1. Design of Machine Elements – I (5ME4-04)
Lecture No.- 13
Namita Soni
Assistant Professor
MED
SKIT, Jaipur
Lecture Heading: Cotter Joint
2. Instructional Objectives
At the end of this lesson, the students should be
able to understand
Cotter Joint
Application of cotter joint
Design Procedure of cotter joint
Numerical Based on cotter joint
3. COTTER JOINT
•A cotter joint is used to connect rigidly two co-axial rods or
bars which are subjected to axial tensile or compressive
forces . It is a temporary fastening.
•A cotter is a flat wedge shaped piece of rectangular cross
section and its width is tapered (either on one side or on both
sides) from one end to another for an easy adjustment.
.
Socket Cotter
Spigot
4. APPLICATIONS OF COTTER
1. Connection of the piston rod with the cross heads.
2. Joining of tail rod with piston rod of a wet air pump.
3. Foundation bolt.
4.Connecting two halves of fly wheel (cotter and dowel
arrangement).
6. CONT…
Let P = Load carried by the rods
d = Diameter of the rods
d₁ = Outside diameter of socket
d₂ = Diameter of spigot or inside diameter of socket
d₃ = Outside diameter of spigot collar
t₁ = Thickness of spigot collar
d₄ = Diameter of socket collar
c = Thickness of socket collar
7. b = Mean width of cotter
l = Length of cotter
t = Thickness of cotter
a = Distance from the end of the slot to the
end of rod
σt= Permissible tensile stress for the rods
material
τ = Permissible shear stress for the cotter material
σc= Permissible crushing stress for the cotter material
8. SPIGOT BREAKING IN
TENSION OUTSIDE THE
JOINT
SPIGOT BREAKING IN
TENSION ACROSS
SLOT
Cotter joint– modes of failure
22. It is required to design a cotter joint to connect
two steel rods of equal diameter. Each rod is
subjected to an axial tensile force of 50 kN. Design
the joint and specify its dimensions