Characteristics of uPVC Tapping (PVC) Screws:

• Self-Tapping: They create their own thread as they are driven into the uPVC material. This is crucial as uPVC is not like wood (where a standard screw “bites”) or metal (where a machine screw needs a pre-tapped thread).

• Thread Profile: Often feature a specific thread angle and pitch that is optimized for plastic, preventing cracking and providing good pull-out resistance. “Hi-low” threads are common, which have alternating high and low threads to provide strong engagement without excessive stress.

• Sharp Point: Many have a very sharp, gimlet point to allow them to enter the uPVC easily, sometimes without a pilot hole, though for a cleaner finish and to prevent splitting, a small pilot hole is often recommended.

• Head Types: Usually countersunk (for a flush finish) or pan head/wafer head (for a broader clamping surface).

• Corrosion Resistance: Like all uPVC screws, they must be corrosion-resistant (e.g., zinc plated, galvanized, or stainless steel) to prevent rust stains on the white uPVC.

• Sizes: Commonly available in smaller diameters (e.g., 3.9mm, 4.2mm) and various lengths depending on the thickness of the uPVC profile and the component being fixed.