The tiniest innovations are sometimes the ones that save the most time and energy in the industrial world. Coupling nuts are just such innovations. Also known as extension nuts, they function as threaded fasteners, joining together two threaded rods by joining them in between.
The outsides of coupling nuts are usually hexes, allowing them to be easily adjusted with wrenches. Coupling nuts in and of themselves provide an essential workpiece, though variations have been introduced that make coupling nuts even more useful. Reducing coupling nuts, for example, join two threaded rods of different sizes. Sight hole coupling nuts have peek-holes allowing the user to observe the amount of engagement. Some coupling nuts have left-handed threads allowing the user to create long rod assemblies from shorter rod lengths. In these cases, rods are threaded into the coupling nut only for a certain distance. Coupling nuts with both right- and left-handed threads are also available, allowing the user to screw in two rods at the same time by twisting the nut.
Coupling nuts can either be cold drawn or hot rolled, depending on the bar stock used.
Hot Rolled Steel
Often, before being rolled, steel is already above the recrystallization temperature from previous operations. The hot rolling process removes any induced stresses and grain deformation due to elevated working temperature. During the cooling process, non-uniformed cooling can occur, resulting in residual stress of the product.
Cold Drawn Steel
Cold drawing is performed at room temperature. Steel is first hammered and rolled so that it can fit through a die. A tool then turns the steel mass into wire. The room temperature steel is pulled through a die, reshaping it into the necessary shape. The process is similar to the flow of syrup that changes the syrup’s shape, but not volume.
Coupling nuts are used for a variety of applications. One popular use is for the attachment of knobs and handles. Plastic knobs and industrial handles with threaded rods can be attached to other threaded rods by means of a coupling nut, even if the two rods are not the same size.
Though they’re small and seemingly simple, coupling nuts have made a major impact on the industrial world. Take a closer look next time you’re around a machine or putting together your furniture. They’re much more prevalent than you might think!