Mechanical joint

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title: "Mechanical joint" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["kinematics", "rigid-bodies", "mechanical-engineering", "hardware-(mechanical)", "fasteners"] description: "Section of a machine which is used to connect one mechanical part to another" topic_path: "engineering" source: "https://en.wikipedia.org/wiki/Mechanical_joint" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Section of a machine which is used to connect one mechanical part to another ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/a/a5/Knuckle_joint_on_locomotive.JPG" caption="A knuckle joint on a locomotive, seen behind the pin joint of the eccentric crank. Ball-point pen included for size."] ::

A mechanical joint is a section of a machine which is used to connect one or more mechanical parts to another. Mechanical joints may be temporary or permanent; most types are designed to be disassembled. Most mechanical joints are designed to allow relative movement of these mechanical parts of the machine in one degree of freedom, and restrict movement in one or more others.

Pin

Main article: Revolute joint

Prismatic

Main article: Prismatic joint

A prismatic joint provides a linear sliding movement between two bodies, and is often called a slider, as in the slider-crank linkage. A prismatic pair is also called as sliding pair. A prismatic joint can be formed with a polygonal cross-section to resist rotation.

The relative position of two bodies connected by a prismatic joint is defined by the amount of linear slide of one relative to the other one. This one parameter movement identifies this joint as a one degree of freedom kinematic pair.

Prismatic joints provide single-axis sliding often found in hydraulic and pneumatic cylinders.

Ball

Main article: Ball joint

In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles. They are used on virtually every automobile made and work similarly to the ball-and-socket design of the human hip joint.

A ball joint consists of a bearing stud and socket enclosed in a casing; all these parts are made of steel. The bearing stud is tapered and threaded, and fits into a tapered hole in the steering knuckle. A protective encasing prevents dirt from getting into the joint assembly. Usually, this is a rubber-like boot that allows movement and expansion of lubricant. Motion-control ball joints tend to be retained with an internal spring, which helps to prevent vibration problems in the linkage.

The "offset" ball joint provides means of movement in systems where thermal expansion and contraction, shock, seismic motion, and torsional motions, and forces are present.

Cotterpin

Main article: Cotter (pin)

This is mainly used to connect rigidly two rods which transmit motion in the axial direction, without rotation. These joints may be subjected to tensile or compressive forces along the axes of the rods. The very famous example is the joining of piston rod's extension with the connecting rod in the cross head assembly.

Advantages:

• Quick assembly and disassembly is possible
• It can take tensile as well as compressive force.

Application:

• Joint between piston rod and cross head of a steam engine
• Joint between valve rod and its steam
• A steam engine connecting rod strap end
• Foundation bolt

Bolted

Main article: Bolted joint

Advantage:

• Joints are easily assembled/ disassembled by using a torque wrench or other fastener tooling.
• Clamped members can be axially tensioned at variable preloads.

Disadvantage:

• Threaded components can fail from fatigue failure.
• Joints can come loose, requiring re-torqueing.

Application:

• Pipe flanges
• Automotive engines
• Foundation bolts

Screw

Main article: Screw joint

Universal

Main article: Universal joint

References

References

1. (1985). "Design of mechanical joints". CRC Press.
2. Norton, Robert L.. (2008). "Design of Machinery". McGraw Hill Higher Education.
3. Robotics Research Group. "Joint Types". University of Texas at Austin.
4. Bumbeck, Mike. "Ball Joints - How to Keep Your Front Suspension Together". Mobile Oil.
5. (2010). "Your Car's Ball Joints - The Pivotal Part of the System". California Dept. of Consumer Affairs, Bureau of Automotive Repair.
6. "Industrial Ball Joints - Dannenbaum LLC Ball Joints".
7. (12 November 2017). "Bolted Connections and Advantages of Bolted Connections - Civil Snapshot".
8. Hudgins, Alex. (Aug 2014). "Fatigue of Threaded Fasteners". Advanced Materials & Processes.
9. (2015-08-20). "Why Do Fasteners Become Loose? {{!}} HARDLOCK Industry".
10. "Bolted Joint - Bolted Joint And Gasket Interface {{!}} Measure Bolted Joint Tension {{!}} Bolted Joint Force {{!}} Gasket Contact".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::