What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Screws are a kind of fasteners commonly used in machinery, but most of the screws commonly used in the market are standard parts. The screws themselves are ordinary and have no function of preventing loosening and protecting the matrix. Therefore, in order to prevent the screws from loosening during use , Usually it is necessary to configure additional elastic washers, flat washers, etc. that are suitable for screws, and these elastic washers and flat washers are mostly metal products. During use, it is easy to wear with the body base and damage the protection of the sheet metal base. After long-term use, metal washers are easy to rust, which affects the tightening effect and appearance of screws. In addition, the use of metal washers not only increases the weight and cost, but also the assembly process is complicated and cumbersome, and the anti-loosening and anti-wear effects are not ideal. .
Many existing products need to use screws in the production process, especially in the field of nuclear power sluice gates, it is necessary to fill a part of the sluice gate with screws to fix the size and structure. If the fixing effect is not good, then It will lead to more leakage of water gates, waste a lot of water resources, and even cause safety accidents.
China is the world's largest producer of carbon steel fasteners such as screws, nuts and bolts, and the EU is a major market for these products. In January 2009, the EU decided to impose anti-dumping duties of 26.5% to 85% on Chinese carbon steel fastener products. On July 31 of the same year, China resorted to the relevant EU legislation and anti-dumping measures to the WTO dispute settlement mechanism. The case became China's first lawsuit against the EU at the WTO. On July 15, 2011, the WTO Appellate Body issued a report and finally ruled that China won the case in the trade dispute with the European Union on fasteners. The head of the Department of Treaty and Law of the Ministry of Commerce of China welcomed the ruling on the 16th, and said that China's victory in the case is of great significance, which will help improve the competitive environment for Chinese companies in the international market including the European Union, and will also strengthen the WTO members' interest in the case. Confidence in WTO rules and the multilateral trading system. This is not only a victory for China's industry, but also a victory for WTO rules, the official said. The WTO Appellate Body found in its ruling report issued on the 15th that Article 9(5) of the EU's Basic Anti-dumping Regulations on individual tax rates violated WTO rules; at the same time, the Appellate Body overturned some of the panel's rulings and supported China's position , ruled that the EU's anti-dumping measures against Chinese screws, nuts, bolts and other carbon steel fasteners also violated WTO rules in terms of domestic industry identification, normal value and fair comparison of export prices. The head of the Treaty and Law Department of the Ministry of Commerce of China said that the EU is one of the WTO members that has initiated the most anti-dumping investigations against Chinese products in the world. unfair treatment. He said that China hopes that the EU will cancel the legislation and discriminatory anti-dumping measures that are inconsistent with WTO rules as soon as possible, treat Chinese export enterprises fairly, and effectively safeguard free trade and fair competition.
(1) The surface rust, oil stains, burrs on the wall of the bolt holes, welding flashes, etc. should be cleaned up. (2) After the contact friction surface is treated, the specified anti-scratch coefficient requirements must be met. The high-strength bolts used should have matching nuts and washers, which should be used in accordance with the matching and should not be interchanged. (3) When the friction surface of the treated component is installed, it is not allowed to be stained with oil, soil and other sundries. (4) The friction surface of the module should be kept dry during installation and should not be operated in the rain. (5) Strictly check and correct the deformation of the connected steel plates before installation. (6) It is forbidden to hammer into the bolt during installation to prevent damage to the bolt thread. (7) The electric wrench, which is regularly tested during use, ensures the accuracy of the torque and operates in the correct tightening sequence. Main safety technical measures (1) The size of the wrench of the adjustable wrench should be consistent with the size of the nut, and the sleeve should not be added to the small wrench. A dead wrench should be used for high-altitude work. For example, when using an adjustable wrench, use a rope to fasten it, and people should fasten their seat belts. (2) When assembling the connecting bolts of steel components, it is strictly forbidden to insert your hands into the connecting surface or touch the screw holes. When picking and placing the bolster, your fingers should be placed on both sides of the bolster.
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