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  • Syed Sagheer Abbas Rizvi

What are Spur Gears and how do they work?

The most common and straightforward form of gear is a spur gear. This is primarily because they are fairly simple to create and have a wide variety of uses. They have straight, parallel teeth that are cylinder-shaped by design. The profile of their teeth is involuntary. The gear can generate radial forces but not axial forces because of its teeth configuration.

A very prevalent mechanical component is the gear. They are present in almost every mechanical device with rotating components. These mechanical transmission components, which have teeth, are used to transmit motion and power between machine parts. This article examines one particular gear type, the spur gear, and describes what it is and the various machines that employ it.

How Spur Gears work

Spur gears are the gear type that isutilized the most frequently. They are also known as straight-cut gears because they have circular gear bodies with straight teeth that are cut or inserted parallel to the gear's shaft.

These gears use parallel axes designed to transmit motion and power when they are paired. They can be coupled with another spur gear, an internal gear (such as in a planetary gear system), or a gear rack depending on the application (such as in a rack and pinion gear pair). Their shafts are coplanar and parallel.

The spur gear tooth design's simplicity enables both greater precision and simpler manufacturing. Spur gears also can handle high speeds and loads while maintaining high-efficiency rates. Their involute profile is the cause of the absence of an axial load.

The most popular type of gearing system is one with an involute gear profile. The profiles of the teeth are the involutes of a circle in an involute gear. A curve that depends on another shape or curve is called an involute. It represents the route taken by the ideal string's end as it curves.

Spur gears only generate radial forces as a result of their shape. At the place where the involutes meet, a gear tooth from one involute mesh with a gear from another involute. The line of force is parallel to the two base circles, and the point of contact moves along the tooth surfaces as the gears rotate.

The angular velocities of the gears must maintain a constant ratio throughout the mesh, according to the fundamental law of gearing, which is followed by the gears in this manner.

Spur gears come in two varieties: internal and exterior gears. The interior of the cylinder has been carved with teeth for the internal gears. Compared to their external counterparts, they are smaller. This is caused by how closely the shafts are spaced.

For planetary gear drives, they are frequently employed. External spur gears, on the other hand, have teeth that are carved onto the exterior of the cylinder. They fit inside the internal gear and rotated in opposite directions while meshing together.

Numerous metals and polymers, including nylon and polycarbonate, can be used to create spur gears. Spur gears made of plastic make less noise but are weaker and have lower loading capacities. Spur gears often have good transmission efficiency because, in contrast to other gear types, they don't suffer from significant slippage losses.


Spur gears are employed in a variety of mechanical applications, including clocks, electric screwdrivers, pumps, watering systems, material handling machinery, power plant

, and washing and drying machines, for a wide range of speed ratios.

More than two spur gears can be used in a gear train to give a higher gear reduction if it is required for a particular application. They work well in applications that call for a drop in speed and an increase in torque, like machinery for crushing.

Spur gears are frequently used in aircraft engines but are less common in automobiles because they tend to be noisier than other types of gear. The teeth collide and make noise each time a spur gear's tooth engages with a tooth in another gear.


Overall, spur gears are ideal for applications requiring torque multiplication and speed decrease, such as crushing machines. Although they are less preferred for passenger cars, they are frequently used in train and airplane engines. They are useful tools.

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