Product Overview 410 / 304 stainless steel hex washer head self-drilling screws (also known as stainless steel Tek screws or self-drilling roofing screws) are corrosion-resistant fasteners designed for fastening metal roofing sheets, steel cladding, and light-gauge steel structures to steel or timber substrates. The hexagonal washer head provides a large bearing surface and is driven with a standard hex socket, while the integrated EPDM-bonded sealing washer creates a watertight seal around the drilled hole. These screws are available in two stainless steel grades to suit different application requirements: 410 stainless steel (martensitic) — Heat-treatable, achieving high surface hardness (HRC 53–58 at the drill tip) for excellent drilling performance through steel plates. Offers moderate corrosion resistance, better than carbon steel but lower than 304. Ideal for general steel-to-steel fastening in inland, low-humidity environments. 304 stainless steel (austenitic) — Non-heat-treatable but with superior corrosion resistance (≥720 hours salt-spray), making it ideal for coastal, humid, and chemically exposed environments. Lower hardness means it is best suited for fastening to aluminum, plastic, or wood substrates rather than thick steel plates. These screws are manufactured to DIN 7504 K (hexagon washer head self-drilling screw) and ISO 15480 standards. DIN 7504 K specifies the dimensions, material, mechanical properties, and performance requirements for hexagon washer head self-drilling screws with a drilling capacity for steel sheets; it has been replaced by ISO 15480, and the two standards are interchangeable.Available in diameters ST4.2, ST4.8, ST5.5, and ST6.3 mm, with lengths ranging from 13 mm to 150 mm. Material Comparison: 410 vs 304 Stainless Steel Property 410 Stainless Steel 304 Stainless Steel Crystal Structure Martensitic Austenitic Magnetic Yes No (slightly magnetic after cold working) Heat Treatable Yes (can be hardened) No Surface Hardness HRC 53–58 (drill tip) HRC ≤ 20 Core Hardness HRC 35–45 HRC ≤ 20 Tensile Strength 600–800 MPa 500–600 MPa Corrosion Resistance Moderate (better than carbon steel) Excellent Salt Spray (ASTM B117) ~500 hours ≥720 hours Drilling Capacity Steel plates up to 12.5 mm Aluminum, plastic, wood only Best Application Steel-to-steel fastening, general construction Coastal, humid, chemical environments Key selection guidance: 410 stainless steel balances drilling performance and rust protection — it offers high hardness with excellent drilling performance, close to carbon steel, but has lower corrosion resistance than 304. 304 stainless steel highlights superior corrosion resistance and is ideal for environments exposed to moisture or chemicals. The 410 material is the mainstream choice for self-drilling screws requiring penetration through steel plates; 304 is preferred for outdoor metal roofing, equipment enclosures, and long-term service in corrosive environments. Standard & Compliance Parameter Specification Standard DIN 7504 K (hexagon washer head self-drilling screw); ISO 15480 Material 410 (1Cr13) martensitic stainless steel / 304 (0Cr18Ni9) austenitic stainless steel Thread Type Self-drilling thread (ST), Type 17 point Head Type Hexagonal washer head with integrated EPDM sealing washer Finish Passivated (natural stainless) Corrosion Resistance 410: ~500 hrs salt spray; 304: ≥720 hrs salt spray (ASTM B117) Sealing Washer EPDM bonded washer (UV-resistant, −40 °C to +120 °C) Drilling Capacity Up to 12.5 mm steel plate (depending on screw diameter and material) Diameter Range ST3.5 / ST3.9 / ST4.2 / ST4.8 / ST5.5 / ST6.3 mm Length Range 9.5 mm – 160 mm Size Range & Specifications Screw Size Diameter (mm) Standard Lengths (mm) Hex Drive Typical Application ST3.5 3.5 9.5 / 13 / 16 / 19 / 22 / 25 6 mm Light sheet metal, thin panels ST3.9 3.9 13 / 16 / 19 / 22 / 25 7 mm Light roofing, ductwork ST4.2 4.2 13 / 16 / 19 / 22 / 25 / 32 7 mm Light roofing, cladding ST4.8 4.8 13 / 16 / 19 / 22 / 25 / 32 / 38 / 45 / 50 8 mm Standard roofing, HVAC ST5.5 5.5 19 / 25 / 32 / 38 / 45 / 50 / 60 / 70 / 75 8 mm Heavy roofing, steel cladding ST6.3 6.3 19 / 25 / 32 / 38 / 45 / 50 / 60 / 70 / 75 / 80 / 90 / 100 / 110 / 120 / 125 / 130 / 140 / 150 / 160 8 mm / 10 mm Heavy-duty roofing, structural connections Custom lengths and diameters available upon request. Product Features Two Stainless Steel Grades Available — Choose 410 for high-hardness drilling through steel plates, or 304 for superior corrosion resistance in harsh environments. Both grades are available in the same size range and head configuration. Self-Drilling Point (Tek Point) — The hardened drill point penetrates steel sheets without pre-drilling, reducing installation time and labor costs. 