What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In many national standards, there will be a division of intensity levels. Combination screws are no exception. The strength grade of the combined screw is divided according to the material of the screw wire and the hardness index of the screw wire. General combination screw materials are divided into stainless steel and iron, stainless steel is divided into stainless steel 201, stainless steel 304 and stainless steel 316 and so on. Iron is divided into three types: low carbon steel, medium carbon steel, and high carbon steel. Carbon steel combination screws refer to iron combination screws. Generally, iron combination screws are classified into grades 4.8, 8.8, 10.9, and 12.9. However, the combination screws of grade 10.9 and grade 12.9 are rarely used in the market, so we will not talk about them here. And the combination screws on the market are more commonly used combination screws of grade 4.8 and 8.8. 4.8 grade combination screws are generally made of 1010A screw wire rods. After the screw wire rods are beaten into screws, they are combined with spring flat washers. After production, this 4.8 grade combination screw does not need to be hardened. Its hardness can reach 4.8. 8.8 grade combination screws are generally made of screw wire 10B21 piers. After the screw and wire piers are made into screws, they are equipped with spring washers and flat washers. They can pass through the automatic elastic flat washer machine to rub the three pieces together. Fasten the spring-flat washer combination on the screw, and the spring-flat washer will not fall off. After the combination screw is produced, it needs to be hardened to make the hardness reach 8.8. After the hardness reaches 8.8, we need to take it for electroplating. In order to prevent hydrogen embrittlement of the spring washer in the 8.8-level combination screw with added hardness, it is easy to break. In this way, we have to perform hydrogen removal treatment on the hardened combined screws, and only after the hydrogen removal can be plated. In short, there are many kinds of standard grades of combined screw strength, but generally only two types are used in the market, one is the 4.8-level combined screw strength, and the other is the 8.8-level combined screw strength. 4.8-level combination screws are the most used in the market and customer needs, and have a wide range of applications. As for the standard strength of 8.8-level combination screws, we generally refer to 8.8-level hexagon socket head combination screws, 8.8-level pan head combination screws, and 8.8-level external hexagon combination screws. These three are more commonly used.
Screws and nuts, as the most commonly used fastening devices, have the defect that they may loosen and fall off, especially those in a long-term vibrating environment are more likely to loosen and fall off. Additional anti-off parts such as anti-off washers and anti-off caps are added, so that an extra anti-off part is used in the fastening process, and these anti-off parts are sometimes difficult to find when they are not always needed and are inconvenient to use.
Traditionally used for plastic fastening screws, most of the thread designs are self-tapping threads, but for different plastic types, the self-tapping threads also have many different classifications, such as PT profile, Plastite series, Remform profile, etc. The structural parameters and manufacturing process of these threads are inconsistent, or require different main molds and wires. Therefore, to find a plastic screw that is universally applicable to various plastic types, has a single pressing structure, low-cost and simple manufacturing process, especially its special self-tapping thread, is an important issue that needs to be solved urgently at present. question. The purpose of Yueluo Yueluo Guangdong Yueluo Hardware Industry Co., Ltd. is to propose a plastic screw to solve the screw fastening problem that is generally applicable to different plastics. The purpose of Yueluo Guangdong Yueluo Hardware Industry Co., Ltd. is to realize a kind of plastic screw through the following technical scheme, it is characterized in that, the thread of the screw is composed of asymmetric threads with a profile angle of 30°, and the threads are The bottom surface of the connection between them is an arc surface. Yueluo preferably, the asymmetrical thread has a forward thread angle greater than the reverse thread angle, and the sum of the two-direction thread angles is 30°. Yueluo further preferred that the tooth profile angle of the asymmetrical thread is 20 degrees in the direction of installation, and the tooth profile angle in the reverse direction is 12 degrees. Yueluo Guangdong Yueluo Hardware Industry Co., Ltd.'s application of plastic screws, through the improvement of special thread structure, reduces the radial pressure and installation torque when the screw is installed, reduces the damage to the plastic hole; and increases the pull-out resistance of the screw force, it is not easy to appear loose assembly. At the same time, the design of the bottom surface of the connection between the threads of the arc optimizes the flow of the material of the installation object, which improves the integrity of the installation connection.
The spring screw is a tool that uses the physical and mathematical principles of the oblique circular rotation of the object and the frictional force to fasten the machine parts step by step; the screw is a common invention in people's production and life for thousands of years. According to the application field, Screws have a wide range of applications.
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