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Types of Gears: A Guide on Different Mechanical Gears

Gears are used for the transmission of the rotation around an axis in machines. They control the speed of the motor with the help of rotations. So they can be used to speed up the motor as well as slow it down. Gears can be found in clocks, bicycles, wheelchairs, and washing machines, to name a few everyday items. 

The gears are designed with metallic or high-density plastic wheels with teeth around the circumference. These teeth move or rotate on an axe mesh to create motion. As a result, both the connected axes move in the intended direction. Gears come in different types, including spur, bevel, and worm gears. We will discuss different types of gear in detail. 

Importance of Gears and How They Work

Gears work for mechanical transmission when a force is applied to create an output. This happens with the change in torque and speed of the machinery. Gears are added in high-load machines to ensure easy movement and reduce speed as needed.

In addition, gears can be used to reduce/control the speed of the motor. Therefore, it works better than a pulley system to stop the machine. The fine control provided due to gear teeth can also transfer the motion to nonparallel axes. 

Monochrome image of a complex array of metal gears and cogs within industrial machinery, highlighting mechanical functionality

Using gears, you can increase your speed by applying more speed. On the other hand, you can decrease your speed by applying less force or force in the opposite direction. 

A gearbox is also essential to increase the torque of the machinery. This changes the direction of the motion as needed. The increase/decrease in torque is carried from the driving motor to the driven equipment via a rotation shaft.

A system of gears can be used to produce large amounts of force, resulting in high speed. The clockwise and anticlockwise motion of the gear teeth will decide if the speed increases or decreases. The teeth move smoothly over the shaft to transmit the force from one axis to another. Besides, the type and size of the gear will also impact the force. 

Understanding Different Parts of Gears

The following terms will help in understanding the different parts of the gear and how they function together.

Detailed close-up of mechanical watch gears with brass elements and ruby jewel bearings, emphasizing precision engineering

Axis: The shaft of the gear passes through the center of the axis. Moreover, the axis of the gear may be intersecting, non-parallel, or parallel. The gears with intersecting axes pass through a common point. Non-parallel or nonintersecting gears have axes in different planes. Parallel axes rotate in different directions and do not intersect at any point. 

Twist Direction: The gears are either right-handed or left-handed, depending on the position. This direction depends on the shape of the spring. In the case of two helical gears, the teeth move in the same direction on one side. On the flip side, the bevel gears have different twist directions that are opposite to one another. 

Teeth: The teeth on the gear are jagged protrusions that are on the circumference of the circular or semi-circular shape. They stick out and move on the teeth mesh to transmit the rotation motion. Ideally, the number of teeth must be a whole number. 

Moreover, the profile of the gear teeth and teeth mesh must be the same for them to move smoothly and work. The gear speed is calculated by dividing the number of teeth of the input gear by the number of teeth of the output gear. This ratio is also called the gear ratio. 

Pitch Circle: The pitch circle is calculated with the tangent that passes from the mesh of the two gears. Besides, the perimeter of two overlapping gears provides the size of the gear as they perform as a singular unit. 

Pitch Diameter: It is the gear’s working diameter and is also called a pitch circle. It dictates the distance between the two gears in a machine. The distance between the two axes will be the sum of the two-gear pitch diameters divided by 2. 

Diametral Pitch: It is the ratio of the total number of teeth and the pitch diameter. 

Circular Pitch: The circular pitch is calculated using the distance from one tooth’s point to the adjacent tooth’s point. Since the length is in arc form instead of a straight length, it gives the pitch circle length. 

Module: The module is the size of the tooth in millimeters. It is calculated by dividing the pitch diameter by the total number of teeth. It will always be a rational number to ensure reliable industrial application.  

Pressure Angle: The angle between the radius of the pitch circle line and the tangent line to the tooth is the pressure angle. Some standard angles of 14.5, 15, 20, and 25 degrees are used for gears. The most used one among these is 20 degrees. 

The large pressure angle shows a wide dedendum, ensuring a high tooth strength. Note that the pressure angle is calculated via the distribution of force and the contact of teeth. Therefore, the two gears should be designed in such a way as to ensure the same pressure angle to the mesh.

