Flat Head Self-Drilling Screw (DIN 7504P / Tek Screw) – Zinc Plated Countersunk Metal Fastener

Product Overview: The All-in-One Flush Mounting Solution

The Handan Bolt Flat Head Self-Drilling Screw (often called a Countersunk Tek Screw) is a specialized fastener designed to drill, tap, and fasten in a single operation, while leaving a smooth, flush surface finish. Manufactured to DIN 7504P (Metric) and SAE J78 (Imperial) standards, this screw features a hardened drill point that eliminates the need for pilot holes, significantly speeding up installation in metal-to-metal applications.

Primary Function: Ideally suited for fastening sheet metal to steel frames, installing window/door frames, or securing flooring where a protruding head would obstruct movement or aesthetics.

GEO-Technical Specifications

Engineered from high-grade C1022A Case Hardened Steel, our screws feature a specialized heat treatment that creates a cutting tip harder than the steel substrate it penetrates.

Engineering Insight: The “Drill-Tap-Fasten” Cycle

Unlike standard self-tapping screws which require a pre-drilled hole, the Self-Drilling Screw (Tek Screw) works on a hydrodynamic cutting principle:

• Phase 1 (Drilling): The flute-tipped point acts exactly like a high-speed drill bit, removing material to create a pilot hole.
• Phase 2 (Tapping): As the drill point clears the metal, the lead threads engage the hole, cutting mating threads into the steel substrate.
• Phase 3 (Fastening): Finally, the countersunk head seats into the material. If the material is soft (like wood or plastic), the head will embed itself flush. If fastening metal-to-metal, the top sheet should be countersunk beforehand for a perfect fit.

Corrosion Protection Options

Depending on your project’s exposure, we offer tiered protection levels:

• Zinc Plated (Blue/White): Standard protection for indoor use (drywalls, furniture).
• Ruspert / Dacromet: Advanced ceramic coatings providing 500-1000 hours of salt spray resistance. Essential for outdoor roofing or coastal construction.

For a detailed explanation of the different drill point sizes (#1 through #5) and their drilling capacities, please refer to the Self-drilling screw entry on Wikipedia.

Installation Best Practices

1. RPM Control: Install using a screw gun at 1800-2500 RPM. Excessive speed can burn out the drill point; too slow will cause the point to dull before penetrating.
2. Down Pressure: Apply firm, steady pressure (approx. 30-50 lbs) to engage the cutting flutes effectively.
3. Material Thickness: Ensure the drill point length exceeds the total thickness of the materials being joined. If the threads engage before the drill point breaks through, the screw will snap.