What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In chemical production equipment, the cylinder body and the head cover need to be connected and sealed. The traditional sealing structure is to connect the two with a screw, add a non-metallic gasket in the middle and fix it with a nut. However, such a sealing structure only controls the tightening torque, and has the technical defect that the sealing ring will be twisted or even broken during repeated loading and unloading of the cylinder head cover, resulting in poor sealing performance.
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.
1. Standards for fastener product dimensions: specify the content of the basic dimensions of the product; threaded products also include the basic dimensions of the thread, thread end, shoulder distance, undercut and chamfer, and the end of externally threaded parts size, etc. 2. Standards for technical conditions of fastener products. It mainly includes product tolerances, mechanical properties, surface defects, surface treatment, product testing standards and corresponding specific provisions. 3. Standards for screw product acceptance inspection, marking and packaging: specify the qualified quality level and sampling plan of random inspection items during product acceptance inspection, as well as product marking methods and packaging requirements. 4. Marking method standards for standard parts, fasteners, screws and screws: specify the content of the complete marking method and simplified marking method of the product. 5. Standards for other aspects of fasteners: such as standards for fastener terminology, standards for fastener product weight, etc.
According to an aspect of Guangdong Yueluo Hardware Industry Co., Ltd., a rivet insertion mechanism is provided, including a pressure cylinder, a pressure shaft, an insertion nozzle, a bottom plate, a fixing block and a rivet fixing mechanism, wherein one end of the pressure shaft is connected with the pressure cylinder, and the other end is connected with the pressure cylinder. The insertion nozzle is connected, the fixing block is sleeved on the pressing shaft, and is fixedly connected with the bottom plate, the rivet fixing mechanism is installed on the bottom plate, and the insertion nozzle extends into the rivet fixing mechanism and can extend from the rivet fixing mechanism.
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