Couplings are simply used to enable a motor to turn a lead screw, or other type of shaft. There are two types of couplings, rigid (one piece), and flexible (an assembly of pieces). Flexible couplings are composed of two hubs and a central spider. One hub is fastened to a motor shaft with a set screw. The other hub is fastened to the lead screw end. The rubber spider enables the two hubs to connect and turn while still allowing for a bit of flexibility in alignment and angle. Below, you will find rigid couplings and coupling sets that include two hubs and one spider for common uses, and you can purchase coupling hubs and spiders separately.