Gear Shape: Different gear shapes may include circular, semi-circular, triangle, square, and elliptical. These shapes impact the speed and torque of the machine. A uniform shape of the gear, such as circular or elliptical, will result in the same speed and torque. On the other hand, the non-uniform gears may produce different speeds and torque depending on the position of the teeth, even when the input is the same.

Torsion Angle: This is the inclination of the tooth to the machine’s cylindrical axis. The thrust direction increases as the torsion angle of the gear increases. Due to this, the machine’s efficiency may decrease. The usual torsion angle is 25 degrees to manage the machine’s efficiency and thrust. 

Different Types of Gears

Colorful assortment of interlocking gears with motivational words, symbolizing teamwork and progress in mechanical design

We have compiled a list of different gear types.

Gear Type Main FeaturesApplications 
Spur GearsCircular gear, easy to manufacture and most commonAutomobiles, speed reducers, clocks
Bevel GearsIntersecting axes with conical gears Water pump systems, power plants, cooling towers, crusher machines, 
Helical GearsSingle/double helical gears, low noise and friction, smooth transmissionconveyor belts, elevators, vehicles
Rack and PinionDifferent shapes connected together, and transmission speedPrinting machines, mechanical carriers, lifts
Planetary GearboxesSun and planet gears that cause transmission simultaneously, great for heavy loads Automobiles, aircraft, and helicopters
Worm GearsGears with non-intersections/non-parallel axes configuration, high gradual torque Rolling mills, engines, and lifts
Cage-Peg GearsRotation transmission in perpendicular axes, multidirectional useWatermills 
Mutilated Gears Reduced teeth in gearManufacturing machines, speed reducers
Non-Circular GearsDifferent shapes connected together and transmission speedPumps, conveyor belts, potentiometers

Spur Gears

These are the simplest and most popular gear types. They transfer motion between parallel shafts. Their straight teeth make them easily manufacturable with 3-axis machines like laser cutters or injection molding.

When two spur gears are used, they are placed adjacent to each other on the mesh, enabling spinning motion in the opposite direction. The transmission of power via a group of spur gears works in a parallel shaft. They are commonly used in gear pumps, motors, conveyor systems, and speed reducers.

Bevel Gears

Bevel gears transmit power between non-parallel axes. When the slanted teeth meet at the same vertex, they form miter gears at 90-degree angles. The slanted teeth make pitch diameters in the shape of a cone. 

Thus, the gears are differentiated based on the distance b/w the rear of the gear and the tip of the cone of the gear. To mesh two bevel gears, the imaginary cone should extend to the same vertex. These gears are expensive to form due to the intricate design. Moreover, they transmit large torque, so they are not always the first choice for machinery. 

Types of Bevel Gears

Bevel gears come in various designs, such as straight, spiral, miter, and crown. Straight bevels are easy to manufacture due to their simple design. The teeth in straight bevel work simultaneously. Thus, the teeth are gradually tapered to ensure the pitch surface has a conical shape. 

In spiral gears, the teeth have curved lines to maintain a good contact ratio. They are more efficient than the straight bevel gears. Besides, they do not generate high vibration and noise. 

Zerol bevel gears are known to have features of straight as well as sprial design. They are trademarked design by Gleason Co. These gears are designed in such a way that teeth can rotate freely in any direction. The zero twisting angle makes it easier for them to move like this. 

Another bevel gear is a miter with a 90-degree shaft, which can transmit power change despite no impact on the speed. Lastly, crown gears/face gears are designed at the right angles. They are used in printing presses, railways, automobiles, power plants, and marine applications.

Helical Gears 

With angularly positioned teeth, helical gears have a non-parallel slanted tooth trace. Due to multiple teeth in transmission, helical gears are good for carrying heavy loads. Also, they make less noise as there is minimal vibration and friction during transmission. 

You can choose from various types of helical gears– single, double or herringbone. Single gears have either a left-hand or right-hand helix. Double gears have two identical helical faces in opposite directions. Using double gear helps in better transmission due to higher efficiency and lower friction. 

Another type is the herringbone gear, where two gears are joined without any spaces in between. These are great for shock absorption in machines. 

Rack and Pinion

This gear mechanism converts linear motion to rotational motion or vice versa. So, it’s ideal for applications like steering systems. They are present in pairs with two circular gears. Conventionally, straight or helical gears make up rack and pinion gears. 

