Definition of Spare Parts

The term “spare” in English has its roots in Old English “spær,” which means “sparing, scant.” This Old English term, in turn, is derived from the Proto-Germanic sparaz.
Spare parts are components or pieces of a device, machinery, or vehicle that can be replaced when failures or wear occur. These replacement parts are designed to be compatible with the original object and can be supplied by either the object’s manufacturer or specialized third parties in the production of spare components.

Spare Parts Classification: commercial uses

From a commercial perspective, spare parts can be classified into three types:


(Original Equipment Manufacturer): These are replacement parts that are produced by the same manufacturer that produced the original object. These parts are generally considered to be of high quality and perfectly compatible with the original object.

Alternative or Aftermarket Parts

These are replacement aftermarket parts that are often not produced by the original manufacturer of the vehicle or machine, but by a separate company. These parts can be used as economical substitutes for OEM parts.

Used or Second Hand Parts

These are oem parts or aftermarket parts that have been regenerated and resold at a lower price.
Additionally, there are original equipment parts that cannot be classified as spare parts, as they are installed as an original part of the machine and not as a replacement part.

Spare Parts Classification: Use and Position

Spare parts can also be classified based on their use and position. These classifications can vary depending on the context and terminology because, as we will see, the distinctions are subtle and sometimes the terms are used interchangeably.


These are parts that are designed to be consumed and replaced during the normal use of a device or a machine. These can include things like brake pads on a car, blades on a saw, or the bucket teeth of an excavator.

Service Parts

As the word itself suggests, these are parts that are replaced during a service or scheduled maintenance. These are not specifically built to be consumed and replaced but are when they reach the end of their life. These can include things like oil filters or transmission belts.

Interchangeable Parts

These are parts that can be replaced by another identical part. These parts are designed and manufactured to be exactly the same, so they can be swapped without altering the performance of the device or machine. Examples of this include screws and bolts, this concept is fundamental for mass production and industrial efficiency.
The most generic definition would be service parts. As the word itself suggests, it falls into the service, so in the parts changed during the service phase.

Bearings, pins and bushings

Bushings and bearings would fall into the category of spare parts and could be considered both as wear parts and service parts, depending on the context. They are essential components that allow the fluid movement of other mechanical parts and can be replaced when wear or failures occur. Furthermore, since bushings can be manufactured to be exactly the same as each other, they can also be considered as interchangeable parts. However, the specific classification can vary depending on the specific application and context.

Speaking of bushings, you can always request our steel bushings catalog for more information.

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Differences Between Bushings, Bushes, and Bearings

boccole, bussole o bronzine

Bushings, bushes and bearings are often used interchangeably to refer to the same mechanical component: an element inserted between two parts to reduce friction during movement. However, it’s important to note that these terms, while similar, are used with subtle differences depending on the specific context and application

Bushings or Bushes terminology 

This is a general term, that refers to a cylindrical element between two parts to reduce friction during movement. The term originates from the Latin word “buxida”, meaning box.

In the context of mechanical engineering, the terminology can differ based on the variant of English being used. In American English, the term bushing is typically used. However, in other parts of the world where English is spoken, you might hear either bush.

Usage and Applications

Bushings are essential components utilized across various industries. They are commonly employed in agriculture, construction, mining, and manufacturing equipment.

In agriculture, bushings ensure seamless operation in tractors, harvesters, and other farming machinery by facilitating movement in linkages and steering mechanisms. Similarly, in construction equipment like excavators and loaders, bushings enable essential components such as boom arms and buckets to move efficiently.

In the mining sector, bushings withstand harsh conditions and heavy loads, contributing to the functionality of equipment like conveyor systems and drilling machinery. In manufacturing, they support rotating and sliding shafts in machine tools, presses, and industrial robots, ensuring smooth operation.

The term is often used to define the position of the bushing within a mechanical system, such as reduction bushing, traction bushing, centering bushing, guide bushings, etc.

Bushings vs Bearings

While a bushing is a type of bearing, not all bearings are bushings. Bearings encompass a broader category that includes elements like ball bearings, roller bearings, and bushings. Specifically, bushings are a type of plain bearing that provide low-friction support for rotating shafts without the need for rolling elements.

Sleeve bearings and Sliding Bearings

The bushing is a type of bearing with specific characteristics. Often, the term “bearing” is used to refer to bushings, with terms that refer to use: sliding bearings, sleeve bearing.

In the mechanical industry, a sleeve typically denotes a cylindrical tube that serves to shield or encase another component. However, when the term sleev” is combined with bushing, it specifically refers to a type of bushing known as a sleeve bushing.

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