What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The lifting ring screws are generally not surface treated, but according to the requirements, surface treatment such as galvanized passivation and chrome plating can be carried out, and it is specified in GB5267-85. The chemical composition and mechanical properties of the material should be treated immediately after electro-galvanizing. The test methods are specified in GB699. During routine inspection, the grain size test may not be advanced, and the grain size test method shall be in accordance with the provisions of YB27. Thread inspection is performed with thread gauges and smooth limit gauges or universal energy tools.
screw is a type of fastener that cooperates with threaded holes for combining various parts into one assembly and making the parts easy to assemble or disassemble. However, when the assembly containing the screw is used in a special environment, such as outdoor use or use in a liquid environment, there are requirements for preventing the leakage of liquid through the screw joint and preventing the screw from loosening at the screw joint. The screw structure does not have such a function. In the prior art, when there is a need for leakage prevention and loosening of the screw, a rubber washer is usually added between the screw head of the screw and the locking surface of the locked part, or the thread part of the screw is wrapped to prevent Leakage tape and then add anti-loose washers between the screw head of the screw and the locking surface of the locked part, so as to achieve the purpose of preventing leakage and loosening. However, the use of washers not only increases the thickness and weight of the assembly, but also requires an additional process during assembly, which is labor-consuming and labor-intensive. In the process of screwing, it is easy to cause uncertainty to the rubber washers due to the shear stress of the screws. Leakage occurs due to damage and deformation, and the practice of wrapping leak-proof tape around the screw teeth is often prone to damage to the threaded holes.
The fixing screw proposed by Guangdong Yueluo Hardware Industry Co., Ltd. has a screw body 1, and the axial surface of the screw body 1 is formed with extending screw teeth 6, and the axial surface is a column along the central axis direction of the cylinder of the screw body 1. The body surface has a hemispherical screw tail 7 at the bottom, and a screw head 2 at the top. The upper surface of the screw head 2 is provided with a slot (not shown). The screw body 1 is composed of the upper tapered rod 4 and the lower cylindrical screw 5. The tapered rod 4 is an inverted cone, the diameter of its circular upper surface and the diameter of the screw mounting hole 10. equal. The fixing screw also has a washer 3, the washer 3 is arranged between the screw head 2 and the screw body 1, the lower surface of the cylindrical washer 3 has a number of teeth 8, the teeth 8 are along the The upper surface of the inverted cone of the tapered rod 4 and the edge of the washer 3 are connected to form a straight convex strip 15 extending outward; the convex strip 15 can also be designed in an arc shape. The fixing screws for installation proposed by Guangdong Yueluo Hardware Industry Co., Ltd. can be made of metal materials in one piece. As shown in Figure 3, it is a schematic diagram of the installation of Guangdong Yueluo Hardware Industry Co., Ltd. for PCB board fixing. When installing, first pass the screw body 1 of the fixing screw through the mounting hole 10 and the copper column 11 provided on the PCB board 9, so that the tail 7 of the screw reaches the mounting hole 13 on the casing 12, and then use the tightening tool 14 to insert the screw At the notch on the top of the head, forcefully press the inverted cone design taper rod 4 of the screw body 1 into the mounting hole 10, so that the tail 7 passes through the mounting hole 13. Due to the outer diameter D at the bottom of the taper rod and the screw mounting hole The aperture size of 10 is equal, and the fixing screws are pressed and fixed, so that the PCB board 9 can be automatically corrected in the process of fixing its front, back, left and right deflections, and the accuracy of the installation position of the PCB board 9 can be ensured. As shown in Figure 4, after the fixing screw is screwed into the casing, the washer 3 is fully contacted and pressed on the PCB board 9, and the PCB board 9, the copper column 11 and the casing 12 are firmly connected together without sliding. . The teeth 8 on the washer 3 are in full contact with the surface of the PCB board 9, so that a ground wire path is set up between the PCB board 9 and the casing 13 by the metal fixing screw 1, thereby ensuring that the PCB board 9 is fully grounded , the design of the teeth 13 on the washer 3 also has a non-slip function. The fixing screws for installation designed by Guangdong Yueluo Hardware Industry Co., Ltd. make use of the cooperation, friction and electrical conductivity in the mechanical connection, which fully guarantees the firm installation of the PCB board and the chassis and the good grounding of the PCB board. Moreover, the ellipsoid tail of the fixing screw The surface is relatively smooth, even if the mounting holes are exposed, it will not cause scratches on the hands and desktop. The above is only the embodiment of Guangdong Yueluo Hardware Industry Co., Ltd., and does not limit the scope of Guangdong Yueluo Hardware Industry Co., Ltd., any equivalent structure made by using the contents of the description and drawings of Guangdong Yueluo Hardware Industry Co., Ltd. or etc. Effective process transformation, or direct or indirect application in other related technical fields, are also included in the protection scope of Guangdong Yueluo Hardware Industry Co., Ltd.
rivet is a nail-shaped object with a cap on one end: in riveting, the riveted parts are connected by their own deformation or interference. There are many types of rivets, and they are informal. Commonly used are semi-circular head, flat head, semi-hollow rivet, solid rivet, countersunk head rivet, blind rivet, hollow rivet, which usually use their own deformation to connect the riveted parts. Generally, cold riveting is used for those smaller than 8 mm, and hot riveting is used for larger ones. But there are exceptions, such as the nameplate on the three-ring lock, which is riveted by the interference between the rivet and the lock body hole. In addition, there are paired rivets, which are special. Divided into two parts, the thicker section of the rod with a cap has a hole in the center, and the other section of the rod with a cap is an interference fit. When riveting, drive the thin rod into the thick rod. Most of the existing rivets are connected by overall deformation to achieve mutual cooperation. In the ultra-fine-pitch display screen, the rivets used to fix the ultra-fine-pitch display screen have a slender diameter. If they are fixed by overall deformation, they are prone to bending and breaking. and other phenomena, the tightening effect is not good or there is no tightening effect, which damages the components, increases the cost, and wastes time and resources.
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