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Types of Gears

Updated: Oct 21, 2020

What is a gear?

A gear is a mechanical element with teeth on the edge of the gear. The gear transmits power through continuous meshing motion. With the development of industrial production, the smoothness and durability of gear operation have been valued. Gears can be divided into different types according to their shape and the position of the shaft. Below we have listed some types of gears for your reference.


Parallel Axes Gears

1. Spur Gear

The spur Gear is a classification of gears, and the shape is cylindrical. This kind of gear is usually used in the industry to control operating speed and transmit mechanical motion. Each of its teeth is parallel to the axis of rotation, which can move between the gears more stable. Its main advantages are fast transmission efficiency, a large amount of electricity transmission, easy installation, durability, and reliability.

According to different uses, there are two classifications of spur gears, one is plastic spur gears and the other is metal spur gears. Plastic spur gears are mostly used in light industry, such as food manufacturing. Because it is not easy to rust, and its weight is lighter, it is suitable for mass production industries. Metal spur gears are used in heavy industry. Because it is stronger, durable, heat-resistant, and can carry more weight.

2. Gear rack/Rack and Pinion

The gear rack is a special gear, and its teeth are distributed on the elongated body. The gear rack is a bar-shaped part that matches the pinion. Rack and pinion is linear motion, it can convert rotary motion into linear motion. The tooth profile of the rack is a straight line instead of an involute, which is equivalent to an infinite cylindrical gear with an index circle radius. There are two types of gear racks which are straight gear rack and helical gear racks. A straight gear rack is used to pair with spur gear; a helical gear rack is paired with helical gear.

3. Internal gear

The outer ring of the internal gear is smooth, and the teeth are on the inner surface. The internal gear can mesh with the spur gear.

The principle of internal gear and external gear is the same. It's just that the internal teeth are equivalent to the teeth of the external gear. For example, the top cut of the internal gear is equivalent to the undercut of the external gear. Internal gears are suitable for use in planetary gear mechanisms and gear couplings. The most common planetary gear mechanisms are solar-type, planetary type, and star type. According to the different types, input, and output, they can produce different transmission speed ratios and rotation directions.

4. Helical gear

A helical gear is the meshing method of two helical gears, distinguished by the different directions in which they transmit force in space. The front edges of the teeth of the helical gear are not parallel to the axis of rotation but form an angle. The greater the angle, the greater the degree of coincidence, which is more conducive to smooth movement and reduce noise. The advantages of this gear are strong carrying capacity, durability, smooth rotation, and low noise. Compared with spur gears, helical gears have higher rotational efficiency. Therefore, it is suitable for high-speed and heavy-duty operations.

5. Double helical gear

A double helical gear is a kind of gear, but has two sets of helical teeth and forming a V-shaped tooth. The double helical gear is due to the helical gear having a lateral force on the shaft. In order to eliminate this force, another set of opposite helical gears was installed to eliminate this force. Double helical gears have the advantages of higher coincidence, lower axial load, high carrying capacity, and stable operation. Compared with helical gears, their advantage is that half of the side thrust is balanced with the other half.

Intersecting Axes

1. Straight Bevel Gear

Straight bevel gears are the most widespread bevel gears. It is similar to a spur gear, with straight teeth and the way the teeth mesh in the same way, except that its shape is conical. Straight bevel gears are often used in low-speed applications or under static load conditions. For example, the marine industry, aviation industry, construction industry, etc.

2. Spiral Bevel Gear

The surface of the spiral bevel gear has helical teeth at 90 degrees. The advantages of spiral bevel gears are strong carrying capacity, high transmission ratio, stable transmission, and low noise. Therefore, it is widely used in mechanical transmission fields such as automobiles, aviation, and mining. The axis of the big wheel of the spiral bevel gear will intersect the axis of the small wheel.

There is another type of spiral bevel gears, called hypoid spiral bevel gears. Hypoid spiral bevel gear is a kind of bevel gear, and its large wheel axis and small wheel axis have a certain offset distance.

The zero bevel gear is also one of the spiral bevel gears, its twisting angle is zero degrees, and the thrust is less than that of the spiral bevel gear. Its function is the same as that of a straight bevel gear.

3. Mitre Bevel Gear

Mitre Bevel Gear is mainly used to change the direction of power transmission without changing the speed. It usually has a 90-degree shaft angle, which can effectively transmit power and movement. The transmission ratio of the Mitre Bevel Gear is 1:1 because it has the same number of teeth and the same radial pitch. The advantage of the Mitre Bevel Gear is that it can handle higher speeds and larger torque loads more smoothly and quietly.

Non-parallel and Nonintersecting Axes Gear

1. Worm Gear

A worm gear is usually used to transmit the power between two interleaved shafts. The worm gear is mainly composed of a shaft with a spiral, which meshes with the gear to drive the gear. Worms are usually made of harder materials, while worm wheels are made of softer materials. The worm gear is suitable for heavy machinery and household equipment.

2. Screw Gear

The screw gear has a pair of disjoint helical gears. This pair of helical gears is called a 45-degree torsion angle, so it can also be called a crossed helical gear. It transmits power without intersecting. Its disadvantage is its low carrying capacity because it has only one intersection, it is not suitable for high-power transmission.


The above are some of the more common and commonly used gears. Some special gears are also used in the industry, such as Face Gear, Enveloping Gear Pair, and so on. If you want to know more about the categories or details of gear, you can consult our professionals at 011-7001 7687 or email us to

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