8 Common Engineering Components Used in Machines Today

8 Common Engineering Components Used in Machines Today

A machine is an apparatus that uses mechanical power to fulfill certain tasks. Today’s machines consist of several parts, and each part serves a distinctive function. What may come as a surprise to some is that both sophisticated machines and more ordinary devices have a lot of parts in common. What are these key components that make these machines work? Which parts are often the most necessary in helping machines complete their individual purposes?

Here’s a brief guide on the three basic types of machine element—structural components, mechanisms, and control components—that are used in modern-day engineering. In this feature, you will learn a little about individual components and what their real-life applications are. This should give you some perspective on just how different—but also just how alike—many of the world’s machines actually are.

Structural Components

Part of understanding how complex machines work is being able to break them down into simpler parts. These parts are called structural components. Some examples are the following.


A bearing is meant to do two things: reduce friction between moving parts, and constrain relative motion to the motion that’s desired. The motion permitted by the bearing depends on its design and application. One example is a bearing in a drawer, which permits linear motion. Another example is a rotary bearing in a motor, pulley, or pump that permits rotary motion, or rotation around a fixed axis.


An axle is a spindle or a rod which passes through rotating wheels or gears. The axle is what transfers both torque and power from a machine’s engine to its wheels. Thus, axles are key components to the wheel systems of vehicles, involved in actions such as steering and braking. They’re manufactured to be robust because they must sustain the weight of passengers, cargo, and the vehicle itself.

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A fastener is a component that mechanically affixes two or more objects together. Fasteners can be made of a variety of materials, such as stainless steel or metal alloys. There are the type that permanently join components together. Conversely, there are non-permanent fasteners that can be dissembled without compromising the workings of the rest of the structure.

Fasteners are incorporated into a wide variety of machines, from aircraft to simple household appliances. In 2008, it was estimated that 200 billion fasteners were used annually by consumers in the USA.


In machines, the mechanisms are what control movement. They convert input forces and movement into the desired output forces and movement for the application. Two familiar mechanisms in machines are described below.


Gears, which are distinguishable by their “teeth,” are meant to mesh with other gears in order to transmit torque. The gear’s teeth serve the key purpose of preventing any slippages in the transmission. Gears are commonly made of steel, although plastic is also widely used. Two or more gears that work in a sequence are referred to as gear trains.

The change in torque that’s facilitated by the gears creates a mechanical advantage. You can see this at work if you examine gears in clocks, instruments, and motorized devices.


Cams are sliding or rotating pieces in mechanical linkages that transform rotary motion into linear motion. The cam itself follows a circular path, then it typically strikes a lever—called a cam follower—to set off the linear motion.

One type of cam is the disc or plate cam that actuates switches in a dishwasher. Another type is the cylindrical cam that drives sequential manual transmissions for a motorcycle.


Control Components

The control components are the parts in a machine that direct or regulate the device’s behavior through the use of control loops. Three of the most well-known control components are detailed below.


A switch is a device, typically an electromechanical one, that controls the continuity between two points. Switches are classified according to the type of connection they make. The four contact variations of switches are the following:

  • Single-pole, single-throw (SPST)
  • Single-pole, double-throw (SPDT)
  • Double-pole, single-throw (DPST)
  • Double-pole, double-throw (DPDT)

The switches you see in everyday applications range from simple manual light switches to the more complex kind. Some can activate after sensing an element like pressure or temperature.


A sensor is a component that can pick up changes in the environment, then send information to other electronics for further action. There are simple tactile sensors, like the type used in elevator buttons. There are also the more sophisticated sensors used in biotechnology, which can detect analytes or subjects of interest for chemical analysis.


An actuator needs two things in order to work: a control signal and a source of energy. The control signal may be human power, electric voltage, or hydraulic pressure among others. Once the actuator receives this signal, it converts the source energy into mechanical motion. Some examples of actuators in modern-day machines are the hydraulic cylinders used in construction equipment and the stepper motors used in computer hard drives.

It is the engineer’s work to learn about these machine components and intelligently combine them for a necessary application. This is oftentimes tedious, oftentimes rewarding work. After all, so many intricate parts are involved in fulfilling a multitude of machine processes.

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