and
™ Turning & Drilling Machine Cage made from Carbon Steel.
The cages keep rolling elements properly spaced out between two
rings. The cage may be of steel, brass, etc. depending upon the type and
application of the Bearings. Rolling elements can be balls, cylindrical
rollers, spherical rollers or taper rollers. Standard bearings are made using
high quality carbon-chrome through hardening steel of similar composition
of the following specifications: SAE 52100 OR 100Cr6
1.5 SELECTION OF BEARINGS
1. After knowing all about bearings the important thing is the proper
selection of bearing for any moving vehicle or machine.
2. The selection of ball & roller bearings for a given installation depends
upon the following factors.
The load carrying capacity & the nature of the load. The type of service under given conditions such as temperature,
humidity, dustiness, acidity, etc.
The anticipated life of the bearing.
Magnitude and direction of loads.
The proportion of thrust to radial load.
3. Cylindrical Roller Bearings are suitable for those shafts which have
been allowed to move freely longitudinally within certain limits, and
for far larger and heavily loaded applications.
Taper Roller Bearings are suitable where radial and thrust loads or
any combination of both are required to be handled and in dealing
with heavy composite loads as in case of automobile parts.
In very high speed spindles and machines only, bearings with
precision tolerances are used.
4. The capacity of the bearings decreases as the speed increases. If a
bearing operates continuously, its life expectancy measured in hours
will obviously be shorter than if operated intermittently. Some types
of bearings can carry only radial loads or thrust loads while some
types of bearings can carry both radial as well as thrust loads. So if a
bearing which can carry only thrust loads is put under radial loads, it
will either break or damage the machine into which it is fitted. So, a
proper selection is necessary. One major cause for bearing failure
depends on selection of bearings.
In short the proper selection of bearings is most essential and
will ensure the longer life of the bearings as well as the life of the
machine in which it is used.
If the bearing loads with its directions of the ratio of radial and
thrust capacity and speed is accurately determined, its life span can
also be established. The necessary bearings size can also be
determined. However the selection is so complex that general rules
can hardly be drawn up.
1.6 CALCULATION FOR RADIAL ROLLING BEARINGS
The calculations for radial rolling bearings must take account of the
following principal factors:
™ Actual supported loads and possible shock loads
™ Speed of rotation
™ Operating temperature
™ Hardness of the bearing raceways Other features such as lubrication, sealing and alignment do not enter
directly into life calculations but they must be considered in order to avoid
introducing unfavorable factors.
The life calculation of a radial bearing or a thrust bearing under
rotation is established from the dynamic capacity C indicated in the tables of
dimensions. The static capacity Co enables one to determine the maximum
load under certain conditions.
1.6.1 DYNAMIC CAPACITY C
The dynamic capacity of a bearing is the constant radial load
which it can support during 1 000 000 revolutions before the first
signs of fatigue appear on a bearing race or rolling element.
1.6.2 NOMINAL LIFE
The life of a radial bearing is the number of revolutions (or the
number of hours at constant speed) that it will maintain before
showing the first signs of material fatigue.
The relationship between the life is millions of revolutions L10,
the dynamic capacity C and the supported load P, is given by the
L10 = ( C/P )
In which :
L10 – Basic rating life (106
C – Basic dynamic load rating (Newton)
P – Equivalent dynamic load (Newton)
P – is equal to 10/3 for needle or roller bearings and 3
for ball bearings.
The formula above is independent of speed of rotation, which
must not exceed the recommended limit in respect of the radial
bearing or the thrust bearing used and the method of lubrication.
If the speed of rotation n (rpm) is constant, the life is given in
hours by the function:
L10 h = (L10 x 106
)/60 n hours
The life in hours is then inversely proportional to the speed.
The above formulae will ensure that 90% of the bearings
operating under the same conditions will attain at least the calculated
L10 life, known as the nominal life (the figure being the percentage of bearings which may not attain this life). The formulae are based on the
use of standard quality bearing steel and assume a satisfactory method
1.6.3 MODIFIEDL LIFE Lna
In various conditions modified life can be determined (in
millions of revolutions) following the general formula:
Lna = a1 a2 a3 L10
Lna = adjusted rating life, millions of revolutions
In which a1, a2 and a3 are correction factors linked to
reliability, material and lubrication respectively.
1.6.4 Reliability correction factor a1
A reliability factor in excess of 90% may be required in
certain industries, such as aviation, for reasons of security and to reduce the
risk of very costly immobilization.
