The classification of the second combination screw is divided according to the material of the screw wire and the hardness index of the screw wire. Generally, the two combination screws are divided into stainless steel and iron, and stainless steel is divided into stainless steel 201, stainless steel 304 and stainless steel 316. 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. But in the market, the combination screws of grade 10.9 and grade 12.9 are rarely used, so we won't talk about it here. And the two 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. The 8.8 grade combination screw is generally made of 10B21 screw wire. After the screw wire is punched into a screw, it is equipped with a spring washer and a flat washer, and the three pieces can be combined and rubbed by an automatic spring-flat washer machine. 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, it is necessary to carry out hydrogen removal treatment on the hardened combined screws, and the electroplating can only be done after the hydrogen removal.
Hexagon nuts are divided into three types: I type, II type and thin type according to the nominal thickness. Nuts above grade 8 are divided into two types: type 1 and type II. Type I hexagon nuts are the most widely used. Type 1 nuts are divided into three grades: A, B, and C. Among them, grade A and grade B nuts are suitable for machines, equipment and structures with small surface roughness and high precision requirements. Class C nuts are used on machines, equipment or structures with rough surfaces and low precision requirements.
In the production process of Yueluo, according to the different gap guarantee schemes adopted in the mold design, different gap assembly adjustment methods are adopted accordingly. At present, the gasket method, light transmission method, measurement method, copper plating (zinc) method are often used Method, coating method, process allowance, locator positioning and other assembly adjustment methods. Generally speaking, for the working parts processed separately by the punch and the concave die, since the reasonable gap of the die has been formed theoretically, the assembly principle is to fix the working part that is not easy to adjust, and adjust the working part of the other working part. To change the position between the punch and the die to ensure a uniform gap, at this time, only the screws are pre-tightened, and the positioning pins are not fixed. Yueluo, however, many years of practical experience have made those skilled in the art notice that if they can pay attention to the positioning pins and use the positioning pins in a targeted manner in the mold design or manufacturing process, they can often produce miraculous results with half the effort. Therefore, it is very important to design a positioning pin for a specific mold, which is of great practical significance.
Round head three-combination screws are also called pan-head three-combination screws, which are divided into large pan-head three-combination screws and small pan-head three-combination screws. The materials are divided into stainless steel and iron. The stainless steel round head three-combination screws include stainless steel small pan head three-combination screws and stainless steel large pan-head three-combination screws. The national standards are respectively expressed as GB9074.8 and GB9074.4.
Reference standard GB 90 Fastener acceptance inspection, marking and packaging GB 196 Basic dimensions of ordinary threads (1～600mm in diameter) GB 197 Tolerance and fit of ordinary threads (1～355mm in diameter) GB 230 Test method for Rockwell hardness of metals GB 699 High-quality carbon Plain structural steel technical conditions GB 1237 Marking method of fasteners GB 5267 Electroplating layer of threaded fasteners GB6394 Determination of average grain size of metals
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