A shaft coupler are devices that connect two shafts to transmit power from the driveshaft to the driven shaft while absorbing some degrees of misalignments and mounting errors between the two shafts. Misalignments exist between two shafts as a result of the changes in temperature and deterioration of positioning accuracy over time. A shaft coupler provides mechanical flexibility to allow smooth rotation between the shafts and reduce impact, wear, vibration, noise, and risk of equipment failure.