The rack and pinion gear work with a pinion/spur gear and a tooth rail to cause the movement. There is a continuous sliding motion leading to the gear rotation. They are used in automobiles’ steering systems.

Planetary Gearboxes

As the name suggests, planetary gearboxes have internal gears called sun and planets. The sun is in the middle of the gearbox, and it rotates other planets. This movement causes the large internal gear to move and cause motion in the machine. 

Appropriate lubrication is necessary to ensure all the gears move smoothly. Planetary gearboxes are efficient enough for large force requirements. They may also help in large gear reductions when the space is limited. 

Worm Gears

Worm gears are driven by a screw on the shaft, called the worm, and the mating gear called the worm wheel. The gear rotates on a different plane perpendicular to the worm. Each rotation of the worm makes the gear rotate one tooth. 

This implies the gear ratio here is N:1, N being the number of teeth in the gear. Worm gears tend to be less efficient in speed, but they can gradually increase the torque in the system. 

There is a non-intersecting transmission with a sliding contact. The movement is smooth due to less friction. So these gears are not noisy. Another design element to note is that worm gears are linear instead of common circular designs. 

Cage-Peg Gears

Cage-peg gears are usually fashioned with wooden materials and dowels. They are easier and cheaper to make than their metallic counterparts. These gears transmit force into the perpendicular axis and, hence, do not offer much speed. A cage can act like different gears, such as worm gear with dowels and teeth. 

The pegs in these gears work as teeth that are connected to a small disc. These pegs connect with other pegs from different gear to work as a unit. One benefit of cage and peg gear is that it can work from either end as the pegs move in both directions. 

Mutilated Gears 

Some machine designs may call for mutilated gears where the tooth does not extend completely around the pitch circle. If the full 360-degree rotation does not occur, mutilated gears with a lesser number of teeth can be added. 

This is ideal when the machinery is not required to move continuously. The presence of teeth on one side of the gear and the empty side on the other side will lead to pulses of motion, making the shaft work at consistent breaks.

Non-Circular Gears

The fascinating thing about non-circular gears is their interesting shape. Their diameter is not the same in all areas. So, when they rotate, the shape of the gear changes, leading to different rotating speeds at all times. These are rarely used but may add to unique machine functions where two axes need a non-circular gear. 

Designing Considerations for Gears

Here are some essential things to consider when designing gears: 


The dimension of the machinery is a deciding factor for space available for the gears. Keep in mind the space to accommodate multiple gears, teeth, and shafts. Moreover, the gears should be able to move around the pitch circle. 

Exquisite pocket watch movement showcasing intricate gears and 19 jewels, with detailed engravings and golden accents

If there is a size limitation, smaller gears or non-circular gears may be used. Another option is to use mutilated gears. Pay attention to the pressure angle, pitch, and tensile strength of the manufacturing material.

The design requirements also include following the international and national design standards of manufacturing. For instance, you may follow American Gear Manufacturing Standards to ensure safe design and manufacturing. These protocols may also depend on the geographical location and be different in the US, Germany, and Japan.  

Operational Conditions

Environmental conditions like temperature, weather conditions, and humidity may have an impact on the gears. The lubrication and friction between the teeth and gear may be reduced due to harsh weather conditions. So, consider these when adding finishing touches and surface treatments to the material at the end. 

Manufacturing Cost

Consider the cost of manufacturing the gears. It may depend on the process, such as CAD designing, CNC lathe machining, or injection molding. Make sure the manufacturing process meets the regulatory requirements. Include the cost of raw materials and finishing touches to get the right estimate. 

Note that the price of custom gear designs will be higher. If you’re partnering with a manufacturing company ask for bulk order quotes even for bespoke designs. 

Transmission of Motion

The motion of the gear teeth must be considered in the design components. Gear transmission includes torque, friction, and force applied in different axes. The different shapes of gears, such as helical and non-circular gears, impact the direction and impact of the system’s speed. 

Wrapping Up

Now you know all about common gear types. The most commonly used types are spur and bevel gears. They are used in automobiles, conveyor belts, and clocks. Some gears like rack and pinion and planetary gearboxes are efficient; thus, they are used for heavy machines. 

The best gear for a system can be determined by considering the functions and materials. Once the CAD design is finalized, the CNC manufacturing process will ensure precision. Partner with  HiTop Industrial designing and CNC professionals to produce high-quality gear.

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