best of knowledge

1. DEPARMENT OF DIPLOMA MECHANICAL
ENGINEERING
PRESENTATION ON
“ COTTER JOINT”
Presentation By,
Prof. Mayur S. Itankar
Session : 2017-18
BALLARPUR INSTITUTE OF TECHNOLOGY,
BALLARPUR

2. COTTERJOINT
Acotter joint is used to connect rigidly two co-axial rods or
bars which are subjected to axial tensile or compressive
forces . It is atemporaryfastening.
Acotter is aflat 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

3. APPLICATIONSOFCOTTER
• 1. Connection of the piston rod with the cross
heads
2.Joining of tail rod with piston rod of awet
air pump
3. Foundationbolt
4.Connecting two halves of flywheel (cotter
and dowel arrangement)

4. Why taper is provided to cotter
Taper is provided due to 2 reasons.
i) When cotter is driven through the slots,
it fit, fight due to wedge action. This
ensures tightness of joint in operation
and present loosening of the parts.
ii)Due to taper, it is easy to remove the
cotter joint and dismantle the joint

5. Design of Spigot and SocketCotter
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 =Thicknessof spigotcollar,
d4 =Diameter of socketcollar,
c=Thicknessof socket collar,
b =Mean width of cotter,
t =Thicknessofcotter,
l =Length ofcotter,
a =Distance from the end of the slot to the end of rod,
σt =Permissibletensile stress for the rodsmaterial,
τ =Permissible shear stress for the cottermaterial, and
σc=Permissible crushing stress for the cotter material.

9. 1. Design of rod
i)Strengthofrod considering tensile
failureisgivenP=AreaxTensilestress

10. 2. Design of spigot –end
i) Considering failure of spigot under
tension
Area Resisting=
P
d2

11. ii) Considering shearing
failure of spigot

12. iii) Considering crushing of spigot
end
Resistingarea(A)=d2xt
• P=d2xt xσc
d2

13. 3.Designofspigotcoller
consderingshearing
failureofspigot-collar

14. ii) Failure of spigotcollar in crushing

15. 4. Design of socket
i) Considering failure of socket under
tension
AreaResisting=
LoadP=

16. ii) Considering
shearing failure
of socket

17. iii) Considering failure under
crushing

18. 5. Failure of cotter inshear