A self-tapping screw is a screw that can tap its own threads in softer materials. In the case of softer materials, it does not need to pre-drill holes in the material, and by virtue of its own sharp and deeper threads, it cuts into the material (e.g., wood, plastic, thin sheet metal, etc.) by rotating it, thereby forming a matching internal thread and realizing the fixing effect.
The self-drilling screw is more versatile than the self-tapping screw. It comes with a drill-like structure, not only can tapping, but also can be drilled in hard materials (such as thick steel plate, aluminum alloy, etc.), and then synchronized to complete the tapping operation. It can be said that self-drilling screws combine drilling and tapping functions in one, which is an efficient fastener in the industrial field.
To quickly distinguish self-drilling screws from self-tapping screws, you can observe their appearance and structure. The tip of a self-tapping screw is usually tapered or flat-ended, with no drilling structure, and the threads start directly underneath the head. It relies heavily on the sharp threads to squeeze and cut into the material for tapping and fixing.
Self-drilling screws have a helical bit-shaped tip with a drill-like cutting edge, and the threads start at the back of the bit. When in use, its tip can first cut the material to form a hole, and then the threads follow the tapping, this structure gives it the ability to drill holes.
Self-tapping screws it requires the material itself to be softer, or have a small hole in advance. For example, in plastic parts, self-tapping screws by rotating the threads to squeeze the material, forcing the material to form internal threads; if used for thin metal plates, you may need to first play a guide hole smaller than the diameter of the screw, otherwise it is easy to cause the material to crack. Self-drilling screws do not need to be pre-drilled, and can directly realize the “drill + tap” all-in-one operation. When facing thick steel plate (such as iron plate above 3mm), its drill tip first rotates and cuts out the hole, then the thread follows up and taps out the matching threads on the inner wall of the hole, the whole process does not need to change the tool, which greatly improves the working efficiency.
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