410 stainless steel achieves the required hardness through heat treatment; 304 stainless steel offers drilling capability for softer substrates. Hex Washer Head — Large bearing surface distributes clamping force evenly and prevents damage to roofing sheets. Compatible with standard hex socket drivers. EPDM-Bonded Sealing Washer — The UV-resistant EPDM washer compresses against the roofing sheet to create a watertight seal, preventing water ingress at the fastener penetration point. Superior Holding Force — High toughness and holding force prevent loosening over time, even under vibration and thermal cycling. Wide Range of Sizes — Diameters from ST3.5 to ST6.3 mm, lengths from 9.5 mm to 160 mm, covering virtually all roofing, cladding, and general fastening requirements. Eco-Friendly Finish — Natural stainless finish eliminates the need for zinc plating or coatings, avoiding hexavalent chromium concerns and supporting sustainability goals in Middle East construction projects. Applications 410 / 304 stainless steel hex washer head self-drilling screws are widely used in: Metal Roofing Installation — Fastening corrugated and trapezoidal steel roofing sheets to purlins, rafters, and steel frames. 410 is suitable for general construction; 304 is recommended for coastal and high-humidity areas. Wall Cladding — Attaching metal wall panels, sandwich panels, and composite cladding to steel or timber structures. Marine & Offshore — Deck fastening, dock structures, and offshore platform applications where saltwater corrosion is a concern (304 recommended). Solar Panel Mounting — Fastening mounting rails and brackets to roof structures in solar energy installations. HVAC Ductwork — Securing duct insulation, hangers, and flashing in commercial and industrial buildings. Steel Framing — Light-gauge steel framing connections for partitions and ceilings. Agricultural Buildings — Poultry houses, barns, and storage facilities (304 recommended for ammonia exposure). Installation Guidelines Select the correct screw material — Use 410 stainless steel for fastening to steel plates; use 304 stainless steel for fastening to aluminum, plastic, or wood substrates, or for highly corrosive environments. Select the correct screw length — The screw should penetrate the substrate by at least 25 mm beyond the total thickness of the material being fastened. Use a variable-speed screwdriver — Drive at low speed (1,500–2,500 RPM) with steady pressure until the EPDM washer compresses slightly against the roofing sheet. Do not over-tighten — Excessive torque will compress the EPDM washer beyond its elastic limit and cause water leakage or damage to the roofing sheet. Drive perpendicular to the surface — Angled installation prevents the washer from seating properly and creates an incomplete seal. Inspect after installation — Check that all washers are properly compressed and no screws are over-driven or protruding. Quality Assurance All screws are manufactured under strict quality control and can be supplied with: Mill Certificates — material test reports with chemical composition and mechanical properties (410 / 304 verification) Hardness test reports — surface and core hardness verification (for 410) Salt spray test reports — corrosion resistance verification (ASTM B117) Drilling capacity test reports — verification of drilling performance Torque test reports — verification of torsional strength Third-party inspection reports (SGS, BV, TÜV) — available upon request EN 10204 3.1 Inspection Certificates — available upon request Ordering Information To place an order or request a quotation, please provide: Material grade (410 / 304) Screw size (ST3.5, ST3.9, ST4.2, ST4.8, ST5.5, ST6.3 mm) Length(s) required Quantity per size Certification requirements Packaging preferences