Written by Dr. Jody Muelaner
Flat nuts are a simple nut that is stamped from sheet metal. They can be considered a type of speed nut, providing the functions of a sprung washer and a nut in a single component. They also have a degree of friction locking and they are extremely low profile.
Flat nuts include two raised tangs with curved ends engage with the threads of an inserted fastener. This style of interface can work with either a machine screw or a self-tapping fastener, though they’re typically designed for machine screws.
Because of their simple construction from sheet metal, with no formed threads, flat nuts are very low cost. Additionally, they tend to reduce assembly costs by allowing rapid assembly without requiring precise thread alignment.
Flat nuts are a type of self-threading nut, constructed from sheet metal — similar to lock-nuts, U-clips and J-nuts. The inherent spring in the tabs produces a friction locking effect. They enable rapid fastening because they’re simply held against the part while the fastener is inserted, without requiring precise alignment.
Typically, these components rectangular in shape with a gently arched profile and notched ends to the tabs. Many variants are available with options such as a round shape, diamond-shaped screw holes, the corners turned down, the ends turned up and no arch in the base.
The term flat nut is also sometimes used to refer to a jam nut, or half nut. This is a thinner version of a standard hex nut, designed to be tightened, or “jammed” against the primary nut. The two nuts together form a friction locking nut. The jam nut should be tightened first and the main nut then fitted over the top. A hex flat nut may also refer to a thin hex nut used to secure lightbulb holders.