M3.5 x 50mm Flat-Head Countersunk Electrical Screw - Black, 100 Pack

These M3.5 x 50mm flat-head countersunk electrical screws are designed for installing screwless faceplates and flat-plate electrical accessories where the screw head needs to sit flush with or below the surface. The 50mm length provides sufficient thread engagement for typical back box to sub-frame installation depths, while the 3.5mm diameter matches the standard pilot hole size in metal electrical back boxes and sub-frames.

Supplied in packs of 100, these screws are suited to trade installations and larger residential projects where multiple socket or switch faceplates are being fitted. The flat countersunk head allows the screw to sit within the aperture of the sub-frame without protruding, which is required for screwless cover plates to clip cleanly onto the frame. The black finish blends with the interior of most back boxes and sub-frames, reducing visual prominence if the screw head is visible through any gaps.

The screws are designed for machine threading into metal sub-frames rather than wood or plasterboard. The 50mm length is longer than typical electrical fixing screws (which are often 25-35mm), making them suitable for installations where the back box is recessed deeper into the wall or where the sub-frame sits proud of the back box surface. The black coating is a surface finish rather than corrosion-resistant plating, so these screws are intended for dry indoor electrical installations only.

Product Specification Sheet

What are these screws used for?

These screws fix the metal sub-frame of screwless electrical faceplates to the back box. The flat countersunk head sits flush or below the sub-frame surface, allowing the screwless cover plate to clip onto the frame without interference from protruding screw heads.

Why 50mm length instead of the standard 25-35mm screws?

The 50mm length accommodates deeper back box installations or situations where the sub-frame sits proud of the back box surface. If the back box is recessed into the wall or if there's a plasterboard spacer behind the sub-frame, the additional length ensures sufficient thread engagement.

Can these be used outdoors or in bathrooms?

The black finish is a surface coating rather than corrosion-resistant plating, so these screws are intended for dry indoor electrical installations only. For outdoor or high-moisture environments, stainless steel or zinc-plated screws are recommended.

How many screws are needed per faceplate?

Most single-gang sub-frames use two screws (top and bottom). Double-gang and larger sub-frames typically use four screws. A 100-pack covers approximately 25-50 faceplates depending on the gang size.