Mechanical Basics

What Is A Gear?

Gear is a circular mechanical device or a part that consists of the tooth that helps to transmit the required or definite velocity ratio whenever the distance between the driver shaft and the driven shaft is less. It is used to transfer the low speeds and at the same time high speeds too. The speed transmission depends upon the types of gear and its size.

What can you learn from this post?

  • Why Gears Are Used?
  • Terms Used In Gear
  • Types Of Gear Materials
  • Types Of Gear
  • Advantages Of Types of Gear
    • Advantages Of Spur Gears
    • Advantages Of Helical Gear
    • Advantages Of Bevel Gear
    • Advantages Of Worm Gear
  • Applications Of Types of Gear
    • Applications Of Spur Gear
    • Applications Of Helical Gear
    • Applications Of Bevel Gear
    • Applications Of Worm Gear
  • Conclusion

Why Gears Are Used?

The main aim of a machine is doing some work with the help of links, linkages, devices, and parts; energy transmission is the main objective to achieve it. Transmitting energy alone is not only an important aspect; in addition to this, channeling the energy with a definite velocity ratio are the crucial roles of gear.

So when the distance between the driver and driven is less, then Gear plays a crucial role in carrying the energy with the required velocity ratio. Let us try to learn what is a gear? And terms used in gear, materials used for gear, and different types of gear.

Terms used in gear:

Designing a gear depends upon the velocity ratio required to transfer the energy from the driver to the driven, so there will be terms that will help to design the gear which nothing but the designing of the tooth. To study the terms used in gear we have to zoom to the tooth of the gear. So, some of the important terms used in Gear are as follows.

What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear


                  Gear Tooth and its Nomenclature

We need to draw the imaginary lines, curves with respect to the tooth of a gear to understand the terms clearly.

Pitch circle- The pitch circle is an imaginary circle that can draw by tracing the meshing points when two gears rotate without any slip. The diameter of the pitch circle is also as called as Pitch Circle Diameter. (Observe Figure above: Gear Tooth and its Nomenclature).

Addendum– The addendum is the radial distance that can measure from the pitch circle to the top of a tooth. (Observe Figure above: Gear Teeth and its Nomenclature)

Dedendum– The dedendum is the radial distance that can measure from the pitch circle to the bottom of a tooth.  (Observe Figure above: Gear Teeth and its Nomenclature)

The angle of obliquity (Pressure Angle) – The Angle of obliquity or the pressure angle is the angle that can be measure between a normal and common tangent at the tooth pitch point when two gears are in contact. It usually lies between and .

Circular pitch– The Circular Pitch is the distance that can measure on the pitch circle from a point on the tooth to the same point on the next tooth of a gear.

Diametrical pitch-The diametrical pitch is the ratio of the number of the tooth to the diameter of the pitch circle in gear.

Module– The module is defined as the ratio of the diameter of the pitch circle to the number of the tooth in a gear. (Or) It can be explained that the module is quite reverse to the diametrical pitch.

So, these are the few terms that are commonly use in the gear nomenclature.

Types Of Gear Materials

As we know that the gear is used to transfer the energy from the driver to the driven and they will work at high speeds. So, to withstand at such high speeds; a gear should acquire high strength and should be wearresistant.

The materials used for gears are metallic and non-metallic in construction, but the usage is same. According to their application, the material of the gear will be finalized.

If we talk about metallic gear, the cast iron (you can read about cast iron in detail) is the material that is widely used to manufacture the gear. It possesses high strength, high wear resistance, easy to mold, and easy to machine. Other than cast iron, steel will be the option for manufacturing the gears. It too acquires high strength according to its heat-treatment process.

Non-metallic materials that gears are manufactured by

  • Rubber
  • Plastic
  • Micarta
  • Textolite, etc.

Types Of Gear:

The gears are used to transfer the rotating motion from the driver to the driven in the machines. So, sometimes it is required to transfer the energy from different angles. So, there are different types of gear according to their construction and tooth design. Now, we will differentiate the types of gear according to their Tooth Design and Application. They are

Spur Gear- Spur Gear is one of the types of gear and most widely used gear type. We can differentiate it by the design of its teeth. If we once observe the below image, the teeth of the gear are parallel to the center of the axis of the gear. So such gears are said to be Spur Gears.

There are two types of spur gears, Internal Spur Gear and External Spur Gear.

