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Spur Gears

Last updated date: 05th Mar 2024
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Introduction to Spur Gears

Spur gears, also known as straight-cut gears, are the most basic type of gear. They are made up of a cylinder or disc with teeth that protrude radially. The tooth faces are straight and parallel to the axis of rotation when seen at 90 degrees from the shaft length.

Spur Gear

Spur Gear

What is Spur Gear?

One of the most common forms of precision cylindrical gears is spur gears. These gears have a straightforward construction with straight, parallel teeth arranged around the circumference of a cylinder body with a central bore that fits over a shaft. The gear is machined with a hub in several forms, thickening the gear body around the bore without modifying the gear face.

What are the Types of Spur Gears?

Spur gears are split into two types: external and internal.

  • "External gears" are gears with teeth on the exterior of the cylinder. . An exterior gear can mesh with either an internal or external gear. When two exterior gears mesh, they spin in opposite directions

  • "Internal gears" are gears with teeth on the inside of the cylinder. Only an internal and external gear can mesh, and both gears must revolve in the same direction. Internal gear assemblies are more compact than external gear assemblies due to the close arrangement of shafts.

Pitch Circle

The pitch circle is the distance between the faces of two teeth. It separates the teeth of gear into the top of the tooth, the addendum, and the bottom of the tooth, the dedendum. Pitch circles between gears should be tangent to one another if a gear system is properly built.

Pitch Circle

Pitch Circle

  • Diameter pitch - The diametral pitch of a gear is a function of its pitch circle and equals the number of teeth per inch. It determines what size and kind of gear are required to interlock with another gear.

Types of Spur Gear

  • Spur gears

  • Helical gears

  • Bevel gears

  • Worm gears


Spur Gear Diagram



Brief Explanation of Spur Gear


Brief Explanation of Spur Gear




Spur Gear


Spur Gear


Spur Gear Uses

Here are some applications of spur gear.

  • Tooling, allowing us the flexibility to fabricate standard or custom cold rolled spur gears designed to meet exact specifications across a wide range of industrial applications.

  • These spur gears are also used for industrial purposes - in the field of transmissions, speed reducers, conveyor systems, machining tools, etc.

  • Increasing and decreasing power - Spur gears are found in washing machines, blenders, clothes dryers, construction equipment, pumps, and conveyors and are used to enhance or decrease the torque or power on a device. 

  • Road roller - A set of spur gears in a road roller converts the engine's fast rotating speed into the wheels' slow rotational speed. Because of this improvement, a road roller is able to move its heavy roller.


Spur Gear in Train

Spur Gear in Train

Solved Examples

1. What are the benefits of spur gear?

Ans: Simple design, precise and accuracy, low production cost, gear reliability, spur gear efficiency, straight teeth.

2. How to choose the right spur gears?

Ans: Selecting by torque and speed, identifying through pitch, idler gear, stress calculations and finally by the type of material.


A spur gear is a cylindrical toothed gear with teeth parallel to the shaft that is used to convey mechanical motion between shafts while also controlling speed, power, and torque.

The design, structure, and materials of a spur gear determine its performance. The fabrication of a spur gear, which includes the use of high quality materials and stringent and precise dimensional compliance that is used to establish a spur gear's function, is an important component of its creation.

Spur gears are manufactured using a variety of technologies, including forging, blank machining, cutting, casting, powder metallurgy, and computer numeric controlled manufacturing, to mention a few.

FAQs on Spur Gears

1. What are the materials used to manufacture the spur gear?

Polyacetal (POM) is the plastic material, cast iron, stainless steel, aluminium alloys, and steel in spur gears.

2. What are the processes included during the manufacture of spur gear?

Milling process, hobbing process, gear shaping, gear stamping process, cold drawing, spur gear roll forming and finally, the forging is done.

3. What are the advantages of spur gear?

Simple and compact design, constant speed drive, reliability, cost-effectiveness and efficiency.

4. What are the spur gear terms?

Pitch circle, diameter pitch, centre distance, module, outside diameter, whole depth and pressure angle.

5. Why is it called spur gear?

A spur gear is a type of gear that has teeth that protrude from a cylindrical surface. When spur gears are mounted on parallel shafts, the edge of each tooth is parallel to the axis of rotation, and they mesh together.