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China Galvanized Countersunk Cross Tapping Screws - Reliable Suppliers and Factory for Quality Fasteners
| 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.
FAQ
Frequently Asked Questions
QWhat are galvanized countersunk cross tapping screws typically used for?
Galvanized countersunk cross tapping screws are widely used for fastening thin metal sheets, wood, and plastic. The countersunk head sits flush with the surface, making them ideal for roofing panels, HVAC ductwork, electrical enclosures, and general sheet metal assembly where a clean, flush finish is required.
QWhat is the difference between coarse thread and fine thread self-tapping screws?
Coarse thread screws have fewer threads per inch and penetrate faster, making them better suited for softer materials like wood and plastic. Fine thread screws engage more gradually and provide greater holding strength in harder, thinner materials such as steel sheet — where stripping is a concern and precision matters.
QWhat is the difference between Type C, Type F, and Type R self-tapping screws?
Type C features a blunt point designed for heavier-gauge metal. Type F has a sharp, tapered point with cutting flutes, optimized for thinner sheet metal where precise thread forming is needed. Type R uses a finer pitch and a sharp point, suitable for soft metals and plastics. The reference values (y) in the specification table indicate the minimum material engagement depth for each type.
QWhy choose galvanized self-tapping screws over non-galvanized ones?
The zinc galvanizing layer acts as a sacrificial barrier against rust and oxidation, significantly extending the screw's service life in outdoor, humid, or chemically exposed environments. Non-galvanized screws will corrode much faster in similar conditions, potentially compromising the structural integrity of the connection over time.
QHow do I select the correct thread diameter (ST size) for my project?
Refer to the specification table and consider the material thickness, required pull-out strength, and pilot hole size. Thicker or harder materials generally require a larger diameter (e.g., ST4.8 to ST6.3 or above). Match the pitch and head dimensions (dk, k) to the load requirements and countersink geometry of your application for optimal performance.
QCan self-tapping screws be removed and reused?
Self-tapping screws are generally not designed for repeated reuse. Because they cut their own threads on first installation, removing and reinserting the same screw into the same hole risks stripping the formed threads and weakening the joint. If reinstallation is needed, use a slightly larger diameter screw or install a thread insert into the original hole to restore holding strength.