Design Considerations for Flanged Nuts & Flanged Screws

Flanged Nuts  

Definition

A standard nut is a small, hexagonal-shaped mechanical component with a threaded hole that fits on a bolt or screw. The nut provides the primary clamping force to keep structural joints together. To put it simply, flanged nuts look just like standard nuts except they have a large flange on the bottom where the flanged nut meets the mating joint. Flanged nuts are designed for the key purpose of providing an additional clamping area to joints by basically expanding the footprint of the nut on the underside of the clamped joint. The flanged portion of the nut is the main clamping interface on the joint while the other side of the nut, like traditional nuts, is the access point to tighten or loosen the joint using a wrench.

Pros/Cons

The most obvious advantage of a flanged nut lies in the fact that the component is basically an integrated flanged nut and washer, incorporating both into a single part and reducing the number of components required for machine design and assembly. However, the biggest functional benefits of the flanged nut are the superior clamping force provided to the joint and the fact that locking features, such as serrated flanges, can be incorporated directly into the nut to maximize joint stability. Flanged nuts lend themselves to applications with oversized holes due to the fact that the flange washer increases the mating surface contact area. One notable drawback of the flanged nut is that in certain situations they can be more difficult to physically grasp with pliers for untightening or removal activities.

ProsCons
Superior clamping forceDifficult to grasp with pliers
Reduced number of components (no washer needed) 

Application Examples

Flanged nuts are widely used within applications that experience high vibrations. These applications would typically employ a flanged nut with a serrated locking mechanism to provide additional clamping force and locking during the entire life of the mechanism. The most consumer-facing application high vibration applications where flanged can be found is likely landscaping equipment such as lawn mowers. The flange on the nut acts to distribute the torque pressure making it less likely that the joint becomes loosened over the life of the equipment.

Flanged Screws

Definition

Similar to flanged nuts, flanged screws are essentially screws with an integrated washer under the drive head. Flanged screws are typical normal screws that have an extended, flat area under the drive head. The flat head on the screw expands the surface area under contact on the screw side of the joint, distributing the load across a bigger surface area on the joint. This is a critical function because fasteners affix large clamping forces into the surfaces of the joints depending on the preload.

Pros/Cons

Many of the same benefits of flanged nuts such as clamping force, locking features, and reduced component counts hold true for flanged screws. The flanged screw also has the benefit of potentially reducing the corrosion potential of the joint because separate screw/washer components can be subjected to corrosion concerns if corrosive mediums become trapped between the screw and the joint material. One notable drawback of flanged screws is that these screws have unique geometries compared to traditional bolts and screws, and as such, they probably won’t fit other generic fastener applications given the fact that they have a larger footprint on the screw head on flanged screws.

ProsCons
Superior clamping forceUnique geometries
Locking feature 
Reduced corrosion potential 
Reduced number of components (no washer needed) 

Application Examples

Flanged screws are used in many of the same overlapping applications as flanged nuts. The most common applications for flanged screws are those that have components that must fit together tightly to contain liquids or gases such as pressure vessels, or piping applications. The most common example would probably be automotive exhaust components. Electronic products also used flanged screws because these applications are typically small and must be easily put together and/or disassembled for troubleshooting purposes.

In Closing

This whirlwind survey of flanged nuts and flanged fasteners has hopefully motivated you to learn more about how these unique fasteners may be beneficial to your machine design application. To serve you to this end, MISUMI has a wide assortment of flanged nuts and screws to choose from. Explore them all here.

About the Author

Carlicia Layosa

Carlicia is a Product Marketing Engineer at MISUMI. She holds a bachelor's degree in Mechanical Engineering and a master's degree in Energy Engineering from the University of Illinois at Chicago. She is a Certified SOLIDWORKS Associate, Marketo Certified Expert, and is passionate about education and training.

One thought on “Design Considerations for Flanged Nuts & Flanged Screws

  1. As someone who works with aluminum parts, I would add that another con of flanged hardware is that it can lead to marring / scuffing of the part you’re screwing into when compared to using a non-flanged nut or screw with a flat washer, which usually will protect the underlying surface thanks to its free rotation. Without a freely rotating washer, the act of torquing down the screw causes its head to rub the surface, leaving telltale circular marks on the parts.

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