Important Point
Application of Cotter Joint:
A cotter joint is used to support the axial load between two coaxial rods, which is the tensile and compressive load. Although a cotter joint will resist the rotations of one rod relative to the other, it should not be used to join a rotating shaft.
- This joint use between the pistons rod and the tail of the pump rod.
- Cotter’s joints are used between the slide spindle and the fork of the valve mechanism.
- Cotter and Dowell arrange to join two parts of a flywheel.
- Foundation bolt: mainly used for fastening foundation and construction heavy machines
- In an automobile engine, the cotter joint is used to connect the extension of the piston rod
- with the connecting rod in the crosshead.
- The Kottar joint has historically been used to connect connecting rods to steam engines and pumps of dumping mines.
- It is used in bicycles to connect the paddle to the sprocket wheel.
- Use a wet air pump to join a tail rod with the piston rod.
- It is used to connects two rods of equal diameter subjected to axial forces.
What Is a Cotter Joint?
- A cotter joint, also known as a spigot and socket joint, is a method of temporarily connecting two coaxial rods.
- A rod is fitted with a spigot, which fits inside a socket at one end of the other rod. The slots in the socket and spigot align so that a cotter can be inserted to close both rods together.
- This joint is used to support axial loads between two rods, tensile or compressed.
- The cotter used within cotter joints is a flat wedge shape grind of steel; it is mainly used to connect rigid two rods that transmit motion in the axial direction, without rotation.
The cotter joint assembly consists of three components: spigot, socket, and couture.
- The spigot of Cotter Joint.
- The socket of Cotter Joint.
- Cotter of Cotter Joint.
#1. The Spigot of Cotter Joint
- The spigot is the male part of the joint, rectangular slot for passing the cotter throughs it.
The spigots have a collar that rests against the end of the sockets.
#2. The Socket of Cotter Joint
- This is the female part of the joint; there is also a rectangular slot to pass the cotter through it. It has circular holes in which the spigot is fitted.
#3. Cotter of Cotter Joint
- Couture is a wedge-shaped piece of metal that actually connects two parts that are non-rotating. The socket operates in a slot in both the socket and rod. It is not suitable for connecting a rotating shaft that transmits torque.
- The axes of joining rods must be matched. The above three parts, spigot, sockets, and cotters, together form a cotter joint. One of the two connecting rods consists of a spigot and a socket.
- First, the spigot enters the circulars hole of the sockets, and then the cotter fits tightly into the rectangular slot of the spigot and the socket that matches each other.
- This fixes the cotter spigot and socket together. The cotter is fitted into a tapered slot and remains in its position due to the wedge action. It is caused by the taper. A tapper is used to lock the joints.
- Generally, the value of the taper on the cotter ranges from 1 to 48 in 24 and provides mainly two benefits: first, this taper is easy to remove and separates the joint with a simple process. Second, the tapper also ensures joint stiffness and prevents parts from loosenings.
- Finally, the cotters are in contact with the spigots on one side and a fixed distance from the socket slot, and on the other is a fixed distance from the spigot slot in contact with the socket.
- The intended distance is typically 1.5 to 3 mm. The cotter closed due to the friction force of the contact surfaces.
- A very well known example is the joining of the piston rod extension with the connecting rod into the crosshead assembly. A cotter joint was favored because they are relatively easy to design and manufacture, they produce rigid connections, and they are not prone to loose work in reciprocating machinery.
- These components were historically connected to pumps for the extraction of connecting rods and mines in steam engines. Cotter’s joint has been preferred because it is relative to simple to design and manufacture, make a rigid connection, and do not loosen in reciprocating machinery.
Types of Cotter Joint:
There are three types of cotter joint for connecting two rods by one coater:
- Socket and spigot cotter joint.
- Sleeve and cotter joint.
- Gib and cotter joint.
#1. Socket and Spigot Cotter Joint
- A cotter joint knows as a socket, and a spigot joint is a method of temporarily connecting two coaxial rods, one end of the rod is provided with a socket type, and the other end of the other rod is inserted into the socket.
- The end of the rod goes into a socket, also known as a spigot.
- A rectangular hole is built into the sockets and spigot. A cotter is working tightly through the hole to form a temporary connection between the two rods.
- The load is usually acting axially, but it changes its direction. And therefore, the cotter joint must be designed to carry both tensile and compressive loads.
- Compressive load-carrying load on the connective by the connector.
#2. Sleeve and Cotter Joint
- Sleeve and cotter joint is a type of joint use that usually connects two identical coaxial cylindrical rods. It includes one sleeve and two wedge-shaped tapered coaters. Suitable slots cut into sleeves and cylindrical rods.
- These slots have a cotter mount. The taper of the cotters is usually 1 in 24. It may be noted that the taper sides of two cottars must face each other.
- The clearance is such an adjustment that when the coaters are driven into two rods, they come close to each other and thus tighten the joint.
- The sleeve and cotter joint is the simplest couture joint in existence. It is quite rigid and can carry both tensile and compressive loads. It can be easily assembled and disintegrated. The joint can also be used to connect similar pipes, tubes.
