This article does not cover the materials of tapping screws, but only introduces their standards and characteristics.
During installation of tapping screws, the driving torque into the base material is the key technical requirement, which relates to parameters such as the diameter of the pilot hole and the thread length of the tapping screw. Different pilot hole sizes and thread lengths result in different friction and locking torques during installation. As the tapping screw is continuously driven into the base material, its torque value changes constantly, reaching the maximum when the screw is at the optimal installation position. Normally, if tightened manually with an ordinary screwdriver, the reference point is when it can no longer be turned. However, since individual strength varies, it is better to use power tools with torque adjustment.
Tapping screws also have a breaking torque, which refers to the torque at which the screw twists and breaks directly. Comparing these two different torque parameters: the smaller the driving torque, the better; the larger the breaking torque, the better. The greater the difference between these two values, the better the performance and installation reliability of the tapping screw.
Tapping screws are usually used in large quantities because they are applied in groups or batches. Many plastic components have densely arranged pilot holes, since one or just a few tapping screws cannot ensure anti-loosening performance. After all, tapping screws only achieve locking through friction between the threads and the base material, which is less effective than the traditional bolt-nut locking method. Therefore, tapping screws are usually installed in groups rather than individually on the same base material. To ensure even stress distribution, designers usually reduce the number of screw sizes and use only one standard size as much as possible. This ensures the flatness of the overall structure, allows reasonable space layout, and guarantees installation accuracy.
The main difference between tapping screws and machine screws lies in the thread design. Tapping screws have a larger thread pitch and higher thread profile than machine screws. With the same pilot hole, driving in a machine screw may crack the plastic base material, while a tapping screw will not. This is because tapping screws have sharp threads that can drill directly into the base material without excessive expansion.
Tapping screws are also easier to install than machine screws. Machine screws require matching nuts, taking longer to install and costing more. Tapping screws only need to be driven into place with a tool, usually in just a few seconds.
Machine screws generally have a uniform thread end type, while tapping screws have three different standards.The first is the most common pointed tapping screw, corresponding to national standards GB/T 845 and GB/T 846 based on head style.The second is the flat-end tapping screw, which can be specified simply by adding "flat end" to the standard description.The third is the thread-cutting tapping screw, which has a slot milled at the end of the threads.The appropriate tapping screw standard can be selected according to different application environments.
