Captive Fasteners and their common types
Captive fasteners are a specialized fastener type, capable of achieving a permanent hold of an assembly even during servicing procedures. Captive fasteners can create a hold through a number of methods, taking advantage of thread locking, press-fitting, or broaching for ample security. Additionally, some captive fasteners may even meld with the material they are joined to if welding or cold forming is carried out. To best understand how captive fasteners can be beneficial for various applications, we will discuss some of the most common types that may be used for installations.
Captive Nuts
Captive nuts are fairly similar to standard types, featuring internal threading that allows them to be joined with a correlating threaded fastener. Unlike conventional nuts, however, the captive nut features a spring steel cage that encapsulates the fastener. With their ability to mate with studs, captive nuts prove effective in securing items in blind locations while minimizing damage to any surfaces. Captive nuts are fairly simple to replace, and they can benefit materials that are too soft to accommodate other fastener types. Generally, captive nuts find common use in industrial and electronic applications, often being relied on for the mounting of equipment in square-holed racks.
Weld Nuts
Unlike captive nuts that are tightened onto an assembly, the weld nut is a fastener which is welded to another component. Constructed from either stainless steel or low carbon steel, various types of weld nuts exist to accommodate the needs of different applications. Retainer weld nuts are a type that feature a floating nut placed within a retainer, allowing for off-center or misaligned screws to be added to the assembly. Meanwhile, single tab weld nuts are those that facilitate the requirements of heavier gauge materials. With other weld nuts such as twin pilot types, slab base types, and four projection types, many applications can benefit from their use.
Pallet Nuts
Pallet nuts, also commonly referred to as tee nuts or knock-in nuts, are a type that are commonly constructed from metal or plastic. With a large flange fitted with teeth that are manually hammered in by an operator, the teeth can dig into a pallet material in order to retain the positioning of the fastener with security. Pallet fasteners are often used for a variety of construction operations, benefiting wood surfaces that need to be secured.
Captive Screws
For PCB assemblies and various equipment panel constructions, captive screws are an optimal fastener choice. Such screws are recognizable for their unthreaded shank and threaded tail-end, allowing for them to be locked into pre-drilled holes. With this method of attachment, the screw may be installed and removed without having to detach the entire assembly. Captive screws are often paired with a number of components for the creation of a self-captivating assembly, these elements including retainers, washers, and springs. Generally, captive screws are used when an assembly is faced with environmental stresses such as vibration, thermal conductivity, or thermal expansion. With captive screws, fastening solutions can be provided for signs, medical devices, networking cabinets, electronic enclosures, and much more.
Captive Pins
Captive pins are a fastener type that may be pushed into an assembly in a similar fashion to rivets, and they feature self-clinching heads that can deform mating materials that are softer than the fastener itself. As the heads are quite robust, they can resist push-out forces and torque that seek to loosen their hold. Generally, captive pins may be used for applications related to electronic circuit boards.
Captive Standoffs
Captive standoffs are internally threaded, capable of securing, supporting, and creating space for various assemblies with the help of other fastener types. Oftentimes, captive standoffs are useful for mourning circuit boards and various components to a chassis.
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