Self-tapping screws

Although self-tapping screws have been used for a long time, they generally know how to make them. However, the standards and requirements stipulated in each specification may not be very clear. Here, only by collecting the specifications, a suitable reading is made for everyone. Can have a little more understanding of self-tapping screws.
Self-tapping screws are threaded fasteners that are self-tapping in the pre-drilled holes of metal or non-metal materials.
High-strength, single-piece, single-sided combination. Due to its self-forming or tapping its matching thread, it has high anti-loose ability in combination and can be loaded and unloaded. Its size, thread type and head on small screws Type and tapping performance are almost limitless in engineering applications.

1Evolution: Since the self-tapping screws began commercialization in 1914. The first design - mainly from wood screws - is a genus
    Carburized steel taper tail A-type thread forming screw. The main purpose at that time was to use the iron joint on the air conditioning system conduit, so
    Also known as the tin screw. After more than 80 years of development, it can be divided into four periods - thread forming, thread cutting, thread rolling
    Cheng and self-drilling.
Thread Forming Tapping Screws - developed directly from metal screws, threaded into
    Type self-tapping screws must be pre-drilled, then screw into the hole, strongly extruded with the female thread, and the original thread
    The material in the position will be squeezed between the male threads, which is called a thread-formed self-tapping screw. It can only be used for thin and plastic
    The material of sex has therefore developed.
Thread Cutting Tapping Screws - cutting one or more cuts at the end of the thread
    The mouth enables the use of the screw tail and the tooth to cut out the matching female thread when screwing into the pre-drilled hole.
    Can be used on thick plates, relatively hard or fragile materials that are not easy to shape.
Thread Rolling Tapping Screws - Triangle Self-tapping Screws, also known as Type TT (Type
    Tai is still patented. It is based on the principle of forming screw tapping. The thread is rolled into a self-tapping screw with special design.
    The thread and the end of the thread allow the screw to roll itself into a mating female thread under intermittent pressure. At the same time the material around the hole
    It is easier to fill the space of the self-tapping screw thread and the bottom of the tooth, because the friction force is smaller than the thread forming self-tapping screw.
    Therefore, it is possible to use the torque required for the rotation on a thicker material, and the strength is higher after the combination.
    The engineering standard definition of tapping screws is higher than the definition of material, heat treatment and strength of forming or cutting self-tapping screws.
    Clearly, the thread is rolled into a self-tapping screw to become a true "construction" fastener.
Self Drilling Tapping Screws - also known as Tec, the most expensive in all processes of assembling self-tapping screws
    The cost is the preparation of the pre-drilling. The use of self-tapping screws must be drilled first. The aperture must also be limited. No pre-drilling is required.
    In some respects, it can save costs. This is the drill tap, tapping, and tightening the self-tapping screws at the end of the drill.
    The surface hardness and core hardness are a little higher than the general self-tapping screws, because the drilling screw has one more drilling operation.
    In addition, the drill-end screw is still required to pass through the test, and the test screw can drill and break the thread within a specified time.
The above are the design and development process of the four main self-tapping screws, and two other screws designed for special threads, the first one is;
High – Low Tapping Screws – used in plastic or other low density materials. Double thread design,
    High thread (larger outer diameter of the tooth) has a flatter and sharper thread angle of 30 degrees. Low thread (outer diameter of the tooth)
    Small) has a thread angle of 60 degrees, the height of the teeth is only half of the high thread. The combination of high and low threads reduces the rotational torque.
    Improved pull-out strength and greatly reduced the risk of broken joints. Another used drywall in the construction industry (Drywall)
    For self-tapping screws with such thread design, it is especially suitable for plastics, parts plates and wood. The other is;
Twin Lead Self Drilling Point Tapping Screws - When assembling
    It is easy to screw into the dry wall, drill a hole in the steel bar and tap the matching female thread. The horn has a concave receiving surface.
    To prevent damage to the wallpaper or plaster surface when screwing in.
Most self-tapping screws are commercially available, for example when self-tapping screws are supplied with a combination screw (SEMS)
For tighter service. Screws with special design for thick and thin threads focus on anti-loose after assembly.

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