A jaw coupling is a type of general purpose power transmission coupling that also can be used in movement control (servo) applications. It is designed to transmit torque (by connecting two shafts) while damping system vibrations and accommodating misalignment, which protects other parts from damage.
Jaw Couplings are one of the first and still hottest elastomer couplings in the globe due to their inherent simplicity. Two similar hubs with 3 encounter lugs are connected through a superstar shaped element, sometimes 
referred to as an put in or spider. The 3 piece style makes them simple to work with and popular on applications such as pumps, fans, blowers and compressors.
Jaw Couplings need no lubrication and offer high dependability for light to medium duty applications with great alignment of equipment no requirement for torsional dampening.
In regular operating conditions there is absolutely no metal to metallic contact so the life of the hubs is virtually indefinite. However, in a catastrophic failure of the element the load would still be carried by the hubs providing a amount of failure security. Jaw couplings are resistant to essential oil, dirt, dampness 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, oil resistant and the torsionally softest of the element options. It includes a temperature operating range suitable for most industrial applications and allows for up to at least one 1 degree misalignment capability of the connected shafts. NBR is the most economically costed option.