How Does a Shaft Coupling Work?

A shaft coupling is a mechanical element that is designed to join two shafts together to accommodate for the misalignment of torque from one end to the other. In mechanical systems, couplings are considered a type of permanent or temporary connection between two rotating shafts that connect the driving and driven shafts together. In simplistic terms, couplings are utilized to connect input and output shafts in any power transmission system. For example, a gearbox shaft in machine tools is connected to the input engine shaft via couplings, or an engine shaft can be connected to a pump or compressor shaft through couplings.

Essentially, the function of a coupling is similar to that of a clutch. However, clutches are only temporary joints, whereas coupling joints can be permanent connections as well. In most cases, they are used to permanently connect two shafts. Keep in mind that shafts in power transmission do not always produce linear connections. In fact, they can be parallel, with intersecting axes and display slight eccentricity. As such, couplings are available in a wide range of types as per operational requirements.

Regardless of the type, all couplings have the same basic purpose: being installed in power transmission, joining misaligned shafts, reducing tremors and vibrations, and providing simple assembly and disassembly. The biggest difference among variations is the way that they are connected. Shafts can be connected in three ways, all of which are determined by the way they are aligned; thus, they can be in parallel, collinear, intersecting with some angular deflection.

Shaft couplings in particular, are used in motors, pumps, generators, and compressors as their most common application consists of a system that needs two rotating pieces of equipment to be connected for the means of transmitting power from one shaft to the other. Similar to other mechanical elements, shaft couplings are made in a variety of subtypes and styles to suit a myriad of applications, some of which we will cover below.

Beam Coupling

With single or multiple helical cuts in the coupling body, beam couplings can accommodate parallel misalignment up to 0.025 inches and angular misalignment up to 7 degrees. Moreover, zero backlash designs provide added positioning accuracy between the driving and drive shafts. Generally, beam couplings are made of aluminum alloys and stainless steel, but are also made in acetal, marring steel, and titanium versions.

Bellows Coupling

Especially suitable for speed control applications, bellows couplings consist of numerous convolutions of metal that provide high torsional stiffness, which is critical in positioning applications. Torsional stiffness reduces the level of angular and parallel misalignments a coupling can handle.

Chain Coupling

Made to handle power transmission applications, a chain coupling is used to transmit power in the hundreds of horsepower range. Meanwhile, it offers angular and parallel misalignment allowances at 2 degrees and 0.015 inches, respectively. It is worth noting that specialized types exist, those of which use special chain sprockets and double-wide roller chains with clearances that enable the design to operate as a flexible coupling.

Other Common Types:

  • Jaw coupling

  • Diaphragm coupling

  • Disc coupling

  • Gear coupling

  • Grid coupling


NSN Components is a leading supplier of shaft couplings in the industry as well as other top-quality items, including spool engine shafts, air compressors, drive shafts, and more. With over 2 billion new, used, obsolete, and hard-to-find options, customers can easily meet rigid time constraints and strict budget parameters. Kickoff the fulfillment process with a competitive quote on any featured item(s) and see how NSN Components can serve as your go-to parts purchasing partner!


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