Everything you need to know about Gear Couplings

Gear couplings are mechanical devices that provide a flexible connection to two rotating, non-collinear shafts by transmitting torque between them. The coupling type in any drive system is determined by the complexity of the connection, the field of operation, and the required torque transferability. Gear couplings are vital to many assemblies since they provide secure links to the system and stabilize dynamic vibrations that such connections may experience. Gear couplings may have one or two sleeves with two hubs of internal and external teeth conjoined as a continuous mechanical assembly. Couplings are the main components of aircraft turbines which are used to power aircraft pumps and motors. Since gear couplings are intrinsically fundamental to regular aircraft operations, learning more about their function and application is crucial.

Gear Coupling Design and Assembly

Gear couplings have rows of teeth lining the inner radius of their external hub and the corresponding outer radius of the internal sleeve, that of which connects in an interlocking mesh for securely attaching disparate shaft torques. Gear couplings can be rigid or flexible to amend any misalignment during connection. A misalignment can be caused as a result of a mismatch of the lateral axes of the connecting shafts in an angular, parallel, or a combination of radial and angular planes. The discrepancy in alignment can be 0.01-0.02 inches in the case of a parallel connection and 2 degrees in the case of an angular connection. Single mesh gear couplings are used to correct angular misalignments, while double mesh gear couplings are used for correcting parallel ones. Apart from the external hubs and internal sleeves, gear coupling designs also contain O-ring seals, drawn-off holes, and lubricating plugs. Gear couplings are securely installed using bolts, which may be exposed or covered through coupling guards of an appropriate size. Additionally, stainless steel is a popular metal used to construct these coupling types, although the inner sleeves containing the teeth can be made from nylon.

Several factors are considered while assembling gear couplings as they are more power-intensive when compared to other coupling types. Their lightweight, small size, and low overhung moment prove to be advantageous in high-power and high-speed applications with limited space. In addition, the metal-on-metal contact between the interlocking teeth of the gear coupling makes them unsuitable for high shock loads. However, due to their high torsional and bending stiffness, they are suitable for application in gas turbines which require a precise balancing of all components. Furthermore, the teeth should be sufficiently lubricated to function until the end of the maintenance period which will often last at least 12 months. More extended operational periods can warrant a change in the frequency of operation.

Types of Gear Couplings

Gear couplings are designed to suit different applications, and a few common types are described in detail below:

  • Flanged Gear Couplings

Flanged gear couplings feature collinear, face-to-face alignment of two flanges by placing one sleeve on each shaft, the assembly securely attached by multiple nuts and bolts.

  • Shear Pin Type Continuous Sleeve Gear Coupling

These gear couplings are designed to subdue excess torque or shock in equipment to which they are connected, thereby preventing any long-lasting damage. However, once the load on the equipment exceeds the predetermined standardized load specified by the customer, the coupling pin shears off, followed by an immediate disruption in connection.   

  • Floating Shaft Continuous Sleeve Gear Coupling

Floating shaft gear couplings are also called spacer couplings, and they are suitable for long-distance applications where both the load and the input drive are located at a distance. The floating shaft gear coupling is further divided into set-screw types, which are more traditional, and clamp-style couplings, which involve the shaft’s entire circumference. Floating shaft gear couplings are easy to install and do not cause damage while boasting immense holding power.

  • Flex-Rigid Gear Couplings

Flex-rigid couplings consist of one flexible and one rigid half, much as the name implies. These coupling types find application in floating shaft alignments to correct angular misalignments.


Complete Sourcing Solutions is the premier aircraft parts supplier in the civil and defense aviation sectors, featuring 15 distribution centers located throughout the United States and abroad. With our near-endless catalog of products, you can easily rely on us to source top-quality gear couplings or any other aircraft parts for your needs. Our expansive distribution network and easy-to-use directory will simplify your online parts purchasing process with your ability to conduct quick comparisons and narrow down searches with appropriate filters. Once you have zeroed down on your desired product, you can contact us through email or phone, or you can use the Instant RFQ service on our website so that a dedicated sales representative can reach out to you for further assistance with your order.


December 20, 2022

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