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China Suppliers Factory Galvanized Countersunk Cross Tapping Screws - Self Tapping Screws for Secure Installation
Thread Specifications
| Thread specifications | ST2.2 | ST2.9 | ST3.5 | ST4.2 | ST4.8 | ST5.5 | ST6.3 | ST8 | ST9.5 | |||
| P | Pitch | 0.8 | 1.1 | 1.3 | 1.4 | 1.6 | 1.8 | 1.8 | 2.1 | 2.1 | ||
| a | Max | 1.6 | 2.2 | 2.6 | 2.8 | 3.2 | 3.6 | 3.6 | 4.2 | 4.2 | ||
| dk | Max | 3.8 | 5.5 | 7.3 | 8.4 | 9.3 | 10.3 | 11.3 | 15.8 | 18.3 | ||
| Min | 3.5 | 5.2 | 6.9 | 8 | 8.9 | 9.9 | 10.9 | 15.4 | 17.8 | |||
| k | Max | 1.1 | 1.7 | 2.35 | 2.6 | 2.8 | 3 | 3.15 | 4.65 | 5.25 | ||
| Slot Number | 0 | 1 | 2 | 2 | 2 | 3 | 3 | 4 | 4 | |||
| M1 | Cruciform | 1.9 | 3.2 | 4.4 | 4.6 | 5.2 | 6.6 | 6.8 | 8.9 | 10 | ||
| M2 | Zigzag slot | 2 | 3 | 4.1 | 4.4 | 4.9 | 6.3 | 6.6 | 8.8 | 9.8 | ||
| y | Reference value | Type C | 2 | 2.6 | 3.2 | 3.7 | 4.3 | 5 | 6 | 7.5 | 8 | |
| Type F | 1.6 | 2.1 | 2.5 | 2.8 | 3.2 | 3.6 | 3.6 | 4.2 | 4.2 | |||
| Type R | / | / | 2.7 | 3.2 | 3.6 | 4.3 | 5 | |||||
How to Choose a Suitable Self Tapping Screw
- 1 Select by material: Select different self tapping screws based on the material characteristics that need to be nailed in. For example, for hard materials, choose self tapping screws with high strength, appropriate length and diameter.
- 2 According to thread selection: Self tapping screws usually have two types: coarse thread and fine thread, and different threads are usually suitable for different materials.
- 3 Select according to the shape of the head: The pentagonal head self tapping screw is more sturdy than the ordinary round head self tapping screw, but the price is also relatively high.
Frequently Asked Questions (FAQ)
Q What is the difference between coarse thread and fine thread self tapping screws?
Coarse thread self tapping screws have wider thread spacing and are better suited for softer materials such as wood and plastics, providing faster driving. Fine thread screws have closer thread spacing, offering stronger holding power in harder or denser materials like metal sheets.
Q What materials are galvanized self tapping screws suitable for?
Galvanized self tapping screws are suitable for a wide range of materials including thin metal sheets, wood, plastics, and composite boards. The galvanized coating provides excellent corrosion resistance, making them ideal for both indoor and outdoor applications.
Q How do I select the correct screw length and diameter?
The screw length should generally be 2.5 to 3 times the thickness of the material being fastened. The diameter should be chosen based on the material hardness — harder materials require a larger diameter for a secure hold. Refer to the thread specification table above for exact dimensions.
Q What is the advantage of a countersunk head self tapping screw?
Countersunk head self tapping screws sit flush with or below the surface of the material after installation, providing a clean and smooth finish. This makes them ideal for applications where a flat surface is required and where the screw head should not protrude.
Q What does the slot number in the specification table indicate?
The slot number refers to the Phillips (cruciform) drive size required to tighten the screw. A higher slot number corresponds to a larger drive size, which is matched to larger screw diameters to ensure proper torque transmission during installation.
Q What is the difference between Type C, Type F, and Type R point types?
Type C features a blunt point suitable for pre-drilled holes; Type F has a sharp gimlet point ideal for thin sheet metal without pre-drilling; Type R has a rounded point designed for use with soft materials. The "y" reference values in the table indicate the recommended point length for each type and screw size.