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Countersunk Screws.

Countersunk Screws

What are Countersunk Screws?

Countersunk screws, a key component in the precision screw family, are characterised by their unique design which allows them to sit flush with or below the surface of the material they are inserted into.

These screws feature a conical head with a flat top and a tapered underside. The design is not just about aesthetics; it serves a practical purpose too. When driven into a material, the tapered head of a countersunk bolt aligns with the angled countersink hole, resulting in an installation that is perfectly flush with or below the surface. They can also be used alongside countersunk washers for aesthetic purposes or when you need to use countersunk bolts and nuts together.

How Countersunk Bolts Work.

Countersunk bolts, specialising in providing a smooth, level finish in wood, metal, and plastic surfaces, are installed into pre-tapped holes that have also been countersunk. Championed in industries from automotive projects to complex aerospace engineering, countersunk head screws are indispensable thanks to their head profile.

For instance, in the aviation industry, countersunk bolts work to ensure minimal air resistance on the fuselage of a plane. Their ability to lie flush with the surface also makes them ideal for safety in play equipment or in tight-tolerance moving machinery, where protruding screw heads can be a hazard.

Materials and Benefits.

At Accu, our countersunk screws come in various materials like 10.9 and 12.9 high-tensile steel, A2 and A4 stainless steel, and Bumax. Each material offers unique benefits. For instance, A4 stainless steel countersunk screws offer corrosion resistance and strength, making them ideal for outdoor or marine environments. The high-tensile steel variants provide superior strength for heavy-duty applications. The choice of material significantly impacts the screw's performance in different settings so make sure to mate this choice with your project needs.

Sizes, Types, and Finishes.

Our range of countersunk screw dimensions spans from the petite M2 (2mm) thread size to the robust M24 (24mm), with thread lengths varying from 3mm to a substantial 200mm. This extensive variety caters to virtually any requirement and includes our best-selling M6, M8 and M10 countersunk bolts.

Special finishes like hot dip galvanising and zinc plating enhance the screw's durability against corrosive environments whereas AccuBlack chemical blackening produces amazing-looking black countersunk screws for a blacked-out aesthetic. To thwart loosening against vibrations, our range also offers pre-thread lock applied countersunk components that can save time and money when it comes to assembly.

Finally, adding to the versatility of these components, our range includes all your favourite drive types from countersunk socket screws to Phillips, Pozi, slotted and Torx drive options.


Q: What is the difference between a screw and a countersunk screw?.

A: The core difference is that the head profile on a countersunk bolt is tapered and designed to sit flush with their target in a countersink, whereas standard screws may protrude and have a differently shaped head like the cylindrical one on cap head screws.

Q: What are countersunk screws used for?.

A: Countersunk screws are designed for applications where a smooth, flat surface is required, like car or aircraft manufacturing where every incremental gain in aerodynamics can prove instrumental.

Q: What is another name for a countersunk screw?.

A: They are sometimes referred to as "flat-head screws" in carpentry however that naming convention often implies the inclusion of self-tapping threads similar to wood screws rather than the machined threads of a countersunk machine screw.

Q: What is the difference between countersink and countersunk?.

A: "Countersink" is the process of creating a conical hole for the screw to sit within, while "countersunk" describes the profile of the screw head itself.

Q: Can I use a washer with a countersunk screw?.

A: Yes, but you must ensure to use countersunk washers to maintain a flat surface and evenly distribute the load.

Q: What are non-countersunk screws called?.

A: When it comes to screws, countersunk is simply one head profile, other types of non-countersunk screws go by cap head, pan head, cheese head, button head and grub screws.

Bespoke Countersunk Screws Manufacture.

High precision, bespoke manufacture of Countersunk Screws to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.

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