The table below indicates the values of the correction
factor a1 as a function of reliability:
Reliability % Factor a1 Corrected Life
In order to select as an example a bearing of L4 life
(reliability 96%) it is necessary to consider a theoretical L10 life
(reliability 90%), equal to L4/0.53 applied in the formula L10 = (C/P)
using the dynamic capacity C given in this catalogue.
1.6.5 EQUIVALENT LOAD AND SPEEDS
184.108.40.206 Overload factors
The load on a radial or thrust bearing is established from the
characteristics of the machine together with the working loads
prevailing. However, account should also be taken as far as possible
of the supplementary loads which arises due to imperfections in
transmission, etc. or due to overloads, shocks and vibration. For 8. Power losses can be saved, as internal friction can be prevented.
9. It also helps the bearing to attain the required speed.
10. It helps to attain the anticipated life of the bearing.
There are TWO types of lubricants used for bearing lubrication. OIL and
Oil lubrication is considered to be the most efficient than Grease, provided proper sealing
methods are employed to prevent the leakage. Only highly refined OIL should be used as bearing
OIL is preferred when…
1. Bearing speed is very high.
2. Operating temperature is consistently high.
3. Sealing methods can be easily employed.
4. Bearing application demands that Grease is not suitable.
Then during operational condition, most of the lubricant will be forced out of the bearing which
can never come back into the bearing, and such lubricant is not suitable for reuse.
For many applications, grease is considered to be more convenient than oil. Grease used as
lubricant should be of smooth texture and non-fibrous. It must be free from chemically or
mechanically active ingredients. For bearing lubricants, general-purpose sodium-soap petroleum
grease is preferred. It is suitable for variety of speed and temperature conditions and has rust
preventive character under humid conditions.
For specific working conditions and operational requirements special type of Greases are used
1. Lithium soap petroleum oil grease.
2. Lithium soap di-ester grease.
3. Lithium soap silicon grease.
4. Special quality grease to withstand temperature conditions from minus 200
Generally Grease lubrication is preferred when…
1. Temperature is not excessive (Not over 200 F).
2. Speeds are moderate.
3. Extra protection from Dirt, Fumes, and other foreign matter is required.
4. Long time operations without maintenance are the requirement.
1.7.3 SELECTION OF LUBRICANT
1. For small size bearing operating at high speed, low viscosity oil is used.
2. Large bearings carrying heavy loads, lubricant with higher viscosity and additional adhesive
properties may be used. 3. For any application, the lubricant must have sufficient lubricating capacity at prevailing
4. It must from a load sustaining lubricating film for prevailing load conditions.
5. It must have the capacity to absorb water to a certain extent, without affecting the
lubricating capacity, wherever the application demands.
Thus one should ascertain the correct type of lubricant, which is suitable for operating
conditions. When the lubricant quantity is inadequate, it results in the cage failure, and
inadequate lubrication may heat up cage, may breakdown the ball pocket, and progressively
break the whole cage. Even non-metallic cage also becomes brittle, dry and crack apart under
heat and stress. Due to break down of the lubricating film on raceway and rolling element
surfaces, they may also develop scoring marks, gradually resulting in bearing failure. This
condition may also result in the deformation of parts, and when the bearing with deformed parts
rotate under load, it will have sliding motion instead of rolling motion, and it ends up in bearing
failure. Normally a medium size bearing running at the speed of 2000-6000 RPM can be
sufficient lubricated with only few drops of oil per hour.
1.8 BEARING TOLERANCES
GBL tolerances for bearings conform to values for normal class bearings to ISO
Standards. Bearings of other tolerance classes (closer tolerances) can be supplied at extra
cost provided the quantity is sufficient.
d = bearing bore diameter, nominal
d1 = basic diameter at the theoretical large end of a basically tapered bore
Δds = deviation of a single bore diameter
Δdmp = single plane mean bore diameter deviation
Δd1mp = mean bore diameter deviations at the theoretical large end of a basically
Vdp = bore diameter variation in a single radial plane
Vdmp = mean bore diameter variation
D = bearing outside diameter, nominal
D1 = outside diameter of outer ring flange
ΔDs = deviation of a single outside diameter
ΔD1s = deviation of a single outside diameter of outer ring flange.
