Bearings are used to reduce friction between moving machine parts and support rotating components like shafts. There are two main types of bearings: plain bearings, which support sliding and rotational motion directly, and anti-friction or roller bearings, which use balls or rollers to further reduce friction. Journal bearings surround shafts at right angles and include types like open, bushed, plummer block, and pivot bearings. Cotter joints connect rods rigidly to transmit axial forces without rotation using a wedge-shaped cotter pin. Sleeve and cotter joints connect circular rods using a hollow steel sleeve and cotter pin.

1. Machine parts and machine drawings
Bearings
1. Friction is greatly reduced in moving parts by using bearings.
2. In industries bearings are used to help in smooth running of shafts.
3. Bearing is a part of a machine which support another part that turns round a wheel.
4. Bearing is a support and guide for rotating, oscillating, or sliding shaft , pivot or wheel.
5. Two types of bearings according to type of motion are plain bearings and antifriction bearings or
roller bearings.
6. Plain bearings support sliding, radial and thrust loads and linear motions.
7. Plain bearings are classified as
1. Plain Journal Bearings: These support radial loads at right angles to the shaft axis.
2. Spherical Bearings: These are used where the loads are not aligned and are radial.
3. Thrust Bearings: These bearings support axial and radial loads.
4. Linear Bearings: These bearings only help in linear motion.

2. 5. Pivot Bearings or Foot Step Bearings: These bearings are used where the thrust is
only axial.
8. Anti-friction or roller bearings are classified as
1) Needle bearings
2) Ball bearings and
3) Roller bearings
9. The bearings mentioned above can be rearranged according to the loading
conditions as:
1. Journal Bearings: In this bearing the bearing pressure is perpendicular to
the axis of the shaft.
2. Thrust Bearing or Collar Bearing: In this bearing the pressure is parallel
to the axis of the shaft.
3. Pivot Bearing: In this bearing the bearing pressure is parallel to the axis
of the shaft and the end of the shaft, rests on the bearing surface.
4. Linear Bearings
5. Spherical Bearings.
10. Journal bearing forms the sleeve around the shaft and supports a shaft at right angles
to the axis of the bearing.
11. Examples of journal bearing are
i. Open bearing
ii. Bushed bearing
iii. Plummer block or pedestal bearing
iv. Pivot bearing or footstep bearing
1. Bushed bearing is a journal bearing in which a bush made of soft material such as brass, bronze
or gun metal is used.
2.It is useful for higher loads at medium speed.
3.The brasses(bushes) are prevented from rotating or sliding by the use of grub screw or dowel-
pin inserted half inside the bush and half in the body of the bearing.
4.The bushed bearing is generally placed near the ends of the shaft, because in this the shaft can
be inserted and wise only.
5.The sole is recessed up to 3mm leaving a standing material all around, known as padding which
helps in the stability and reduces the machining area.

3. 6.Open bearing is useful for linear and zig zag shafts and shafts rotating at low speeds.
7.The plummer block is also known as pedestal bearing
8.This bearing is useful for long shafts requiring intermediate supports and are preferred over
ordinary bushed bearings.
9.It was named after its inventor ‘PLUMMER’.
10. It is used for shafts rotating at high speeds and hence needs frequent replacement of
brasses due to wear and tear.
11. The cap in the bearing rests on the upper brass , fits inside the body with its body cap at
its sides “but does not sit on it”.
12. Footstep bearing is used for supporting the lower end of the vertical shaft.
13. The drawback of this bearing is that there is no proper lubrication, thus unequal wear
and tear is there in the bottom of the round disc.
Rod joints
1. A cotter is a flat rectangular cross section wedge-shaped piece or bar of mild steel block which
is uniform in thickness but tapering in width on one side in general
2. It is used to connect rigidly two rods, whose axes are collinear and which transmit motion in th
axial direction(tensile or compressive force) without rotation.
3. Thickness of cotter(t)=0.3D
4. Length of cotter(l)=3.5D to 4D, where the average dimension of the cotter is (d)=1.3D
5. The cotter joint is a temporary fastening, which allows the assembly and disassembly of a unit
without damaging the fastened elements of the connecting components.
6. Steel is the common element used for this application
7. Applications of cotter joint are fastening of piston rods and cross heads in steam engines,
yokes in rods, tool fixtures and for services of similar kinds….
8. The joint is useful in the following conditions
(i) To connect a rod directly with a machine, so as to transmit a force to the machine
through the rod or vice- versa.
(ii) When it is desired to increase the length of the rod.
(iii) To connect two rods rigidly in the direction of their length.

4. 9. There are three cotter joints for connecting circular rods
a) Sleeve and cotter joint
b) Socket and spigot joint and
c) Knuckle joint
10. For joining square or rectangular rods gib and cotter joint is used.
11. Sleeve and cotter joint is used to connect two round rods or sometimes to connect
two pipes /tubes.
12. The ends of the two rods to be joined are chamfered to avoid burring and easy
insertion in the hollow steel sleeve
13. When sleeve and rods are subjected to axial tensile force then the cotter is
subjected to shearing force.
14. These joints are used for light transmission of axial loads.