Non-standard screw(https://www.yyjfhardware.com/product […]
Non-standard screw(https://www.yyjfhardware.com/product/nonstandard-screw/) production, metric thread is based on MM (millimeter) as the unit, and its cusp angle is 60 degrees. Both American and British threads are measured in inches. The cusp angle of American threads is also 60 degrees, while the cusp angle of British threads is 55 degrees. Due to the different measurement units, the representation methods of various threads are different. For example, M16-2X60 means a metric thread, which means that the nominal diameter of the screw is 16MM, the pitch is 2MM, and the length is 60MM. Another example: 1/4-20X3/4 means inch threads, which means the screw The nominal diameter is 1/4 inch (one inch = 25.4MM), there are 20 teeth on one inch, and the length is 3/4 inch. In addition, to indicate American screws, UNC and UNF are usually added after the British screws to distinguish between American coarse threads and American fine threads.
The specifications of the fixing screws used for each material are different, but there are some basic rules:
(1) There are many types of screw heads and grooves, which are generally different according to appearance and tamper resistance, or other requirements. This is relatively intuitive.
(2) There are three types of screw pitch: machine teeth, plastic screws, wood screws or wall screws. The screw pitch is mainly related to the density of the material to be locked. The higher the material density, the smaller the pitch. The pitch of the plastic screws can also be different. For example, the pitch of soft materials such as PP and PE can be increased, so that it is not easy to slip; while the denser materials such as POM and PC can use screws with a smaller pitch. Coarse teeth in machine teeth refer to standard screws used in ordinary occasions; fine teeth can have different pitches according to different requirements, and they also refer to non-standard screws, which are used in special occasions.
(3) The shape of the screw tail is more complicated. However, the more common ones we use are flat tail, pointed tail, grooved, triangular, cone and so on. These shapes have several functions: positioning, tin transfer, self-tapping, self-locking and other functions. Different tail requirements can be selected according to the function.