What are Different Types of Gears and their Functions?

Gears are wheels with teeth around the edge that mesh with another gear to transfer mechanical energy. They offer a gear reduction in many motorized equipment. They are essential for effectively and seamlessly transferring power, torque, force, and motion from one shaft to another.

Gears are usually mounted or connected to other components via a base or shaft, and they are defined by two terms—teeth and radius. Teeth are the part of the gear that connects to another gear, while radius is defined differently depending on the side of the gear you are talking about. Radius typically refers to the distance between the center of the gear to the outside of the teeth or the base of the teeth.

This article will explain different types of gears and their functions. By the end, you will know the types and names of gears and how they work.

What are the different types of Gears?

There are several types of gears, depending on their design principles and characteristics. Spur gears, worm drive gears, bevel gears, rack and pinion gears, spiral bevel gears, helical gears, screw gears, miter gears, hypoid gears, and herringbone gears are the most common type of gears.

Spur gears

Spur gears belong to the parallel gear shaft group with a straight and parallel tooth line. They are one of the most commonly used gears that are easy to produce and can achieve high efficiency.

However, these gears are noisier than helical gears because they connect and transmit power to the axle with a single line of teeth. When in operation, a single tooth on the mesh rolls off of contact and accelerates to contact with the next tooth, creating an imbalance and noisy experience.

Helical gears 

This type of gear is used with parallel shafts, just like spur gears, and they have a cone shape with winding tooth lines. And, they have better mating gears than spur gears and do not make noise or vibration during operation, making them suitable for high-speed applications.

Helical double gears

Double helical gear is a type of helical gear with two surfaces facing each other with a space that separates them. They have similar designs with the single helical gear, but their directions are opposite to each other. Their double gears make them able to carry more thrust load and have a smoother operation than the single helical gear. Like the single helical gear, double helical gears are used in an enclosed gear drive.

Bevel gears

This type of gear has a cone shape with teeth around the cone and is used to transmit motion or power between two intersecting gears. They intersect at a 90-degree angle, and, as a result, they transmit less torque than parallel shaft gears.

Spiral bevel gears, helical bevel gears, straight bevel gears, zero bevel gears, crown gears, angular bevel gears, hypoid bevel gears, and miter gears are all kinds of bevel gears.

Screw gears

Screw gears, often referred to as crossed helical gears, are pair of helical gears used in transmitting motion between non-intersecting, non-parallel shafts. They have low capacity in carrying loads and are not recommended for large torque, power, or motion transmission because their tooth contact is a point. In simpler terms, they transmit power by sliding their tooth surfaces.

Spiral bevel gear

These are bevel gears that feature curved lines. They have a higher tooth-contact ratio, making them more outstanding than straight bevel gears in terms of strength, efficiency, noise, and vibration.

However, they are challenging to forge because the teeth are curved and costlier than straight bevel gears. They also cause thrust forces in the axial direction because the teeth are curves. Any spiral bevel gear that twists at a zero-degree angle is known as zero bevel gear.

Worn gears

The worn gear consists of two components—the shaft and the mating gear. The shaft has a screw that looks like a drill and does not intersect with the mating gear. They do not make noise or cause vibration when transmitting motion because there is a limited friction between them. Even though they transmit motion quietly and smoothly, they are not the most effective gears. They are mostly used in agricultural equipment.

A worm gear is a screw-shaped cut into a round bar, and a worm wheel is a gear that meshes with the wheel at a 90-degree shaft angle.

Miter gear

A miter gear is a type of bevel gear that transmits rotation between two shafts that intersect at a right angle. Miter gears are often used as right-angle drives, that transmit force between intersecting shafts at a 1:1 ratio.

The gears are engineered with precision and are used in a place that requires high efficiency. A miter gear cannot work together with another mitre gear unless they have the same number of teeth, pitch, and pressure angle. However, the gears do not have the ability to increase or decrease speed because they only work with another gear of the same number of teeth. Their primary purpose is to offer a change in the transmission direction.

Internal gears

Internal gears have teeth inside of a cylinder or cone and are usually paired with gears having teeth on the outside. They are mostly used for gear-type shaft coupling and planetary drive gears. When in operation, the internal and external gears rotate in the same direction, whereas two external gears rotate in opposite directions.

Because the gear teeth are on the inside, they cannot be manufactured with the usual hobbing machine used in producing spur gears. Instead, they are produced with a gear-shaping machine or gear-shaper.

Rack and pinion gear

This type of gear are made of two different gears—rack and pinion. The pinion is the cylindrical gear that sits upon a straight gear. Rack, on the other hand, is the straight gear. They are mainly used in the steering mechanism of vehicles. Rack and pinions are also used in lifting mechanisms, horizontal movement, and positioning mechanisms.

Herringbone gears

A herringbone gear is similar to a double helical gear with the differences being that there’s no space between the two faces and it is shorter. While the herringbone gears operate quietly and smoothly at higher speeds, they are difficult and require lots of money to manufacture, meaning they are not widely used.

Hypoid gears

Hypoid gear is a type of spiral bevel gear that transmits motion between two shafts at right angles. Unlike other bevel gears, the hypoid gear does not intersect. They are mainly used in rear-drive drivetrains and differential gear units. 

Straight bevel gears

A straight bevel gear is a gear with a cone shape that transmits motion or power from one intersecting shaft to the other. Unlike other bevel gears, the teeth of a straight bevel gear are designed in a straight line that intersects between two shafts. Also, the outer part of the straight bevel gear tooth is larger than the inner part.

Final Words

You have seen several types of gears. Each of these gears serves a unique purpose. The spur gears are simpler than other gears like bevel, helical, and worm drive gears. However, it does not mean you can use spur gears in place of others because of its simplicity.  All gears, whether simple or not, serve one purpose—enabling efficient transfer of power and motion.