Self-clinching Fasteners Flush-head vs Concealed head
Self-clinching fasteners are threaded nuts, studs, or standoffs that are mechanically pressed into metal, therefore becoming a permanent part of the panel, enclosure, or bracket. Each self-clinching fastener is used for something different. Nuts accept bolts and screws to hold components securely in place. Stand-offs are mainly used to mount circuit boards, so they are not shorted by contacting sheet metal that has an electrical current flowing through. They also help prevent overheating. Studs are used to mount connectors or other components by providing a threaded screw within the enclosure. Self-clinching fasteners can be one of two types: flush-head or concealed-head. This blog will cover both types and how they are used.
Flush-head Fasteners
Flush-head fasteners are mechanically pressed through a hole in the sheet metal from the outside, allowing them to sit mostly flush with the outside edge. There is a slight indentation around the exterior of the metal where it gets pressed, meaning they are not completely flush and making them detectable. This minor indentation can be diminished by grinding down the metal so the fastener sits more flush with the host material, and can be made even more undetectable if a textured powder coat is applied to the sheet. Both these methods will make flush-head fasteners less noticeable to the eye, though they will still be felt by touch.
Concealed-head Fasteners
While flush-head fasteners are installed by being pushed through the metal, concealed-head fasteners are inserted into a machined blind pocket so that there is no contact with the outer edge. These pockets are created either by a CNC mill or router. Concealed-head fasteners are frequently used for cosmetic reasons. Despite this, they are also ideal for meeting requirements related to air/watertightness, because the hole to insert the fastener only goes partially through the metal. Concealed-head fasteners are also ideal for meeting ingress protection needs. If you choose concealed-head fasteners for your application, be aware that they require a minimum sheet thickness. This is to ensure that the CNC mill or router will have sufficient room to machine a deep enough hole for the pocket where the fastener will sit.Though both of these fastener types achieve a very similar function, there are multiple critical differences between them. These include installation method, profile, air/watertightness, price, and height.
Installation Method
Flush head fasteners are pressed through the exterior of the metal while concealed-head fasteners are pressed into a fitted pocket from the side on which they are used.
Profile
Fasteners have different profiles depending on their installation methods. Flush-head fasteners are slightly noticeable from the outside, although this can be minimized through the use of grinding and powder coat. Concealed-head fasteners have no noticeable profile. As such, they are most commonly used when cosmetics are a priority.
Air/watertightness
Because flush-head fasteners go through the metal, they are not air/watertight. Concealed-head fasteners are a better option if tightness to water, air, or radio waves is necessary.
Price
Flush-head fasteners are typically slightly cheaper than concealed-head fasteners, partially because concealed-head fasteners take more time and effort to install. Both cost slightly more than conventional fasteners, though fasteners are not considered a particularly expensive element of a custom enclosure or part.
Height
There is a difference in height after these two types of fasteners are installed. Concealed-head fasteners are measured from the interior of the surface from where the fastener is installed, while flush-head fasteners are measured from the outside of the enclosure’s surface where they are directed through the metal.
Whether you need flush-head or concealed-head fasteners, Aviation Axis can help. Owned and operated by ASAP Semiconductor, we can help you find all types of fasteners and many other parts for the aerospace, civil aviation, defense, industrial, and electronics markets. This includes fastener blind flush heads and bolt flush heads with part numbers 99-1495036, MS90353-0502, MS90353U0808W from Bombardier Aerospace. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, call us at 1-714-705-4780 or email us at sales@aviationaxis.com.
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