ΔDmp = single plane mean outside diameter deviation
VDP = outside diameter variation in a single radial plane
VDMP = mean outside diameter variation
B = Inner ring width, nominal
ΔBs = deviation of a single width of inner ring
VBS = Inner ring width variation
C = outer ring width, nominal
C1 = outer ring flange width
ΔCs = deviation of a single width of outer ring
ΔC1s = deviation of a single width of outer ring flange
VCS = outer ring width variation VC1S = variation of outer ring flange width
Kia = radial run out of assembled bearing inner ring
Kea = radial run out of assembled bearing outer ring
Sd = runout of inner ring reference face (back face, where applicable) with
respect to the bore
SD = variation of outer ring outside surface generatrix inclination with
respect to the outer ring reference face (back face)
SD1 = variation of outer ring outside surface generatrix inclination with
respect to the outer ring flange back face
Sia = runout of inner ring face (back face) with respect to the raceway of
Sea = runout of outer ring face (back face) with respect to the raceway of
Sea1 = runout of outer ring flange back face with respect to the raceway of
‘α = taper angle (half the cone angle) of inner ring bore
1.8.2 ADDITIONAL SYMBOLS FOR TAPERED ROLLER BEARINGS
T = bearing width
ΔTs = deviation of the actual bearing width
T1 = effective inner subunit width
ΔT1s = deviation of the actual effective inner subunit width
T2 = effective outer subunit width
ΔT2s = deviation of the actual bearing width
1.8.3 NORMAL TOLERANCE CLASS
(Radial bearings except tapered roller bearings)
Bore diameter tolerances given in the table apply basically to cylindrical bores.
1.8.5 TOLERANCES FOR TAPERED ROLLER BEARINGS (INCH SERIES):
Tolerance values in microns
Tolerances for bore dia. and running
Tolerances for OD and running
diameter d (mm)
over Incl. high low Max. high low high low high low over incl high low Max.
– 76.200 +13 0 51 +76 -254 +51 -254 +203 0 – 304.800 +25 0 51 76.200 266.700 +25 0 51 +356 -254
1.8.6 TAPERED BORE TOLERANCES – NORMAL TOLERANCE CLASS
Basically tapered bores, tapers 1:12 and 1:30
a) For taper 1:12
The taper angle (half the cone angle) is α = 2° 23’ 9.4” = 2.385 94° = 0.041 643
The diameter at the theoretical large end of the bore is d1 = d + (1/12) B
b) For taper 1:30
The taper angle (half the cone angle) is α = 0° 57’ 17.4” = 0.954 84° = 0.016 665
The diameter at the theoretical large end of the bore is d1 = d + (1/30) B
The tolerances for a tapered bore comprise:
o A mean diameter tolerance, given by limits for the mean diameter
deviation at the theoretical small end of the bore Δdmp ;
o A taper tolerance, given by limits for the difference between the mean
diameter deviations at the two ends of the bore, Δd1mp – Δdmp ;
o A tolerance for the diameter variation, Vdp, given by a maximum value
applying in any radial plane of the bore.
Tapered bore, taper 1:12 Tolerance values in micrometers
Δd1mp – Δdmp
over Incl High low max high low
0 120 180 +40 0 31 +40 0
Tapered bore, taper 1:30 Tolerance values in micrometers
Δd1mp – Δdmp
over Incl High low max high low
1.9 CHAMFER DIMENSION LIMITS
Limit dimensions of chamfar
r1, r3 Chamfar in radial direction
r2, r4 Chamfar in axial direction
rsmin General symbol for the minimum
r1smax, r3smax maximum chamfar in radi
r2smax, r4smax maximum chamfar in axia
Cham far of radial bearings
Dim ension in m m
0,1 0,15 0,2 0,3 0,6 1 1,1 1,5 2 2,1 2,5 3 4 5 6 7,5 9,5 12 15
Nom inal over
diam eter to 40
40 50 120 120 80 220 280 280
40 50 120 120 80 100
280 280 220
r1m ax 0.2 0.3 0.5 0.6 0.8 1 1.3 1.5 1.9 2 2.5 2.3 3 3.5 3.8 4 4.5 3.8 4.5 5 5 5.5 6.5 8 10 12.5 15 18 21 25
r1m ax 0.4 0.6 0.8 1 1 2 2 3 3 3.5 4 4 5 4.5 5 6 6.5 7 6 6 7 8 8 9 10 13 17 19 24 30
Dimension in mm
0,3 0,6 2 2,5 4 6
outside diameter D
50 120 120 120 400
120 250 120 250 120 400
r3max 0.7 0.9 1.1 1.3 1.6 1.9 2.3 2.8 3.5 2.8 3.5 4 3.5 4 4.5 4 4.5 5 5.5 5 5.5 6 6.5 6.5 7.5 7.5 9
r4max 1.4 1.6 1.7 2 2.5 3 3 3.5 4 4 4.5 5 5 5.5 6 5.5 6.5 7 7.5 7 7.5 8 8.5 8 9 10 11
11,5 3 5
2. BEARING MOUNTINGS
Bearing is a precision machine member and is very sensitive to improper treatment.
