What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Yueluo relates to a self-tapping screw according to the preamble of claim 1. A self-tapping screw is known from EP0623759B1, the ratio of the outer diameter to the smaller diameter of the self-tapping screw is about 1.25-1.5, the ratio of the outer diameter to the pitch lead is about 1.5-1.6 and the thread The flank angles of , are < 50° and ≥ 35°. EP0433484B1 proposes a self-tapping screw whose thread is provided with cutting teeth of approximately arcuate design, and the cutting edge and the thread crest are at the same horizontal position and are set in opposite directions. One purpose of Yueluo is to realize a general type of self-tapping screw so that it can be screwed particularly easily into holes drilled in concrete or other materials such as bricks and the like. According to Yueluo, this object is achieved by the features in the characterizing part of claim 1, and surprisingly, it has been found that the parallel arrangement of the flanks, ie with a flank angle of about 0°, will make screwing particularly easy when screwing in , especially if the diameter of the hole varies within an allowable tolerance. One reason may be due to the fact that there is no lateral pressure on the material screwed into the thread, even if threads of different depths are cut in concrete or other materials such as brick, chipped plywood, or hardwood. The thread cuts into the material over its entire width by cutting grooves. In particular according to the embodiment of claim 3 the material cut out when screwing in the screw can be discharged without any accumulation, the dependent claims reflecting many advantages of further embodiments.
For a long time, the rivets used in general riveting, especially the ordinary rivets and bolts and other fasteners commonly used in steel structures such as vehicles and bridges, have low connection reliability, especially under alternating load and impact conditions. Looseness is easy to occur, the maintenance cycle is short, and the maintenance cost is high in the later period, which cannot meet the requirements of railway freight.
Most of the existing screws use an integral metal structure, and there are still some problems, such as large weight, high cost of materials, wear resistance, hardness, rust resistance, corrosion resistance, high and low temperature resistance, brittleness, toughness, etc. Many occasions cannot meet the needs of production, and further improvements are needed to improve production efficiency, reduce costs, improve safety, and prolong the service life of screws.
At present, the convex washers with traditional structures on the market have unreasonable designs and complex structures, and are inconvenient to install and disassemble. After long-term use, they are prone to fracture and deformation due to poor toughness, resulting in short service life and requiring regular downtime for maintenance, affecting assembly. The working efficiency and safety of its equipment are also poor in terms of wear resistance, corrosion resistance, and high temperature resistance. Regular replacement and maintenance also increase the economic cost of production. Therefore, the convex gasket of the existing structure can no longer meet the existing mechanical requirements. The high standard use requirements of assembly auxiliary parts are urgently needed to be solved at present.
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