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Spur Gear

Spur gears are one of the most popular types of precision cylindrical gears. These gears feature a simple design of straight, parallel teeth positioned around the circumference of a cylinder body with a central bore that fits over a shaft. In many variants, the gear is machined with a hub which thickens the gear body around the bore without changing the gear face. The central bore can also be broached as to allow the spur gear to fit onto a spline or keyed shaft.

What Is a Spur Gear?

Spur gears are used in mechanical applications to increase or decrease the speed of a device or multiply torque by transmitting motion and power from one shaft to another through a series of mated gears.

The design and construction of a spur gear significantly influence its performance. To do their jobs effectively and efficiently, they need to be fabricated from high-quality materials and to precise dimensions. The dimensional measurements of each feature are integral to how a specific gear functions. As such, when an industry professional requires a new spur gear design or a replacement spur gear, it is imperative that they are familiar with the terms for each gear part and their respective measurements to ensure clarity and accuracy in the production or purchase order.

Spur Gear

Spur Gears Applications

Spur gears are used to transfer motion and power from one shaft to another in a mechanical setup. This transference can alter machinery’s operating speed, multiply torque, and allow for the fine-tuned control of positioning systems. Their design makes them suitable for lower speed operations or operational environments with a higher noise tolerance.Typical industrial applications include Transmission, Conveyor systems, Speed reducers, Engines, mechanical transportation systems,Gear pumps and motors, and Machining tools.

spur gear

Some commonly used spur gear terms include:

Pitch Circle

The circle derived from a number of teeth and a specified diametral pitch. The circle in which tooth spacing or profiles are established from which tooth proportions are constructed.

Outside Diameter

The diameter of the addendum circle, or the circle along the outermost points of a spur gear’s teeth. This measurement is the largest diameter spur gears have.

Pitch Diameter

Is the diameter of the pitch circle. This is where a spur gears angular velocity is measured. This is also a critical component for determining center distances between mating spur gears.

Center Distance

The distance between two gears, measured from the center shaft of one gear to the center shaft of the mating gear.


The depth of a tooth space below the pitch circle. Generally greater than the addendum of the mating gear to provide clearance.


The ratio of the reference diameter of the gear divided by the number of teeth. Module is the metric equivalent to diametral pitch.

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Spur Gear Video

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Types of Spur Gear

External Spur Gear

Internal Spur Gear

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Some FAQ

What Materials Are Spur Gears Made Of ?
Spur gears can be made from metals such as steel or brass, or from plastics such as nylon or polycarbonate. Gears made of plastic produce less noise, but at the expense of strength and loading capability.
What Is The Main Difference Between Spur Gear And Helical Gear ?

In spur gear, the teeth are parallel to the axis of the gear. In helical gear, teeth are inclined at an angle (called helix angle) with the gear axis. Spur gear imposes only radial load on bearings. Helical gear imposes radial load and axial thrust load on bearings.

Can A Spur Gear Mesh With A Worm Gear ?
Conclusion. Orthogonal worm gear pairs may be designed so as to engage a spur gear in mesh with a mating involute worm under a right shaft angle in the worm gear pair. The same is also valid with respect to two-starts worm gear pairs. Axial thrust in the spur gear is eliminated under such a scenario.
How Are Spur Gears Made ?
Most spur gears and helical gears are manufactured with the help of cutting. Yet, there are many other methods like casting, rolling and forging. In the case of plastic spur gears, in addition to tooth cutting such as with metal gears, injection molding is used depending on the quantity of production.

benefits of spur gears

"Spur gears feature a simple, compact design that makes them easy to design and install, even in limited or restricted spaces."

—— Simplicity

"Unlike other power and motion transmission components, spur gears are unlikely to slip during operation. Additionally, their durability decreases their risk of premature failure."

—— Reliability

"These gears increase or decrease shaft speed with a high degree of precision at a constant velocity."

—— Constant Speed Drive

"The simplicity of their design also allows for greater manufacturability, making them less expensive to fabricate and purchase even with highly specific or customized dimensions."

—— Cost-Effectiveness

"Spur gear systems have power transmission efficiencies between 95% and 99% and can transfer large amounts of power across multiple gears with minimal power loss."

—— Efficiency


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