Socket and Spigot Cotter joint

Design Procedure for Socket and spigot Cotter JOint

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

2. COTTER JOINT Mr.S.Saravanakumar, AP 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. . S o c k e t C o t t e r S p i g o t

3. APPLICATIONS O F COTTER Mr.S.Saravanakumar, AP 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)

4. Design of Spigot and Socket Cotter 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 = Thickness of spigot collar, d4 = Diameter of socket collar, c = Thickness of socket collar, b = Mean width of cotter, t = Thickness of cotter, l = Length of cotter, a = Distance from the end of the slot to the end of rod, σ t = Permissible tensile stress for the rods material, τ = Permissible shear stress for the cotter material, and σ c = Permissible crushing stress for the cotter material.

5. Mr.S.Saravanakumar, AP

6. Mr.S.Saravanakumar, AP

7. Mr.S.Saravanakumar, AP

8. 1. Failure of the rod (Spigot) in tension Mr.S.Saravanakumar, AP P= Area x Tensile stress

9. 2. Failure of spigot in tension across the weakest section (or slot) Mr.S.Saravanakumar, AP Area Resisting= P d 2

10. 3. Failure of the rod (spigot) or cotter in crushing Mr.S.Saravanakumar, AP P = d 2 x t x σ c d 2

11. 4. Failure of the socket in tension across the slot Mr.S.Saravanakumar, AP Area Resisting = Load P= .

12. 5. Failure of cotter in shear Mr.S.Saravanakumar, AP

13. 6. Failure of the socket collar in crushing Mr.S.Saravanakumar, AP

14. 7. Failure of socket end in shearing Mr.S.Saravanakumar, AP

15. 8. Failure of rod(Spigot) end in shear Mr.S.Saravanakumar, AP

16. 9. Failure of spigot collar in crushing Mr.S.Saravanakumar, AP

17. 10. Failure of the spigot collar in shearing Mr.S.Saravanakumar, AP

18. Problem 1 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. The material used is carbon steel for which the following allowable stresses may be used. The load is applied statically. Tensile stress = compressive stress = 50 Mpa shear stress = 35 MPa crushing stress = 90 MPa. t = Thickness of cotter. It may be taken as d 2 /4. The length of cotter ( l ) is taken as 4 d.

19. Problem 2 Mr.S.Saravanakumar, AP Design a cotter joint to transmit a load of 90 kN in tension or compression. Assume the following stresses for socket, spigot and cotter. Allowable tensile stress = 90 Mpa Allowable crushing stress = 120 Mpa Allowable shear stress = 60 Mpa.

20. Problem 3 Mr.S.Saravanakumar, AP Two rod ends of a pump are joined by means of a cotter and spigot and socket at the ends. Design the joint for an axial load of 100 kN which alternately changes from tensile to compressive. The allowable stresses for the material used are 50 MPa in tension, 40 MPa in shear and 100 MPa in crushing