Metal disc coupling is a type of flexible coupling that transmits torque through disc packs. Torque is transmitted by driving bolts pulling the driven bolts through a series of thin metal discs assembled in a pack. Disc couplings are torsionally rigid. Single disc pack (single flex) design can accommodate angular and axial misalignment, double flex design can also accommodate parallel misalignment. The torque density depends on the quantity of the bolts per disc pack. More bolts provide higher torque, but we have a trade off here. More bolts means less misalignment. Depending on application engineers have to pick the coupling that meets their requirement. If you can not find the perfect combination, maybe you should go one size larger or use another type of coupling. Disc packs usually come in 4, 6 and 8 bolt designs.