Development history and selection of self-tapping screws
Development history of self-tapping screws:
Since 1914, self-tapping screws have been commercialized. The previous design-mainly from wood screws-is a carburized steel tapered tail A-type thread forming screw. The main purpose at that time was to join the iron skin on the duct of the air conditioning system Therefore, it is also called metal screw. After more than 80 years of development, it can be divided into four periods-thread forming, thread cutting, thread rolling and self-drilling.
Thread forming self-tapping screws:
(Thread Forming Tapping Screws)─It is directly developed from metal screws. Thread forming self-tapping screws must be pre-drilled before use, and then the screws are screwed into the holes, which are strongly extruded to fit the female threads. The material will be squeezed between the male threads, which is called a thread forming self-tapping screw. It can only be applied to thin and plastic materials, so it has been developed; Thread Cutting Tapping Screws ─ in the thread One or more cutting holes are cut at the tail end, so that when screwing into the pre-drilled hole, the screw tail and teeth are used to cut the matching female thread in a similar way to the tap. It can be used in thick plates, which is relatively hard Or fragile materials that are not easy to shape.
Thread rolled into self-tapping screws:
(Thread Rolling Tapping Screws)─Triangular self-tapping screws, also known as Type TT (Type Tai is still available***) is developed based on the principle of forming screw taps, and the thread rolling into self-tapping screws has specially designed threads And the end allows the screw to roll into a matching female thread under intermittent pressure. At the same time, the material around the hole can more easily fill the space of the thread and bottom of the self-tapping screw, because its friction force is more self-tapping than the thread forming The screw is small, so it can be used on thicker materials, the torque required for rotation is better controlled, and the strength is higher after the combination. The engineering standard of thread rolling into self-tapping screws is better than that of forming or cutting self-tapping screws. Heat treatment, the definition of strength is higher and more clear, making the thread rolled into a self-tapping screw become a real "construction" fastener.
screw wood do much less damage to wood and are easier to remove and even be reused. More and more widely used in wood,instead of wood screw,metal,all kinds of board.
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