What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
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.
Pedicle screws can be divided into four types: one-way short-tail screw, one-way long-tail screw, universal short-tail screw and universal long-tail screw. Pedicle screws can effectively complete the three-column fixation of the spine and are clinical The most widely used internal fixation method for the treatment of spine-related diseases. Due to the different types of pedicle screws, four different screwdrivers are required to complete the screw insertion. However, the implantation of pedicle screws is performed in a complex three-dimensional space, which has high difficulty and risk. Mis-implantation of screws may cause instability of the internal fixation frame in the early stage, and may cause false joint formation in the later stage. Therefore, in the process of spinal internal fixation, it is necessary to ensure the accurate implantation of pedicle screws is the key to the success of the entire spinal internal fixation, and the selected implanted instruments are particularly important.
The shaft and gear of financial self-service equipment are often connected by elastic straight groove cylindrical pins. When repairing, the traditional disassembly method is to use the shaft and gear as components. After disassembling together, align the punch with the elastic pin by hand, and use a hammer to remove the elastic pin. Pin out. With this disassembly method, the human hand is easily injured, and the disassembly efficiency is low.
As one of the screws, self-tapping screws can directly drill holes on the plate to be fixed by themselves and lock them together with the plate to be fixed. They are easy to use and have a good fixing effect, so they are widely used. However, in the prior art, when the screw is perforated on the plate to be fixed, it is prone to skew, which affects the fixing effect and also reduces the aesthetics. To sum up, how to overcome the above-mentioned defects of the screw fixing method in the prior art is a technical problem to be solved urgently by those skilled in the art.
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