What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
However, Yueluo still feels that there should be room for improvement for the screw improvement and screw that integrates stability, labor, fast and multi-function in the above two cases; for example, No. 556784 screw improvement Although the rod has the function of cutting and collecting chips, when the screw starts to screw into the object such as wood, it is hindered by the hardness of the object's tissue, so the staff still needs to exert considerable force, resulting in the lock. In the solid operation, there is still a lack of difficulty in screw-in operation; another example, new cases such as No. 289417 screw that integrates locking, stability, labor-saving, fast and multi-function, although the rod has the structural function of cutting and chip removal, it is The rod part is screwed into the middle section to the rear section of the object. Since the debris cannot be discharged, the rod part pushes the outer part of the object to the surrounding tissue of the object, so that the object expands outwards and even seriously damages the appearance of the object.
The history of screws was broadcast in 1986. Our country formulated a new standard for standard parts, which is commonly known as the new standard in the business. The most used ones are GB5780, GB5781, GB5782, GB5783, GB5784. GB5780 is a hexagonal head thick shank half-thread screw, its accuracy grade is C-grade product, which can be replaced by GB5782 (GB5782 is a hexagonal head thick shank full-thread screw, and its accuracy grade is grade A and B.) GB5781 is a hexagonal head full-thread screw. Threaded screw, the accuracy grade is C grade product. It can be replaced by GB5783 (GB5783 is a hexagonal head full-tooth screw, and its accuracy grades are A and B). GB5784 is a hexagon screw with thin rod and half teeth.
Cylindrical pins are generally used to connect, lock parts or for assembly positioning, and can also be used as parts of safety devices. The cylindrical pin is fixed in the pin hole by interference fit with the pin hole to fix parts, transmit power, or act as a positioning member. The prior art cylindrical pin press-fitting is shown in Figure 1. This kind of cylindrical pin prevents the cylindrical pin body from withdrawing through the locking force and axial friction force brought by the interference fit between the cylindrical pin body and the pin hole. However, the interference of the cylindrical pin body will gradually decrease during use, so that the firmness of the connection and the positioning accuracy will gradually decrease. Therefore, the cylindrical pin can be easily withdrawn during use, resulting in potential safety hazards.
In steelmaking plants, the wheels of metallurgical casting crane trolleys used for hanging liquid metal are connected with cardan shafts through flanges. Usually, a keyway is set in the radial direction of the connecting flange, and the keyway is a through groove. The B-type flat key is set in the keyway to transmit torque. During the frequent forward and reverse motion of the wheel, the flange connection bolts are easily loosened. Since the keyway is a through groove, the B-type flat key is easily caused when the flange connection bolts are loosened. It falls off from the keyway of the connecting flange and cannot transmit the torque, which seriously affects the working efficiency of the locomotive. In addition, because the B-type flat key falls off and cannot transmit the torque, the locomotive can only rely on the connecting bolt to transmit the torque when it continues to work. Poor, it is easy to damage and scrap the connecting bolts, and then damage the connecting flanges, requiring frequent replacement and maintenance, high cost, and difficult maintenance.
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