Stainless Steel Hex Washer Head Self-Drilling Screw (DIN 7504K) – With EPDM Bonded Washer for Roofing & Solar

Product Overview: The Ultimate Weather-Proof Fastening Solution

The Handan Bolt Stainless Steel Hex Washer Head Self-Drilling Screw is a premium-grade fastener designed for applications where failure is not an option. Combining the high torque transmission of a hex drive, the drilling efficiency of a Tek point, and the superior corrosion resistance of stainless steel, this screw is the industry standard for Solar Panel Mounting, Metal Roofing, and Marine Construction. It comes pre-assembled with a high-quality EPDM bonded washer to guarantee a watertight seal.

Primary Function: Engineered to drill through aluminum or steel sheets and fasten them securely while withstanding decades of exposure to rain, UV radiation, and salt spray without rusting.

GEO-Technical Specifications

Unlike standard carbon steel screws, our stainless series uses specialized metallurgy to balance hardness (for drilling) and corrosion resistance.

Engineering Insight: The Role of EPDM Washers

The included washer is not just a piece of rubber; it is a critical engineering component:

• Waterproofing: EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber that resists UV degradation and temperature extremes. When compressed, it flows into the threads and screw hole, blocking water ingress.
• Vibration Damping: The rubber layer absorbs structural vibration caused by wind loads, preventing the screw from backing out.
• Dielectric Insulation: In dissimilar metal applications (e.g., stainless screw on aluminum sheet), the washer acts as an insulator to minimize galvanic corrosion.

Material Selection: SS410 vs. Bi-Metal

Choosing the right stainless grade is crucial:

• Stainless Steel 410: This is a magnetic, heat-treatable stainless steel. It is hard enough to drill through steel sheets but offers moderate corrosion resistance. Ideal for inland roofing.
• Bi-Metal (A2/A4): For coastal areas, we fuse a Carbon Steel drill point to a Stainless Steel 304/316 shank. This gives you the drilling power of carbon steel with the ultimate rust protection of marine-grade stainless.

For more details on the properties of different stainless steel grades, please refer to the Stainless steel grades entry on Wikipedia.

Application Best Practices

• Torque Control: Use a depth-sensing screw gun. Over-torquing can crush the EPDM washer, causing it to split and leak. The washer should be compressed so the rubber is visible around the edges, but not bulging excessively.
• RPM Speed: Stainless steel work hardens quickly. Drive at a steady, lower RPM (1500-1800) compared to carbon steel screws to prevent the point from burning out.