Contemporary automotive designs call for reliable fasteners that allow quick initial assembly and ease of servicing in the field. Captive self-clinching fasteners meet these requirements and have been used in a variety of applications. Their uses are only limited to the imagination of the design engineers. Fastener selection is dependent on the characteristics of the material into which it is to be installed, such as:

• Composition (carbon steel, stainless steel, aluminium, fibreglass, etc)
• Hardness
• Thickness
• Strength, and

The elements to which it may be exposed, such as: Moisture Galvanic corrosion Solder Weld spatter Electrostatic discharge paint Electro-deposited primers/paint High vibration, and To applications in which the fasteners are used, such as: air bag assemblies, under hood accessories, brackets, interior trim, window regulators, truck roll-up doors, etc.

Air Bags

A popular application is in air bags, which have self-clinching dog-point studs mounting the air bag assembly to the steering wheel hub. The studs are permanently attached to the outer housing of the air bag mounting base, and are used to secure the air bag assembly in place with mating nuts. The dog point stud ends provide self-seeking threading, which assists the attachment of mating nuts when using high speed motorized nut drivers. The self-clinching studs meet the performance characteristics and assembly and servicing requirements needed for the air bag.

Under Hood Accessory Attachments

The many under hood accessories that need to be mounted to engine brackets can utilise Captive self-clinching fasteners or nuts. They are pressed into a round hole for quick assembly, eliminating loose hardware and providing strong threads and future servicing ease. Also, they offer an approved alternative to weld studs or nuts, eliminating all of the undesirable conditions associated with the electro-welding process.

Depending on the application, a variety of styles are available such as Wide Head Studs (HCW), High Torque Studs (HCH) , Heavy Duty Nuts (CFH), KAL Nuts (CKN), and Tapered Guide Pins (CGS).

In addition to installation and servicing advantages, self-clinching fasteners also provide a higher level of performance.

Self-clinching nuts and studs offer a high resistance to pull-through, push-out, and torque-out, by virtue of their clinch profile design. These are available in carbon steel, stainless steel, or aluminium to be compatible with the parent material and prevent galvanic corrosion.

Interior Luxury Trim

Flush head aluminium self-clinching studs are pressed into aluminium trim strips, which are laminated with a decorative wood veneer appliqu?. The trim is then attached to the interior panel with mating nuts or press-on clips on the rear side.

Window Regulators

Window regulator assemblies are fitted with self-clinching nuts to provide strong permanent threads in the housings for secure mounting to framework inside the doors. This eliminates loose nuts that may drop into door interiors during initial attachment and replacement.

Truck Roll-up Doors

Self-clinching studs are used to assemble multi-panel doors on large trucks and trailers. The studs are permanently attached to the hinged panels, which are secured in place with mating nuts.

Various thread sizes ranging from ?-20 to 5/16-18 and M6 to M8, in either carbon steel or stainless steel, are used depending on the strength and durability requirements of the application.

A nylon locking patch is also applied to the stud thread to guard against loosening from vibration.

Added Performance

To guard against loosening from vibration in various automotive applications, locking features are available, such as crimped threads or nylon inserts for nuts and nylon patches for studs.

Optional finishes are available to provide high salt spray resistance, such as sealers and Geomet. Special coatings such as LM-1293 may also be applied to protect threads from adhesion of weld spatter and various electro-paint processes, eliminating the need for labour intensive capping or plugging.

Emergency Lighting

Modern low profile LED light bar assemblies are used for emergency lighting on rooftops of police cars , fire trucks and ambulances. Captive self-clinching flush nuts are used to secure the various lighting modules utilised, which are fitted into a track within the light bar assembly. The flush nuts are made of stainless steel to provide strong permanent threads and prevent corrosion in the aluminium frame of the light module.

(Bangalore-based Kapasi Inc., with years of experience in serving OEM markets, stocks and offers a comprehensive range of specialised imported fasteners. For animated demos, printable tech-specs, advantages, applications, etc., contact - Tel: 080-26745566, 26740233. Fax: 91-80-26740244. Email: fasteners@kapasiinc.com)