What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Currently, the method of fixing objects on cement is with cement nails or expansion screws. Cement nails are objects made of hard alloy steel that look like iron nails, which are composed of nail tips and nail bodies. Cement nails are hammered into the cement. Cement nails are easy to drive in, but not removable. The expansion screw is composed of a large end screw, a slotted sleeve, a gasket, a spring washer, and a nut. When using, first drill a hole in the cement with an electric hammer, put in the expansion screw, and tighten the nut to make the slotted sleeve expand at the tail of the big tail screw, so as to fix the expansion screw on the cement. At this time, unscrew the nut to install a fixed object on the expansion screw. Although this method can be disassembled, an electric hammer is required for the first installation, which is inconvenient.
The flat washer is mainly used to reduce the pressure. When some parts are tightened with a large axial force, it is easy to press the washer into a dish shape. At this time, it can be solved by changing the material and increasing the hardness.
Various stainless steel materials have different properties due to their different material contents, so the corrosion resistance is also different. The following is a brief explanation of several commonly used materials: 304 is a universal stainless steel, which is widely used in the production of good requirements. Equipment and components with comprehensive properties (corrosion resistance and formability). 301 stainless steel exhibits obvious work hardening phenomenon during deformation, and is used in various occasions requiring higher strength. 302 stainless steel is essentially a variant of 304 stainless steel with higher carbon content, which can obtain higher strength by cold rolling. 302B is a kind of stainless steel with high silicon content, which has high resistance to high temperature oxidation. 303 and 303Se are free-cutting stainless steels containing sulfur and selenium, respectively, and are used in applications where free-cutting and high surface finish are mainly required. 303Se stainless steel is also used to make parts that require hot upsetting, because under these conditions, this stainless steel has good hot workability. 304L is a lower carbon variant of 304 stainless steel used where welding is required. The lower carbon content minimizes carbide precipitation in the heat-affected zone near the weld, which can lead to intergranular corrosion (weld erosion) of stainless steel in some environments. 304N is a nitrogen-containing stainless steel, and nitrogen is added to increase the strength of the steel. 316 (18Cr-12Ni-2.5Mo) material: due to the addition of Mo, its corrosion resistance, atmospheric corrosion resistance and high temperature strength are particularly good, and can be used under harsh conditions; excellent work hardening (non-magnetic).
As an important connecting part in the automobile assembly process, the screw plays a vital role in the safety performance of the automobile. The assembly of each component of the vehicle cannot be separated from the function of the screw. In the connection of the automobile assembly and its parts, the screw connection As well as simple structure, easy maintenance and disassembly, it is widely used. There may be thousands of screws on a car. The screw connection of each part has its own function and function. Once one or some screw connections fail, it will be It will lead to the loosening or even separation of the connected parts. If the car is running, it is likely to cause some parts to fail or break away. The light ones will cause the main functions of the car such as steering and braking to fail, potentially affecting driving safety. If it is not found in time, it will lead to major safety accidents and even endanger the lives of people. The failure of the car screws will cause the safety hazard of the whole vehicle, and will also cause customers to worry and complain, thus affecting the reputation of the company and endangering the life of the company. cycle.
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