What types of rivets and push-in fasteners are available?
Although many different versions are available, we basically distinguish only three.
Expansion rivets
Plastic expansion rivets are usually two-piece. The fastening method is based on a spreader shank that expands under the influence of a pin or screw being driven in. Fastening is done in two steps, first the rivet is inserted into the hole, then the driving pin or screw is pushed in and thus the fastening is achieved. Expansion rivets have a high pull-out resistance due to the mechanical locking by pin or screw.
Basicly plastic expansion rivets follow the same basic principle as with metal rivets or pop rivets; a body expands in response to a driving pin. Unlike ordinary rivets, plastic rivets are generally detachable and therefore reusable. Well-known examples are plastic screw rivets and split rivets.
Plastic expansion rivets are generally used to join parts or panels and where higher resistance to shear forces and pull-out is required.
Push rivets
Plastic push-in rivets are usually one-piece. The fastening method is often based on barbs, ribs or specific shape. Easy to fix, simply press into the bore. Push rivets generally have a lower pull-out resistance than spread rivets, in addition a lower shear value. These are lower because the core of the fastener is simply less solid than with expansion rivets.
Push-in rivets with barbs or ribs are generally not reusable, as the ribs are often damaged after being pulled out. Push-in rivets with a specific shape are sometimes removable. Well-known examples are the so-called pine tree or fir tree rivets or barbed rivets, arrow clips etc.
Two-piece snap rivets
Two-piece snap rivets, or ratchet rivets, consist of two separate parts that are pressed together and therefore interlock. Usually, both parts have a head, providing a neat finish on both sides. The elongation resistance and shear value are usually high. As a rule, this type of pressure rivets is not detachable or reusable. Two-piece plastic snap rivets are a good alternative to bushing screws or double cap rivets.
What are the advantages of push-in and snap fasteners?
The major advantage of push-in and snap fasteners are that they can provide a simple, inexpensive, strong, fast and neat finished connection between e.g. sheet material, cladding or other components. Whereas traditional fasteners such as screws etc. take time to tighten, pressure fasteners are simply pressed into a bore or snaped together and thus the fastening is generally achieved. Not surprisingly, push-in and snap fasteners are also referred to as quick fasteners and therefore frequently applied in the automotive industry and electrical engineering.
The plastics used in push-in, snap and compression rivets have good chemical and corrosion resistance, are electrically insulating and lightweight. Moreover, plastic is able to reduce vibrations and resonance. A number of versions even have a fire behaviour UL classification, which can be important in electrical installations and automotive.
Expansion rivets are often used to fix bumpers, sheet metal and cladding, for example. Push-in fasteners are also used to secure electrical components on, for example, switch panels, e.g. fans, etc. Due to their versatility, the number of application examples is vast.
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