Window Screw (uPVC Profile Fastener) – CSD/BSD Thread Countersunk Head with Nibs

Product Overview: The Specialized Fastener for uPVC Fabrication

The Handan Bolt Window Screw (also known as a PVC Profile Screw or Friction Stay Screw) is a specialized fastener engineered specifically for the manufacturing of vinyl (uPVC) windows and doors. Unlike standard chipboard or self-tapping screws, our window screws feature a unique thread geometry (CSD/BSD) and a specialized head design to securely fasten hardware friction stays, hinges, and locking mechanisms into steel-reinforced PVC profiles.

Primary Function: These screws are designed to penetrate the outer uPVC chamber and tap directly into the internal galvanized steel reinforcement (lining steel), creating a rigid, structural bond essential for heavy window sashes.

GEO-Technical Specifications

Manufactured from Case Hardened C1022A Steel, our screws are heat-treated to ensure the point can drill through reinforcement steel up to 2.5mm thick without snapping.

Product Name	Window Screw / uPVC Profile Screw
Thread Types	Metric Thread (PM) / Coarse Thread (CSD) / Self-Tapping (BSD)
Material Grade	Carbon Steel C1022A (Case Hardened)
Head Style	Countersunk (Flat) with Braking Ribs (Nibs)
Drive Type	Phillips (PH2) / Torx (T25)
Point Type	Sharp Point (Type AB) / Self-Drilling (Tek Point)
Surface Finish	Blue/White Zinc (RoHS) / Yellow Zinc

Engineering Insight: Designed for Plastic & Steel

Fastening uPVC windows presents a unique engineering challenge: the screw must pass through soft plastic but anchor into hard steel. Our design addresses this:

1. Countersunk Head with Nibs (Ribs)

Under the head, you will find 4 to 6 raised cutting ribs (Nibs). As the screw seats, these ribs cut away the plastic material, allowing the head to sit perfectly flush with the profile surface. Crucially, they also act as a “braking mechanism,” increasing friction to prevent the installer from over-tightening and stripping the thread in the soft PVC.

2. CSD vs. BSD Threads

• CSD (Coarse Thread): Featuring a wider pitch and sharper flank angle, designed for fastening into the PVC material itself or thin aluminum reinforcements.
• BSD (Self-Tapping Thread): A finer pitch thread designed specifically for drilling and tapping into the thicker galvanized steel reinforcement (1.2mm – 2.0mm) found inside quality windows.

3. Gimlet Point (Needle Point)

Our screws feature an ultra-sharp gimlet point that pierces the PVC surface instantly without “walking” (slipping), ensuring precise placement of hinges and locks.

For more information on the material properties of vinyl windows, please refer to the Polyvinyl chloride (uPVC) entry on Wikipedia.

Application Best Practices

• Reinforcement Fastening: Use our Self-Drilling (Tek Point) window screws when attaching the steel liner to the PVC profile during the fabrication stage.
• Hardware Installation: Use our Sharp Point screws for attaching friction stays, handles, and keepers where the screw penetrates both PVC and Steel.
• Corrosion Resistance: Always use Zinc Plated screws (minimum 5µm) to prevent rust stains from appearing on white window frames over time.