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Thread knowledge of fasteners

Update:30-04-2021
Summary:

How does the screw thread come from? In the production […]

How does the screw thread come from? In the production process, the shape of the screw is usually punched first. This is what we call the head in the screw industry. After that, the screw threads are rubbed, which is what we often call thread rubbing. Or called thread rolling. After the teeth are rubbed, they become natural screws. Natural screws, such as iron screws, generally need electroplating.

On the section passing through the thread axis of the screw, the profile shape of the thread is called the tooth profile. The angle between the two adjacent flanks is called the profile angle. Commonly used common thread has a triangular profile with a profile angle of 60°. The major diameter refers to the diameter of an imaginary cylindrical or tapered surface that coincides with the crest of the external thread and the bottom of the internal thread. The major diameter of the external thread is represented by d, and the major diameter of the internal thread is represented by D. The minor diameter refers to the diameter of an imaginary cylindrical or tapered surface that coincides with the root of the external thread and the crest of the internal thread. The minor diameter of the external thread is represented by d1, and the minor diameter of the internal thread is represented by D1. Between the major diameter and the minor diameter, imagine a cylindrical surface (or conical surface). In its axial section, the tooth width and groove width on the plain line are equal, then the diameter of the imaginary cylindrical surface is called the pitch diameter, and d2( Or D2). Line number: The number of spiral lines forming a thread is called the line number. There are single-thread and multi-thread threads. Multi-thread threads are evenly distributed in a section perpendicular to the axis. Lead The axial distance between two adjacent teeth on the pitch line corresponding to two points is called the pitch.

On the same spiral line, the axial distance between two adjacent teeth corresponding to two points on the median diameter line is called the lead. The relationship between the number of threads n, the pitch P, and the lead S is: S=n·P Rotation direction When viewed along the axis, a thread that rotates clockwise becomes a right-hand thread, and a thread that rotates counterclockwise is called a left-hand thread. The thread profile, major diameter, pitch, number of threads and direction of rotation are called the five elements of thread. Only the internal and external threads with the same five elements can be screwed together. It is very important for the screw itself, and it is also very important for the product that needs the screw. The screw itself refers to the quality of the screw. For products that use hardware screws, this is related to the quality of the screw thread, whether it can be used on the product, whether the thread can be driven into the product or the nut can be twisted. Generally speaking, the screws we produce need to pass through and stop regulations. It means that the rules must be passed, and the rules must be stopped.

The screw thread is extremely important to the quality of the screw. If the screw thread can not pass the pass and stop rules and cannot meet the customer's requirements, then this screw is not an excellent screw. Some customers have relatively high requirements for screw threads, and generally need to pass through and stop regulations. But some customers don't need it. But in general, if you want to use the screw with the nut, you generally need to pass the stop rule.
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