What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear

External Spur Gear

The Internal Spur Gears are those which consist of teeth on the outer side and the mating of the gear teeth takes place on the outer surface (shown in the Figure-External Spur Gear).
What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear
The External Spur Gears are those which consist of teeth on the inner side and the mating of the two gears teeth takes place on the inner side (shown in Figure-Internal Spur Gear).

The Spur Gears are simple in construction and used in low and medium speed applications. They produce or transfer high power.

Helical Gear- The Helical Gear is also an important and widely used types of gear in transforming energy but if we observe the design of it, the teeth are designed and manufactured with some angle whereas the spur gears are straight and parallel to the axis.

What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear


    Helical Gear

Helical Gears are intricate in construction but due to their tooth design they are used at high speeds and they can withstand high loads too.

Bevel Gear- Bevel Gears are the pair of gears that the teeth are designed on one of the sides of a cylindrical part. The two gears are called Gear and Pinion.

What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear          Bevel Gear

The two gears are arranged perpendicular to each other to transfer the energy or power in a perpendicular direction (It means, one of the gears is connected to the Driver and another to the Driven where both are perpendicular to each other as shown in the figure)

Worm Gears:

What Is A Gear-Types Of Gear, Advantages, And Applications Of Gear           Worm Gear

Technically, this is a Worm Drive whereas a Worm will mesh on the Worm Gear to achieve the required transformation. In this, we can see that the worm is a circular and long shaft type part where the teeth are designed around it.

Till now we observed that the gear is a cylindrical part and teeth are designed on the outer or inner side of them but when it comes to the Worm Gear, it is quite different. The worm and worm wheel or gear have meshed in a way that their axes are perpendicular to each other.

The Worm wheel may be Spur Gear or a Helical Gear. The type of Worm Wheel depends upon its applications.

Advantages of Types of Gear:

If we look up the advantages of different types of gears, they are wide and nonignorable. It should be noted that the common advantages of every gear is to Transfer the power or energy from driver to driven or one shaft to another shaft. Let us see advantages of each types of gear precisely.

Advantages Of Spur Gears:

It is simple to construct.

  • Spur Gears are high Efficient compared to others.
  • Spur Gears are more Reliability and less chance of permanent failure.
  • Spur Gears are used at low and medium speeds with high power transmitting efficiency.
  • They are used in high loads transmission.

Advantages Of Helical Gear:

  • Helical Gears allow Non-noisy and smooth working conditions even at high speeds.
  • It produces less wear while working.
  • As the helical gears are helix-shaped, the meshing of teeth with another gear is large when compared to the other gear.
  • Helical Gears are used in the high-speed transmission system.
  • Helical Gears Produces a large amount of Thrust.

Advantages Of Bevel Gear:

  • Bevel Gears are used in the transmission of power when the driver and driven supposed to place in perpendicular positions.
  • The fluctuations in the speed can be balanced with the bevel gearing.
  • Bevel Gears are used at the differential drives, when there are speed fluctuations and un-similar power transformation then these bevel gears will help to balance the speed and power.

Advantages of Worm Gear:

  • Worm Gears are used to transfer the high torques.
  • Sometimes, it is impossible to achieve the required motion so worm gears will help to achieve so. For example Gear Boxes of Automobiles.

So, these are the advantages of types of gear. Now, let us see the applications of gears.

Applications of Types Gear in daily life:

Applications Of Spur Gear:

  • Spur Gears are used in all simple machines where the low and medium speeds should be transfer.
  • Spur Gears can be used in every Machine Tools.
  • Spur Gears were even used in Wrist Watches and Clocks.
  • Spur Gears plays an important and crucial role to transmit the power in Gear Boxes.

Applications Of Helical Gear:

  • Helical Gears used in Rolling Mills.
  • Helical Gears will be used in Steam and Gas Turbines due to their high-speed transformation.
  • The Helical Gears are used at places where high speed is necessary to transfer.

Applications Of Bevel Gear:

  • Bevel Gears are used in Automobile Differentials.
  • Bevel Gears Plays an important role in Shaper Machine Tool.

Applications Of Worm Gear:

  • Worm Gears used in the Gear Boxes.
  • Worm Gears even helpful to perform the tasks in the Music Instruments.
  • In the Lifts, the worm gear will be used.
  • Worm Gears plays important role in the machines for Speed Reducers.


Gears and types of gear are being most important part in our working life and their importance is being increased according to its applications too. Their usage is vast and uncountable. The different types of gears are evolved to overcome the difficulties of previous type. The Gear Designing is also a good learning course and do have a wide career opportunities. We study and learn the designing of the gear in the subject called Theory Of Machines.

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