A hex flange nut is a fastener that incorporates both a hexagonal nut with a flanged or washer-like base, which is a wide area on the bottom of the nut that extends outward past the typical diameter of the nut. Used when a flat washer is not practical, a hex flange nut allows the pressure of the nut to be displaced over a wider area than a plain nut would allow. Most hex flange nut designs are used in locking-type applications, with the flange nut using either a serrated back on the flange or a locking thread within the nut itself to lock the fastener into position when tight.
Often used when a separate locking nut and washer would be difficult to employ, the hex flange nut allows the user to start the fastener with one hand even when in a difficult location to access. Once started, the hex flange nut is easily tightened into place using a socket wrench and an air tool. Most assembly line manufacturing jobs enlist the aid of hex flange nuts to speed the assembly process along the line. Workers are much faster placing a single fastener onto a bolt or stud than compared to placing a locking washer and a nut onto a comparable bolt or stud. This makes the line run smoother and requires less stops due to missed fasteners or cross-threaded fasteners, which are nuts that are forced crookedly onto bolts as a worker rushes to stay caught up with the assembly line.
The flange nuts are available in most common metal types including brass, stainless steel and titanium. Course and fine thread nuts are also available in the flanged design, making the fastener a viable option for most fastening requirements. The serrated bottom of the locking flange nut design is a popular choice with electronics fasteners. The serrated flange bites and holds electrical fasteners in place. When used on a fragile surface, such as aluminum, the flanged nut is much less prone to damaging the soft metal surface than a traditional nut.
Another popular reason for using a hex flange nut is the ability to place the nut into a socket wrench and then reach into hard-to-access areas without dropping the nut. The flange sits tightly against the edge of the socket wrench and prohibits the nut from sinking deeply into the socket. The socket can be used as an extension of the user's arm in order to start the nut onto the bolt. Combined with a magnetic socket wrench, a hex flange nut is nearly impossible to drop out of a socket wrench.