Evolution Stainless Steel Tec Screw 5.5mm x 50mm c/w washer (BMBW5.5-50-3) - Box of 100 by Evolution Fasteners

The Evolution 5.5mm x 50mm Stainless Steel Tec Screw is a high-quality self-drilling fastener designed for light steel sections and external applications. It combines a stainless steel shank and head with a hardened carbon steel drill tip, offering excellent corrosion resistance and reliable drilling performance. This Tec screw features a hexagonal head and comes complete with a 16mm bonded washer, ensuring a secure fix and a weather-tight seal. It is ideal for situations where a durable stainless steel fixing is required, allowing you to fasten metal panels and sheets without pre-drilling.

Key Features

• Bi-Metal Construction – Stainless steel body (A2 grade 304) provides corrosion resistance, while a hardened carbon steel Tek 3 drill point easily cuts through steel. This design ensures durability and prevents rust, making it suitable for outdoor use.
• Self-Drilling Tip – Equipped with a Tek 3 self-drilling tip, it can drill through steel sections up to ~4.0 mm thick without the need for pre-drilling. This speeds up installation and guarantees a firm hold in light gauge metals.
• Hex Washer Head – Hexagon 5/16″ head allows high torque transfer and easy driving with a standard hex bit. The integrated flange under the head provides extra support, and the screw is supplied with a 16 mm EPDM bonded washer for a secure, leak-proof seal.
• Weatherproof Seal – The included EPDM rubber washer is bonded to a stainless steel backing, ensuring a weather-resistant seal around the fastening point. This prevents water ingress, making the screw perfect for roofing and cladding use.
• High Strength & Reliability – Designed and tested for construction applications, this screw delivers strong tensile and shear performance. The coarse thread (for Tek 3) guarantees excellent pull-out resistance in thin steel, ensuring fixtures remain firmly in place over time.

Applications

• Roofing Sheets to Purlins – Ideal for fixing metal roofing sheets to light-gauge steel purlins and frames, providing a secure attachment that resists corrosion in exposed environments.
• Wall Cladding Panels – Used for fastening steel or aluminium cladding panels to structural steel members (hot or cold rolled rails), ensuring facades are attached strongly and sealed against weather.
• Aluminium Fabrications – Suitable for attaching aluminium sheets, panels, or flashings to steel supports when a stainless steel fastener is required to avoid bimetallic corrosion and maintain appearance.
• External Metalwork – Perfect for outdoor steel constructions like sheds, garages, and architectural features, where its stainless steel composition offers longevity.
• General Construction – Useful for any application requiring a rust-resistant, self-drilling screw in thin steel sections – from HVAC installations to fencing and enclosures.

Specifications

• Diameter x Length: 5.5 mm x 50 mm
• Head Type: 5/16″ AF hexagon head with integrated washer flange
• Drive Type: Hex socket (use 5/16″ hex driver bit)
• Material: A2 Stainless Steel (304) screw body and head; hardened carbon steel drilling tip (zinc electroplated for corrosion protection)
• Drill Tip: Tek 3 self-drilling point (drilling capacity approx. 1.2 mm – 4.0 mm steel thickness)
• Thread Type: Coarse self-tapping thread (suitable for light gauge steel)
• Washer: 16 mm diameter bonded washer (stainless steel backing with EPDM rubber seal) – included with screw
• Standards: Complies with BS EN ISO 3506-1 (mechanical properties of stainless steel fasteners)
• Typical Use: Light section steel connections, external cladding/roofing projects