Therefore, while mounting the bearing, utmost care is necessary:
1. Mounting of a bearing should be done in clean, dry, dust free room.
2. While mounting, never remove the preservative coating of thee bearing.
3. If the bearing becomes DIRTY, then clean it with suitable solvents.
4. Never wash NEW bearing with kerosene etc. before mounting.
5. Never remove bearing from its packing, till it is ready for mounting.
6. Bearing seating and other components should be thoroughly cleaned.
7. Check thoroughly dimensional and form accuracy of seating and shaft.
8. Prescribed FITS must be maintained on the shaft and housing.
9. While mounting the smaller bearing onto the shaft, transmit the force thru inner ring only
and NOT thru outer ring or thru cage.
10. While mounting the bearing in the housing, force must be transmitted through outer ring
only and not thru inner ring or the cage.
11. Never blow hammer directly on thee bearing. Instead, use a suitable size of mounting
bush thru which uniform force can be transmitted over the entire ring surface. 12. For mounting the large size bearing it is preferable to heat the bearing up to 800
While heating the bearing, make sure that accurate temperature control is maintained,
because excessive heat may cause the reduction in the hardness of the bearing.
Oil bath, Hot plate, Temperature controlled electric oven etc. are suitable means to heat the
bearing. At last see that mounting of the bearing is done by a skilled person, who has through
knowledge of the job procedures, tools, knowledge of the force to be applied etc. Any ignorance
of these factors may result in damage of the bearing and reduced service life. Experience shows
that the amount of shrinkage required for easy fitting is barely depending upon the interference
As a general rule, the following temperature value can be used.
Below 100 mm 900
From 100 mm to 150 mm 1200
Above 150 mm 1300
2.1 HOW TO PREPARE ROLLING BEARING FOR MOUNTING
2.1.1 Working Planning
Know in advance what you are going to do so that the mounting work can proceed in a
straightforward manner. Study the shop drawing to acquaint you with the design details
of the application and the assembly sequence. Phase the individual operations and get
reliable information on heating temperatures, mounting forces and the type and the
amount of greases to be packed into the bearing. Whenever the installation and removal
of rolling bearing necessitates special measures the fitter should be provided with
comprehensive instructions on mounting details, including topics such as the means of
transport for the bearing, the mounting equipment, measuring devices, heating facilities
and type and quantity of lubricant.
2.1.2 Before starting mounting
Before starting mounting the fitter should satisfy himself that bearing number stamped on
the package agrees with the designation given on the drawing and in part list. He should
therefore be familiar with the bearing numbering and identification system.
2.1.3 Handling of rolling bearings before mounting:
Before being packed, the bearings are coated with preservative oil, which prevents corrosion.
The oil does not need to be washed out when mounting the bearing. In service, the oil
combines with the bearing lubricant. Do not perform any modifications on the bearings.
Subsequent drilling of lubricating holes, machining of grooves, flats and the like will disturb the stress distributions in the ring resulting in premature bearing failure. There is also the risk
of chips or grit entering the bearing.
2.1.4 Cleanliness in mounting
An absolute “must” for the proper fitting of roller bearings is working in clean
surroundings. The tools to be used should be free from dirt & fillings. In the room where the
fittings of the bearings are carried out it is absolutely essential to avoid machining with metal
cutting tools. If, despite these precautions, bearings get dirty by improper handling, they must not
be rotated because even the smallest particles penetrating into the bearing will damage the races
and in this way the service life of the bearing will be considerably reduced.
Attention should also be given to the cleanliness of shaft, housing and any other mating
parts. Castings must be free from sand. After cleaning the housing bore should receive a
protective coating. Bearing seats on the shaft and in housing bore should be carefully cleaned
from antirust components and residual paint. Turned parts must be free from burr and sharp
2.1.5 Surrounding parts
All surrounding parts should be carefully checked for dimensional and geometrical
accuracy before starting mounting. Non-observance of the tolerances for shaft and housing seat
diameters, out of roundness of these parts, out of square of abutment shoulders etc. impair
bearing performances and lead to premature failure is not always easy to establish and much time
can be lost in looking for the cause of failure.
Good bearing performance is largely depending on adherence to the fits specified for the
two rings in the drawing. No one can give a straight answer to the questions of the “right” fit.
