INTRODUCTION TO BEARINGS AND DEFINITIONS

Bearings explained.

1. Bearings
Nizwa College of Technology

2. BEARINGS-INTRODUCTION
•Bearings are machine elements which are
used to support a rotating member called
a shaft.
•They transmit the load from a rotating
member to a stationary member known as
frame or housing.

3. Bearing Motions
Common motions permitted by bearings are:
•Axial rotation e.g. shaft rotation
•Linear motion e.g. Carriage over the
bed, drawer in the table
•spherical rotation e.g. ball and socket
joint
•Hinge motion e.g. door

4. Bearing Loads
• Radial Load
• ThrustLoad
• Combination of both.
Fr
Radial load Thrust load Radial &Thrust load

5. Bearing Loads-Radial load
The bearings that support the
shafts of motors and pulleys are
subject to a radial load.

6. Bearing Loads-Thrust load
The bearings in this stool
are subject to a thrust load

7. Bearing Loads-Combination of Radial
&Thrust load
Thebearingsinacarwheelaresubject
toboththrustandradialloads.

8. Bearing Classification
On the basis of contact they have between
the rotating and the stationary member
•Plain bearings
(Sliding contact)
•Rolling bearings
(Rolling contact)

9. Plain bearings-Sleeve Bearing
Advantages :
It takes up less space.
It has a rigid construction
It will carry loads more effectively
It is suitable for larger diameter shafts
It is cheap to manufacture and cost less.
They operate more silently.
They have good shock load capacity.
Disadvantages:
It has higher frictional resistance
It is more difficult to lubricate
There are limited choice of designs
available

10. Sliding contact-Sleeve Bearing
Solid Sleeve
Suitable to
radial load
only
Slit Sleeve
Adjustable to
compensate
wear
Split Sleeve
Suitable for
large diameters
shafts

11. Rolling Bearings
The concept behind a ball bearing is very simple:
•Things roll better than they slide
•Two surfaces can roll over each other, the
friction is greatly reduced.
•Bearings reduce friction by providing
smooth metal balls or rollers, and a
smooth inner and outer metal surface for
the balls to roll against.
•These balls or rollers "bear" the load,
allowing the device to spin smoothly.

12. Rolling Bearings
Advantages
•The rolling bearings have a lower frictional
resistance than plain bearings
•The Lubrication of rolling bearings is easier
because they can be "grease packed'
•A greater choice of roller bearing designs are
available than for plain bearings
Disadvantages
•It takes up more space than plain bearings
•The rolling bearings are not as rigid as plain
bearings
•More nosier in operation than plain bearings

13. Types of rolling Bearings
•Ball bearings,
•Roller bearings,
•Tapered roller bearings.
•Ball thrust bearings,
•Roller thrust bearings and

14. Ball bearings
Cutaway view of a ball bearing

15. Ball bearings
•In a ball bearing, the load is transmitted from the
outer race to the ball and from the ball to the
inner race
•Since the ball is a sphere,it only contacts the
inner and outer race at a very small point,
which helps it spin very smoothly
•But it also means that there is not very much
contact area holding that load, so if the bearing
is overloaded, the balls can deform and spoil the
bearing
•Less expensive and suitable for lighter loads
and applications

16. Rolling Element Bearing Parts
Bore
Outer Race
Inner Race
Ball
Cage or Separator

17. Roller bearing
•Common roller bearings use cylinders of slightly greater length
than diameter.
•Roller bearings typically have higher radial load capacity than
ball bearings, but a low axial capacity and higher friction under
axial loads.
•If the inner and outer races are misaligned, the bearing capacity
often drops quickly compared to either a ball bearing

18. Roller bearing
Advantages
•They can carry greater radial loads
•The geometric shape of the rolling element
can be varied
•They are having greater area of contact
with the race ways
Disadvantages
•Not suitable to take much thrust load
•Expensive

19. Taper Roller Bearings
•Tapered roller bearings use conical rollers that run on conical races.
•Tapered roller bearings support both radial and axial loads, and
generally
can carry higher loads than ball bearings due to greater contact area.
•Taper roller bearings are extensively used in Machine spindles and
gear boxes using helical gears
•The disadvantage of this bearing is that due to manufacturing
complexities, tapered roller bearings are usually more expensive than
ball bearings

20. Needle Bearing
A variation of the roller type of bearing is called a needle bearing, uses
cylinders with a very small diameter.
This allows the bearing to fit into tight places.
Advantages
•Smaller diameter rollers (Needles) enable larger area of contact and greater
load carrying capacity.
•Less space is occupied
Disadvantages
•More area of contact resulted in more frictional resistance to motion.

21. Ball Thrust Bearing
•Ball thrust bearings like the one shown are mostly used for
low-speed applications and cannot handle much
radial load.
•Lead screws and feed rods use this type of bearing at its
end.

22. Roller Thrust Bearing
Roller thrust bearings like the one illustrated can support large
thrust loads.
They are often found in gear sets like machine transmissions
between gears, and between the housing and the rotating shafts.
The helical gearsused in most transmissions have angled teeth
and this causes a thrust load that must be supported by this type of
bearing

23. END