A jaw coupling is a kind of general purpose power transmission coupling that also can be used in motion control (servo) applications. It is designed to transmit torque (by linking two shafts) while damping program vibrations and accommodating misalignment, which protects other elements from damage.
Jaw Couplings are among the first and even now most widely used elastomer couplings in the world because of their inherent simplicity. Two identical hubs with 3 face lugs are connected through a superstar shaped element, sometimes known as an put in or spider. The 3 piece style makes them simple to work with and well-known on applications such as pumps, fans, blowers and compressors.
Jaw Couplings require no lubrication and provide high reliability for light to medium duty applications with great alignment of equipment no requirement for torsional dampening.
In normal operating conditions there is no metal to metallic contact therefore the life of the hubs is practically indefinite. However, in a catastrophic failing of the component the load would be carried by the hubs providing a amount of failure security. Jaw couplings are resistant to essential oil, dirt, moisture and grease.
Specific element materials can be found to achieve 
optimum performance for the working conditions.
The standard element material is NBR (N)-‘Synthetic Rubber’. It is highly flexible, essential oil resistant and the torsionally softest of the element options. It has a temperature operating range ideal for most industrial applications and permits up to 1 1 degree misalignment capacity of the linked shafts. NBR is the most economically costed option.