Indeed the selection of fits is determined by the operating conditions of the machines and the
design characteristics of the bearing mounting.
Basically, both rings should be well supported over their seating areas and should
therefore be tight fits. This, however, can not be used in all cases, since other factors, such as
axial freedom of the floating bearing or easy mounting must also be taken into consideration.
The interference produced by tight fits expends the inner ring and contracts the outer ring
resulting in a reduction of redial clearance. Hence the radial clearance should be adapted to the
fits. The shaft and housing tolerances should be checked. A too loose fit causes the ring to creep
on the shaft, which tends to damage both ring and shaft. It also affects the working accuracy of
the machine or causes premature raceway fatigue from poor support. On the other hand, to tight a
fit leads to a reduction in radial clearance, which might result in detrimental preload and hot
running of the bearing. The seating areas must, moreover, be checked for out of round in
addition to diameter. As the walls of the rolling bearings are relatively thin, possible poor
geometry of shaft or housing is transmitted to the raceways. Out of round and deviation from
true parallelism and taper should not exceed half the specified diameter tolerance. For Radial bearings with cylindrical bore of normal precision class. (Tapered &
Several factors like the type and magnitude of bearing load, temperature difference,
method of bearing mounting and dismounting should be taking into consideration while
selecting the proper fit.
The recommended tolerances for shaft and housing for common applications are given
below as general guide lines:
Type of rotation Load
Type of fitting
Inner Ring Outer Ring Inner Ring Outer Ring
Rotation Stationary Rotating inner
Tight Fit Loose Fit
Stationary Rotation Rotating inner
Tight Fit Loose Fit
Tight Fit Tight Fit
TABLE – RECOMMENDED SEATING FITS FOR SHAFTS*
Load Conditions Examples
Shaft Diameter (mm)
Shaft Tolerances Cylindrical Roller & Taper
of inner ring
Wheels on Stationary
All Shaft Diameters
of inner ring
Tension Pulleys and Rope
< 40 ‘js6 (j6)
40 ~ 140 ‘k6
140 ~ 200 ‘m6
to 0.13 C(1)
Applications, Medium &
Large Motors, Turbines,
Pumps, Engine Main
< 40 ‘k5~6
40 ~ 100 ‘m5~6
100 ~ 140 ‘m6
140 ~ 200 ‘n6
200 ~ 400 ‘p6
( >0.13 C(1)
Railway Axle boxes,
50 ~ 140 ‘n6
140 ~ 200 ‘p6
Over 200 ‘r6
Axial Loads Only All Shaft Diameters ‘js6(j6)
C represents the basic dynamic capacity of the bearing
* Applicable only to solid steel shafts
TABLE – RECOMMENDED SEATING FITS FOR HOUSING*
Load Conditions Examples
nt of Outer
Heavy Loads on
Bearing in Thin-
Impossible Normal and Heavy
Light and variable
Heavy shock loads Traction Motors
Normal and Heavy
Normal and Light
JS7 (J7) Possible
Loads of all kinds
Railway Axle boxes
nt Normal and Light
Plummer Blocks H8
rise of inner Ring
Papers Dryers G7
Normal and Light
Rear Ball Bearings,
Front Ball Bearings,
and High rigidity
Normal and Light
Machine Tool Main
M6 / N6 Impossible
Minimum Noise is
* Applicable for cast iron and steel housings. For housings made of light alloy, the
interference should be tighter than those in this table.
3. BEARING HANDLING
When handling bearings…….
1. Remove all outside dirt from housing
before exposing bearing
1. Don’t work in dirty surrounding.
2. Treat a used bearing as carefully as you
would a new one.
2. Don’t use dirty, brittle or chipped tools.
3. Work with clean tools in clean
3. Don’t use wooden mallets or work on
wooden bench tops.
4. Handle with clean, dry hands, or better, 4. Don’t handle with dirty, moist hands. clean canvas gloves.
5. Use clean solvents and flushing oils. 5. Don’t use gasoline containing
tetraethyl lead, as they may be injurious
6. Lay bearings out on clean newspaper. 6. Don’t spin uncleaned bearings.
7. Protect disassembled bearings from
rust and dirt.
7. Don’t spin bearings with compressed
8. Use clean rags to wipe bearings. 8. Don’t use cotton waste or dirty cloth to
9. Keep bearings wrapped in oil proof
paper when not in use.
9. Don’t expose bearings to rust or dirt.
10. Clean inside of housing before
10. Don’t nick or scratch bearing