- Rectangular rods and uneven cylindrical rods cannot be connected using this joint. A sleeve and cotter joints do not allow angular deviation between its cylindrical members. It cannot connect cylindrical members that undergo rotation.
#3. Gib and Cotter Joint
- A gib and couture joint typically use either the strap end or the larger end of the connecting rod. In some cases, when the cotter is run alone, i.e., without gib.
- The friction between its ends and the inside slot in the strap causes the edges of the strap to open outward.
To prevent this, the gib is used that holds the ends of the strap together. In addition, the gator provides a larger bearing surface for the cotter to slide as the holding power increases.
Thus, the friction of the cotter reduces the tendency to slacken back. Gib also enables parallel holes to be used. Gib and cotter joints are used for square or rectangular cross-section rods. The end of one rod fits into the end of the other rod, which is designed as a strap.
A gib with a cotter is used to make these joints. The Gib is potentially a cotter but has two gib heads at its ends. The thickness of the whip is the same as the gib and the cotter.
- When a gib is used, a tape cotter is provided on one side, and the gib is always on the outside.
- When two Gibbs are used, the cotter is provided with both sides taped.
- Sometimes, a small set screw is used through rod jamming against the cotter to prevent the cotter from loosening.
Application of Cotter Joint:
A cotter joint is used to support the axial load between two coaxial rods, which are the tensile and compressive loads. Although a cotter joint will resist the rotation of one-rod relatives to the other, it should not be used to join a rotating shaft.
- This joint use between the piston rods and the tail of the pump rods.
- Cotter’s joints are used between the slide spindles and the fork of the valve mechanism.
- Arrangement of cotter and dowel to join two parts of a flywheel.
- Foundation bolts: mainly used in fastening heavy machines for foundations and construction
- In an automobile engine, a cotter joint is used to connect the extension of the piston rod with the connecting rod in the crosshead.
- The cotter joint has historically been used to connect connecting rods to steam engines and pumps for the extraction of mines.
- It is used in a bicycle to connect the paddle to the sprocket wheel.
- Use a wet air pump to join a tail rod with the piston rod.
- It is used to connects two rods of equal diameter subjected to axial forces.
Failure of Cotter Joint:
When the socket joint was tightened into the socket and spigot slot, it was exposed to shear stress. Then if the cotter is loose, the cotter will bend.
Various methods of failures in the cotter joint are discussed below:
- Tension failure of rods.
- Spigot failure under stress in the weakest section.
- Rod or cotter failure in crushing.
- Socket failure under tension in the slot.
- Shear failure in shear.
- Socket collar failure to crush.
- Socket failure in shearing.
- Rod ends failure in shear.
- Spigot collar failure to crush.
- Spigot collar failure in shear.
- Cotter failure in bending.
In this article, we learn about the cotter joint, a type of mechanical joint used to connect rigid two rods that transmit motion in an axial direction, without rotation.
These joints may be subject to tensile or compressive forces with the axes of the rods. A very well known example is the joining of the piston rod extension with the connecting rod in the crosshead assembly.
Also, Read: Working of Venturimeter | What Is a Venturimeter | Construction of Venturimeter | Working of Venturimeter
Advantages of Cotter Joint:
- Cotter joints can be made easily, and parts are always in the same relative position after retrieval.
- Joints can be used to connect similar pipe tubes.
- Assembling and removing parts of the cotter joints is quick and easy and does not require special efforts.
- Cotter joints are simple and easy to manufactures and obtain in the markets.
- It is quite rigid and can carry both tensile and compressive loads.
Disadvantages of Cotter Joints:
- Rectangular rods and uneven cylindrical rods cannot be added using these joints.
- Sleeve and cotter joints that cannot connect cylindrical members undergo rotation.
Failure of Cotter Joint.
Frequently Asked Questions (FAQ)
Application of Cotter Joint
A cotter joint is used to support the axial load between two coaxial rods, which are the tensile and compressive loads. Although a cotter joint will resist the rotation of one-rod relatives to the other, it should not be used to join a rotating shaft.
Cotter Joint
A cotter joint, also known as a socket and spigot joint, is a method of temporarily joining two coaxial rods. One rod is fitted with a spigot, which fits inside a socket on one end of the other rod. Slots in the socket and the spigot align so that a cotter can be inserted to lock the two rods together.
Cotter Pin Joints
5 Joint Pins, Also Called Cotter Pins and T-Pins, are parts to make Teddy Bear Joints and Doll Joints For joint movement of arms, legs, and neck. Joints Pins are used with Millboard Hardboard Discs and Metal Washers. Available in Size 20mm to 24mm with 7mm T for For Teddy Bear and Doll Joints.
Knuckle and Cotter Joint
- The area of a rectangular section extends on both sides in the direction of the width.
- We add the pin ⊥ to the axis of the arm add the arm to the arm, then add the pin.
- It can be better than Cotter Socket and Spigot joints.
- The taper on the pin is 1 in 24.
Socket Spigot Cotter Joint
In a socket and spigot cotter joint, one end of the rods (say A) is provided with a socket type of end as and the other end of the other rod (say B) is inserted into a socket.
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