Fine Thread Sheet Metal Screws

Fine thread sheet metal screws are used to connect low-strength light metal sheets such as aluminum alloys or magnesium alloys. Their fine pitch significantly reduces the stress concentration on the sheet during the tapping process. According to DIN 7500 stipulates the screwing performance of self-tapping screws. When using ST3.9 specification fine thread screws to perform tapping tests on a 2.0 mm thick 5052 aluminum alloy plate, the peak screwing torque is about 0.8 Nm, while the same diameter coarse thread screws reach 1.2 Nm, and the fine threads are reduced by about 10%. Thirty-three, this effectively avoids bulges or cracks in the thin plate during tapping. At the same time, the cutting depth of the fine thread is shallow, and the inner wall of the plate is less scraped. The effective meshing area after thread formation reaches more than 92% of the standard value, so that stable pull-out resistance can be obtained under lighter tightening force. This feature is especially suitable for precision assembly occasions that have strict requirements on material integrity and appearance, such as notebook casings, mobile phone middle frames, and LED lamp heat sinks.

 

 

In terms of installation torque and pre-tightening force control, fine-thread thin plate screws have a smaller thread rise angle and have a more significant frictional self-locking effect. However, the thickness of surface coatings such as zinc-chromium film will significantly affect the torque coefficient. According to the VDI 2230 systematic calculation criteria, when the coating thickness is controlled at six to ten microns, the friction coefficient between the screw and the bearing surface of the aluminum alloy base material is about 0.14 to 0.20. When tightened to the recommended standard torque of 2.2 Nm, the corresponding axial preload force can stably reach 2,200 N. After the lateral vibration test, according to DIN 267 Part 26 method, the residual pretightening force still maintains 89% of the initial value after 200 vibration cycles, which is higher than 73% of the coarse thread screw of the same size.

 

 

This high retention rate is due to the denser thread contact lines of fine threads, which can effectively disperse shear stress and resist micro-displacement. At the same time, it is recommended to use a pneumatic screwdriver with a depth limit during the installation process to avoid thread seizure or head breakage caused by over-torque. This makes fine-thread thin-plate screws an ideal choice for balancing connection strength and assembly convenience in structures that are subject to long-term dynamic loads, such as car seat frames, instrument brackets, and household appliance chassis.

 

 

 

 

 

 

Obtain drawings from customers or create drawings based on their specifications or samples.

The drawings, product raw materials, surface treatment, and other details are attested to by both parties.

 

 

 

 

Provide a quote, confirm the order quantity, and include all relevant information.

Like the terms of payment, the terms of trade, the kind of packaging, etc.

 

 

 

When manufacturing the goods, adhere precisely to the original drawings and samples.

After a final inspection, it was meticulously packaged and delivered to the customers.

 

 

 

 

 

 

 

 

 

 

 

 

 

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