What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
At present, with the development of my country's railway industry, many railway fastener systems involve T-bolts. The structure is shown in Figure 1. The dimensions that need to be inspected are head width A, head length B, and head straight table height. C. The height of the head slope D, the total length of the bolt E, and the major diameter of the bolt F. Due to the irregular shape of these places to be inspected, the measurement is difficult. The measurement of general measuring tools is not only slow, but also difficult to control human errors, resulting in some extreme upper limits and There are disputes and misjudgments about the size of the extreme lower limit when judging qualified and unqualified.
Iron pans are traditional kitchen utensils for people to cook food. They generally do not contain toxic substances and will not oxidize. In the process of stir-frying and cooking food, there are very few dissolved substances in the iron pot. Even if there is iron dissolved out, it is also good for the human body. Cooking in the iron pot is the most direct way to supplement iron. The main types are India pot, ear pot, pan, oil pan, pancake pan. In the process of cooking dishes in an iron pan, a small amount of iron will dissolve in the food, supplement iron for people, supplement the iron-deficient part of the food itself, and play a role in preventing iron-deficiency anemia. Can increase the amount of iron in a person's diet. Therefore, as far as the prevention and treatment of iron deficiency anemia is concerned, cooking in an iron pan is beneficial to health.
High-strength bolt connection has the advantages of simple construction, good mechanical performance, disassembly and replacement, fatigue resistance, and no loosening under dynamic load. It is a promising connection method. High-strength bolts use a special wrench to tighten the nut, so that the bolt generates a huge and controlled pre-tension. Under the action of pre-pressure, a large frictional force will be generated along the surface of the connected parts. Obviously, as long as the axial force is less than this frictional force, the components will not slip and the connection will not be damaged. This is the high-strength bolt connection. principle. High-strength bolted connections rely on the friction between the contact surfaces of the connectors to prevent them from sliding each other. In order to make the contact surfaces have sufficient friction, it is necessary to increase the clamping force of the components and increase the friction coefficient of the contact surfaces of the components. The clamping force between the components is achieved by applying pretension to the bolts, so the bolts must be made of high-strength steel, which is why it is called high-strength bolted connections. In high-strength bolted connections, the friction coefficient has a great influence on the bearing capacity. Tests show that the coefficient of friction is mainly affected by the form of the contact surface and the material of the components. In order to increase the friction coefficient of the contact surface, methods such as sandblasting and wire brush cleaning are often used to treat the contact surface of the components within the connection range during construction.
Before the special vehicle is refitted, the chassis and the car frame should be reinforced again, and the fastened part of the rivets should be disassembled before the car frame is reinforced.
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