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Galvanized Countersunk Cross Tapping Screws - Quality China Suppliers & Factory for Reliable Installation
| 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
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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.
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2
Select by Thread Type Self tapping screws usually have two types: coarse thread and fine thread, and different threads are usually suitable for different materials.
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3
Select by Head Shape 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)
Q1
What is the difference between coarse thread and fine thread self tapping screws?
Coarse thread self tapping screws have wider thread spacing and are ideal for softer materials such as wood and plastic, providing strong grip. Fine thread screws have narrower spacing, offering better precision and are more suitable for harder materials like thin sheet metal.
Q2
What does the "ST" designation mean in self tapping screw sizing?
"ST" stands for "Self Tapping." The number following ST indicates the nominal outer diameter of the screw thread in millimeters, such as ST4.2 meaning a 4.2mm diameter self tapping screw. This helps users select the correct size for their application.
Q3
What are the differences between Type C, Type F, and Type R self tapping screws?
Type C has a blunt tip designed for use with pre-drilled holes in harder materials. Type F features a sharp, tapered point for cutting into softer materials without pre-drilling. Type R has a rounded point, offering a balance between the two and is commonly used in sheet metal applications.
Q4
Why are galvanized self tapping screws recommended for outdoor use?
Galvanized self tapping screws are coated with a layer of zinc, which provides excellent corrosion and rust resistance. This makes them highly suitable for outdoor environments, humid conditions, and applications where the screws may be exposed to moisture or chemicals over time.
Q5
How do I determine the correct length of a self tapping screw for my project?
As a general rule, the screw should penetrate at least 2–3 times its diameter into the base material for a secure hold. For example, an ST4.2 screw should have at least 8–12mm of thread engagement. Always consider the thickness of the material being fastened plus the required penetration depth.
Q6
What is the advantage of a countersunk head self tapping screw over a round head?
Countersunk head self tapping screws sit flush with or below the surface of the material once installed, providing a clean, smooth finish. This is especially useful in applications where a flat surface is required or where protruding screw heads could pose a safety or aesthetic concern.