A jaw coupling is a kind of general purpose power transmission coupling that also can be utilized in motion control (servo) applications. It really is made to transmit torque (by connecting two shafts) while damping program vibrations and accommodating misalignment, which protects other elements from damage.
Jaw Couplings are one of the first and still most widely used elastomer couplings in the globe due to their inherent simplicity. Two similar hubs with 3 face lugs are connected through a star shaped element, sometimes referred to as an insert or spider. The 3 piece design makes them easy to work with and popular on applications such as pumps, followers, blowers and compressors.
Jaw Couplings need no lubrication and provide high reliability for light to moderate duty applications with good alignment of equipment and no requirement 
for torsional dampening.
In normal operating conditions there is no metal to metal contact so the life of the hubs is virtually indefinite. Nevertheless, in a catastrophic failing of the component the load would be carried by the hubs offering a degree of failure safety. Jaw couplings are resistant to oil, dirt, wetness and grease.
Specific element materials are available to achieve maximum performance for the functioning conditions.
The standard element materials is NBR (N)-‘Synthetic Rubber’. It really is highly flexible, essential oil resistant and the torsionally softest of the element options. It has a temperatures operating range ideal for most commercial applications and allows for up to at least one 1 degree misalignment capacity of the linked shafts. NBR is the most economically costed option.