VÍT TỰ KHOAN

Strength of Self-Drilling Screws 

Axial tensile strength: the axial tensile strength of self-drilling screws depends on many factors, including its material, thread design and anchorage after drilling into the material. Generally speaking, self-drilling screws are made of carbon steel, stainless steel and other materials. For example, high-quality carbon steel self-drilling screws can withstand a certain degree of axial tension after drilling into metal plates. In the field of architecture, when used to fix the color steel plate on the roof, the self-drilling screws with normal specifications can withstand large wind suction. If it is screwed into a metal plate with appropriate thickness according to the correct installation process (such as 0.61.0mm thick color steel plate), it can resist the wind suction of at least 1.01.5kN per square meter and ensure that the color steel plate will not be lifted under normal wind conditions.

Shear strength: the shear strength of self-drilling screws is also very important to ensure the stability of the connection structure. Its shear strength is related to the diameter and material of the screw and the friction between the thread and the connected material. In automobile manufacturing, self-drilling screws are used to fix some thin plate structures in non-critical parts, such as the fixing of automobile interior panels. When the vehicle is subjected to vibration, collision, etc. during driving, these self-drilling screws can bear a certain shear force at the joint. Taking a self-drilling screw with a diameter of 4mm as an example, the shear strength can reach about 35kN in the connection of suitable materials (such as fixing plastic interior panels and thin metal brackets), which effectively prevents the interior panels from shifting due to external force.

Durability of Self-Drilling Screws 

Corrosion resistance: If the self-drilling screw is made of stainless steel, it has good corrosion resistance. For example, 304 stainless steel self-drilling screws can be used for many years without rusting in general outdoor environment (such as environment with high humidity and a little acid rain). This is because stainless steel contains alloying elements such as chromium, which can form a dense oxide film on the surface to prevent oxygen and moisture from further corroding the screw. In the building facilities in coastal areas, such as the awning on the seashore and the simple railing of the wharf, the use of stainless steel self-drilling screws can effectively resist the corrosion caused by seawater and sea breeze.

Wear resistance: the wear resistance of self-drilling screws is mainly reflected in its drill tip and thread part. Because the drill tip will rub with the material when drilling into it, it needs good wear resistance. The drill tips of many self-drilling screws are made of cemented carbide, which has high hardness and good wear resistance. In the industrial environment where self-drilling screws are frequently used, such as the prefabrication factory of steel structure, even if they are installed and used for many times, their drill tips can maintain a good sharpness and can effectively penetrate materials. At the same time, the wear resistance of the thread is also very important. Good thread wear resistance design can ensure that the thread will not be damaged by vibration, friction and other factors during long-term use, thus ensuring the fastening of the connection. For example, the thread self-drilling screw with special surface treatment (such as hard chromium plating) will obviously reduce the thread wear speed and prolong its service life by about 30% to 50% in the connection environment with certain friction (such as the connection between wood and metal).

Anti-loosening performance: after drilling into the material, the thread of the self-drilling screw is closely combined with the material, which has good anti-loosening performance. Especially in the environment with vibration, such as fixing the shell of mechanical equipment, installing the outdoor unit of air conditioner, etc. In these application scenarios, self-drilling screws can keep the connection relatively stable under long-term vibration environment through the friction between their own threads and materials and possible mechanical occlusion. Some self-drilling screws will also adopt special anti-loosening design, such as adding nylon washers or using coatings with thread locking agents to further improve their anti-loosening performance and make the connection structure durable and reliable under complex working conditions.