This document discusses the design of a socket and spigot cotter joint. A cotter joint is used to rigidly connect two coaxial rods subjected to axial tensile or compressive forces. It consists of a tapered wedge-shaped cotter that fits into slots in the spigot and socket. The document outlines various failure modes of the joint and provides examples of sizing a cotter joint to withstand specified loads.

1. Socket and Spigot Cotter
Joint
Presented By
Mr.S.Saravanakumar,M.E.,
Assistant Professor
Easwari Engineering College
Mr.S.Saravanakumar, AP

2. COTTERJOINT
Mr.S.Saravanakumar, AP
Acotter joint isusedto connect rigidly two co-axialrods or bars
which are subjected to axial tensile or compressive forces . It isa
temporaryfastening.
Acotter isaflat wedge shapedpieceof rectangular cross section and
its width is tapered (either on one sideor on both sides)from one
end to another for aneasyadjustment.
.
Socket Cotter
Spigot

3. APPLICATIONSOF COTTER
Mr.S.Saravanakumar, AP
1.Connectionof the piston rod with the cross heads
2.Joiningof tail rod with piston rod of awet air pump
3.Foundationbolt
4.Connectingtwo halvesof flywheel (cotter anddowel
arrangement)

4. Designof Spigotand SocketCotter
Mr.S.Saravanakumar, AP
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 of cotter,
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.

5. Mr.S.Saravanakumar, AP

6. Mr.S.Saravanakumar, AP

7. Mr.S.Saravanakumar, AP

8. 1. Failureoftherod (Spigot)in
tension
Mr.S.Saravanakumar, AP
P=AreaxTensilestress

9. 2. Failureof spigotintensionacross the
weakestsection(or slot)
Mr.S.Saravanakumar, AP
Area Resisting=
P
d2

10. 3. Failureof the rod(spigot)orcotter in
crushing
Mr.S.Saravanakumar, AP
• P=d2xt xσc
d2

11. 4. Failureof the socketintension across
the slot
Mr.S.Saravanakumar, AP
AreaResisting=
LoadP=

12. 5. Failureofcotterinshear
Mr.S.Saravanakumar, AP

13. 6. Failureof the socketcollarin
crushing
Mr.S.Saravanakumar, AP

14. 7. Failureofsocketendin shearing
Mr.S.Saravanakumar, AP

15. 8. Failureofrod(Spigot)endin
shear
Mr.S.Saravanakumar, AP

16. 9. Failureof spigotcollarincrushing
Mr.S.Saravanakumar, AP

17. 10. Failureof the spigotcollarin
shearing
Mr.S.Saravanakumar, AP

18. Problem1
Mr.S.Saravanakumar, AP
Design and draw a cotter joint to support a load
varying from 30 kN in compression to 30 kN in
tension. Thematerial usedis carbon steel for which
the following allowable stressesmay be used. The
load is applied statically. Tensile stress =compressive
stress =50 Mpa shear stress = 35 MPa crushing
stress=90 MPa.
t =Thicknessof cotter. Itmay be taken asd2/4.
Thelength of cotter ( l) is taken as4 d.

19. Problem2
Mr.S.Saravanakumar, AP
Design a cotter joint to transmit a load of 90 kN in
tension or compression.Assumethe following
stressesfor socket, spigot andcotter.
Allowable tensile stress =90 Mpa
Allowable crushing stress =120 Mpa
Allowable shear stress =60 Mpa.

20. Problem3
Mr.S.Saravanakumar, AP
Two rod ends of apump are joined by meansof
acotter and spigot and socket at theends.
Design the joint for an axial load of 100 kN
which alternately changesfrom tensile to
compressive. Theallowable stresses for the
material used are 50 MPain tension, 40MPa
in shear and 100 MPain crushing