Self-drilling/self-tapping screws for metals and plastics – ex-stock from Challenge Europe are often used in the construction industry, e.g. for fixing sheet metal in place on frameworks and can come with bonded washers to prevent water ingress in outdoor applications. Self-drilling screws come in a variety of formats but all are based upon the principle of drilling and tapping in one operation. They are generally used in steel, softer metals or plastics and there is a range specially designed for use in wood/composite materials.

Major benefits in using this type of fastening include increased speed of installation and efficiency provided by combining the drilling and tapping operations as well as a functional improvement in alignment, which otherwise could require re-setting the screw for correct fitment.

Self-tapping screws are stocked in depth as hardened and plated carbon steel and stainless steel self-tappers for use mainly in sheet steel products. These screws form or tap their own thread so saving time and providing a strong clamping action with the ability to remove and replace if required. Countersunk, Pan, and Flange heads are commonly available, the flange head having the advantage of spreading the load well and minimising deformation of the sheet thus eliminating the need for an under head washer. The traditional slotted drive is still available, but the modern preference is for cross recessed or multi-splined (star) drives to suit modern insertion equipment. Self-drilling and self-tapping screws are available in plated steel and stainless steel for engineering, construction and general assembly purposes.

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Specialist Construction screws are often thought of as a separate genre but principally operate in the same way as their more standard cousins and tend to be designed to perform more specific functions. These functions range from having integrated sealing washers, for the fixing of cladding, through to Bugle head designs for use in fixing plasterboard. There are a variety of drives available, often linked to the intended function of the fixing, and can include designs such as Hex, Star, Pozi, Phillips and even Square. Some fixings are available in a Collated format where speed and handling is important.

Largely because of their wide utility this group of self-drilling/self-tapping screws offer an extensive range of different head and drive types. Head types include the following and may often be specified with a drive configuration of choice:

• Pan head: which has a thick rounded, outer top with a large surface area

• Button or dome head: which is cylindrical head with a dome shaped top

• Countersunk or flat head: An inverted cone head with a flat outer surface

• Raised countersunk head: Combines a countersunk head with a rounded upper surface for decorative purposes

• Bugle head: which presents a smooth increasing transition from the shank to the angle of the head

• Flanged head: Can be any head style incorporating an integrated flange so that it does not require a washer

Also wafer head – which is very thin – for use where a low profile is required.

In some instances they can also be offered with anti-vandal features, such as pin hexagon, pin star (multi-splined) and clutch head.

Further information on Challenge Europe products can be found at www.challenge-europe.co.uk.