Machining black nickel round head with pad with self-tapping screw with tapping PWA 3/4

screw with a gasket includes a screw head and a screw connection part connected with the screw head, the screw connection part is provided with a thread, and a transition part is provided between the screw head and the thread provided on the screw connection part , the diameter of the transition part is smaller than the diameter of the thread, the transition part is sleeved with a plastic washer, the inner ring of the plastic washer is a polygon, and the diameter of the inscribed circle of the inner ring of the plastic washer is smaller than the diameter of the thread. The utility model replaces the traditional metal washer with a plastic washer, which avoids the phenomenon that the washer causes wear on the connection base. The inner hole of the plastic washer adopts a polygonal design, and the diameter of the inscribed circle of the inner ring of the plastic washer is smaller than the diameter of the thread, which is in the same shape as the thread. The multi-point contact solves the problem that the washer is easy to slip off due to the circular design of the inner hole of the traditional metal washer, and improves the assembly efficiency of the screw.

Usually, the car wheel is fixed on the axle sleeve with positioning pins and pins, and the tire hub and the sleeve are fastened on the axle with locking nuts, lock washers, and adjusting nuts. This structure can operate normally within a certain period of time when the vehicle speed is low and the vibration is small. However, when the car runs for a long time, especially when the road surface is uneven and the load changes sharply, the axle sleeve bears a great impact. Once the shear force generated is too large, the pin will break, and the nut will be loosened. Affected, the wheel and hub will be loose. If the maintenance is not timely, or the driver is inexperienced, the car will have an accident in which the tire falls off with the wheel hub. This is extremely dangerous. So people are looking for ways to prevent wheels and hubs from falling off

safety screw includes a screw rod, and is characterized in that: the two ends of the screw rod are respectively provided with notches for rotating a tool knife. Compared with the prior art, the advantage of Guangdong Yueluo Hardware Industry Co., Ltd. is that notches are provided at both ends of the screw, so that when the screw is in use, it can be tightened or loosened from both ends without installation. Due to the limitation of position and structure, when the installation space is small or the tool knife cannot be inserted, it is convenient for the operator to directly tighten or loosen the screw from the other end, which improves the efficiency of installation and disassembly, saves assembly time and reduces assembly difficulty.

When the countersunk head screws and hexagon socket head bolts are produced by the cold heading process, the original structure of the steel will directly affect the forming ability of the cold heading process. In the process of cold heading, the plastic deformation of the local area can reach 60%-80%, so the steel must have good plasticity. When the chemical composition of the steel is constant, the metallographic structure is the key factor to determine the plasticity. It is generally believed that the coarse flaky pearlite is not conducive to cold heading forming, while the fine spherical pearlite can significantly improve the plastic deformation ability of the steel. For medium carbon steel and medium carbon alloy steel with a large amount of high-strength bolts, spheroidizing (softening) annealing is performed before cold heading, so as to obtain uniform and fine spheroidized pearlite to better meet the actual production needs. For the softening annealing of medium carbon steel wire rods, the heating temperature should be kept above and below the critical point of the steel, and the heating temperature should not be too high, otherwise tertiary cementite will precipitate along the grain boundary, resulting in cold heading cracking. The wire rod of medium carbon alloy steel is annealed by isothermal spheroidization. After heating at AC1+ (20-30%), the furnace is cooled to slightly lower than Ar1, the temperature is about 700 degrees Celsius for an isothermal period, and then the furnace is cooled to about 500 degrees Celsius and air-cooled. The metallographic structure of the steel changes from coarse to fine, from flake to spherical, and the cracking rate of cold heading will be greatly reduced. The general area of softening annealing temperature for 35\45\ML35\SWRCH35K steel is 715-735 degrees Celsius; while the general heating temperature for spheroidizing annealing of SCM435\40Cr\SCR435 steel is 740-770 degrees Celsius, and the isothermal temperature is 680-700 degrees Celsius.

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