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What is a Flange Nut?

CW Deziel
CW Deziel

A flange nut is a nut that has that has one side shaped with a wide, flat surface. The surface, or flange, functions like a washer by preventing the nut from embedding in the surface being fastened when it is screwed onto the end of a bolt. It also distributes the holding power of the nut evenly over its surface to provide more secure fastening. Flange nuts are useful for attaching wood and metal parts and are widely used in carpentry, auto repair and industry. They are available in a wide range of sizes and materials.

The flange can have holes through which screws or other fasteners can be driven to hold the nut to the surface being fastened. Pre-attaching the flange to a surface provides a useful method of connecting something to it by means of a bolt or metal rod, which can be inserted into the stationary nut and tightened. The holes are also suitable for the insertion of glides, so machinery adjustments can be made by turning a threaded rod inserted into the flange nut.


Most flange nuts are hexagonal. The flange is sometimes serrated to give the nut better holding power. The serrations bite into the surface when the nut is tightened and are angled to prevent counterclockwise rotation that would result in the nut backing off and loosening. A hex flange nut may be made of hardened steel or titanium and coated with a zinc or chrome finish. If it is serrated, the hardened steel allows the serrations to bite into almost any material.

In order to prevent damage to the surfaces being joined, a flange nut can also have a swivel flange which functions much like a washer. A swivel flange remains stationary when the nut is turned, allowing more torque to be applied without danger of the flange scoring the surface or wearing it away. A swivel flange nut is most useful for joining wood and plastic.

A flange bolt is similar to a flange nut. It usually has a hexagonal head, and the the flange is attached to the base of the head. As with a flange nut, the flange acts like a washer, preventing the head of the bolt from embedding in the surface and providing extra holding power. Both flange bolts and flange nuts can have wings so they can be hand-tightened. A wing nut with a flange is useful for light-duty fastening applications.

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