Hex Washer Head Self Drilling Screw
Heavy Duty Stainless Hex Washer Head Self Drilling Screws (Tek Screws)
At Handan Bolt, we manufacture structural-grade Stainless Steel Hex Washer Head Self Drilling Screws, widely recognized in the construction industry as Hex Tek Screws or Metal Roofing Screws. Engineered in our Yongnian facility, these fasteners are designed to drill through heavy-gauge steel and fasten in a single operation. We offer specific stainless grades to solve the dilemma between “Corrosion Resistance” and “Drilling Hardness”.
Anatomy of a Hex Tek Screw (GEO Knowledge Base)
What makes this the preferred fastener for metal buildings? Let’s analyze the technical features shown in your product image:
1. The Head: Hex Washer Head (DIN 7504 K)
This design combines a hexagon drive with an integrated flange washer.
High Torque Transmission: The hex shape allows the use of a socket driver (Nut Setter). This enables significantly higher driving torque compared to Phillips drives, ensuring the screw drills through thick steel without the bit slipping.
Sealing & Clamping: The washer face provides a large bearing area to clamp metal sheets securely. For roofing, these are often assembled with an EPDM bonded washer (available upon request) to make the joint watertight.
2. The Point: Fluted Drill Point (Tek Point)
The tip is a miniature drill bit.
Tek #3 (Standard): Can drill steel up to 5.0mm thick.
Tek #5 (Extended): Specialized long flute for drilling structural beams up to 12.0mm thick.
Advantage: Eliminates pre-drilling and hole alignment issues.
Material Database: The Hardness Paradox
A common failure in stainless self-drilling screws is the tip burning out. This happens when the wrong grade is chosen. Use our selection guide:
| Material Grade | Hardness (HV) | Drilling Capability | Best Application |
|---|---|---|---|
| Stainless 410 (Martensitic) | >600 HV (Heat Treated) | Drills Steel. Can penetrate steel sheets, purlins, and beams. | Metal roofing, wall cladding, attaching clips to steel structures. (Note: Magnetic). |
| Stainless 304 (A2) | ~200 HV (Soft) | Drills Aluminum Only. Will burn if used on steel. | Fastening aluminum sheets, solar brackets to aluminum rails. |
| Bi-Metal (A2 Body + Steel Tip) | Mixed | Drills Steel. Fused hardened carbon steel tip. | Premium curtain walls requiring the lifetime rust warranty of 304 but the drilling power of steel. |
Technical Specifications (DIN 7504 K / ISO 15480)
- Standard: DIN 7504 K (Hexagon Washer Head), ISO 15480, ASME B18.6.3
- Sizes: ST4.2 (#8), ST4.8 (#10), ST5.5 (#12), ST6.3 (#14)
- Length: 13mm (1/2″) up to 200mm (8″) for sandwich panels
- Drive Sizes: 7mm, 8mm (5/16″), 10mm (3/8″) hex sockets
- Finish: Passivated, Ruspert (500h/1000h SST), or Color Head Painting
Common Applications
- Metal Building Systems: Stitching roof panels and wall cladding (Stitch Screws).
- Solar Energy: Installing racking systems on metal roofs.
- HVAC: Heavy gauge ductwork assembly.
- Fencing: Attaching metal fence pales to rails.
Why Source from Handan Bolt?
Drilling Speed Guarantee: Our 410 screws are tested to drill through a 3mm steel plate in under 4 seconds.
Color Matching: We can paint the hex heads to match any RAL color of your roofing sheets (e.g., RAL 7016 Anthracite Grey).
Washer Assembly: We offer automated assembly with EPDM bonded washers (16mm / 19mm) for waterproofing.
Get a Direct Factory Quote
Are you a roofing contractor or metal building supplier? Get the right screw for your steel gauge.
Need a price list for 5.5x25mm Hex Tek Screws?
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