26 Jul, 2021

Know things about Gear Coupling

A coupling is a device used to connect two shafts. Their ends are connected to transmit power. The primary usage of coupling is to join two rotating pieces, with a degree of misalignment to allow movement at both ends.

Coupling falls into two categories, namely Mechanical and Material Flexing. The material flexible type obtains its flexibility from stretchable material like rubber which is resilient.

The material flexing coupling does not require any lubrication, grid coupling stands an exception. On the other hand, all the metal mechanical coupling does require lubrication.

Gear coupling belongs to the category of flexible coupling. They are used to transmit torque between two shafts that are not collinear. The coupling is made of two flexible joints – both fixed to each shaft. These joints are connected by a third shaft called the spindle. Gear coupling has a general misalignment of 4 to 5 degrees. They come in two variations – flanged sleeve and continuous sleeve.

  • Flanged Gear Coupling – It consists of short sleeves surrounded by a perpendicular flange. Each shaft has one sleeve placed on each shaft. In this way the two flanges line face-to-face. All the flanges are held with a series of screws or bolts.
  • Continuous Sleeve Gear Coupling – In this type of coupling, the shaft ends ate abutted against each other and then enveloped by a sleeve. These sleeves are generally made of metal, but the use of Nylon has also become quite common.

How To Calculate Gear Coupling Size?

Gear Coupling Size

To measure the gear coupling size, follow the below steps –

  • Calculate the inside diameter with a Digital Caliper.
  • Place the inside tips of the caliper inside the bowl.
  • Expand the caliper tips until they are fully extended to the bowl size.

These steps will give you the exact size of the bowl as needed.

Choosing a Gear Coupling

The most important factor in selecting a coupling is the torque rating i.e., the amount of torque that coupling can transmit. The torque can be controlled by increasing the service factor with the torque transmitted. Several other filling service factors are also taken into consideration such as –

  • Outside Diameter
  • Weight
  • Moment of inertia
  • Torsional deflection
  • Torsional stiffness

Working of gear coupling

Gear coupling transmits torque between shafts that are not collinear. In hoist mechanisms, the gear coupling connects the drive motor to the gearbox. It can also connect the gearbox using the flanged half directly to a smaller wire rope.

Coupling Service Factor

If the coupling is connected to the higher torque conditions, then the service factors are used. In API 671, an experience factor of 1.5 times normal torque is applied to take into consideration “off-design” conditions.

Grid Coupling

They are multi-piece mechanical shaft coupling and accommodate a slight variation in alignment between the shafts. The slight variation in alignment also absorbs the shock loads. They are used to transmit torque and rotation between shafts in mechanical power transmission assemblies.

Causes of Coupling Wear

Gear coupling teeth wear over time due to lack of fabrication, overloaded torque, misalignment, worn-out flange, or both, and thrust loading.

Flexible coupling

A flexible coupling is used to transmit power aka torque between shafts. This is done to compensate for minor misalignment. In a few cases, it also provides protection functions such as vibration dampening. It also acts as a “fuse” in case of torque overloads.

Function of coupling

The primary function of a coupling is to transmit power (torque). Some other function includes – accommodation of misalignment, and compensate of axial movement i.e., the end movement of shafts. In some cases, a coupling is also used to absorb shock or vibration.

TYRE Coupling

A tyre coupling also called elastic coupling consists of a flexible element like a tyre and two coupling halves, also known as hub or flange. Tyre coupling is flexible; thus they were used to compensate for significant angle errors and have a vibration effect.

Rigid and Flexible Coupling

  • The rigid coupling has rigid connections. Two shafts are firmly connected to allow a smooth transmission of torque throughout the system.
  • Flexible couplings have flexible connections. The components of flexible coupling lose some of the torque power through the interactions.

Shaft Coupling

A shaft coupling is a mechanical component connecting the drive shaft and driven shaft of the motor. This connection is done to transmit power. Shaft coupling brings mechanical flexibility and tolerance for shaft misalignment.


It is necessary to properly select, install and maintain the coupling. This will provide long life and good reliability. There are several advantages of gear coupling over other couplings, such as moderate misalignment. They provide exceptional stiffness and very high torque density.

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