What Is A Captive Screw?

05/08/2016

Captive Screws are one of AccuGroup’s most popular specialist products. ‘Captive Screws’ are actually very a broad category of fasteners which are defined by their inability to be fully removed from a hole after installation.

Many companies offer captive fastener variants which incorporate large grommets, overlapping screw heads, or spring-loaded mechanisms, but the most efficient and compact solution is through the use of an unthreaded shank and a Captive Washer.

During installation, the head of a Captive Screw and a Captive Washer are placed on either side of a loose panel or target housing. During installation, the screw is tightened, and the curved flaps of the washer are flattened, reducing the internal diameter of the Washer and preventing it from passing back over the threads of the Screw. AccuGroup’s Captive Washers are specially designed with this installation method in mind.

Military and Precision Engineering Applications

This type of fastener sees a large amount of use in industrial machinery, where lost or loose screws can cause catastrophic damage to a production line, particularly if a loose screw falls into a mechanism. Captive Screws are also required in certain military applications, where panels must be removed and reinstalled quickly and efficiently.

Captive fasteners are required by law on many pieces of machinery and safety equipment, and must applied to equipment such as safety guards for compliance with EU Machine Safety Directive 2006/42/EC.

Specialist Manufacture Process

Captive Screws are a variant of AccuGroup’s wide range of standard high-precision Screws. This means that we are able to offer one of the largest standard Captive Screw ranges in Europe. By using our standard components as a starting point in this process, we can ensure the absolute quality and precision which is fundamental to the AccuGroup brand.

An AccuGroup Captive Screw is manufactured to the highest standards. The unthreaded section is a Captive Screw's most important feature, and must operate efficiently to ensure ease of use. Many of these fasteners, such as Captive Thumb Screws are also operated by hand, and must be free from sharp edges. For these reasons, we ensure that all Captive Screws we manufacture are well-finished, and are provided with a smooth and precise unthreaded shank. All components within this range are manufactured to a precise general tolerance of +/- 0.13mm, with even tighter tolerances available on request.

Material Choices

Captive Screws can be custom manufactured from a selection of specialist materials. Lightweight Aluminium, wear-absorbent Brass, and ultra-lightweight PEEK Thermoplastic are just some of the materials we can offer.

Sppecialist finishes such as PX-3 Chemical Blackening and Resin Locking Patches are also available.

Custom Sizes

Captive Screws are available in standard metric and imperial ranges. As standard, metric diameters range from M1.4 up to M12, and lengths range from 6mm up to 300mm. Imperial thread sizes include both UNF and UNC threads, and range in diameter from No.0 all the way up to 1 inch.

Captive Screws are often manufactured to order, meaning that there is often a high degree of customisability in the design process, this means that non-standard dimensions and modifications can usually be made on request. Contact us for any queries, or to receive a quotation on Captive Screw manufacture.

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