What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Specification label broadcast representation format: Thread specification d=M12, nominal length L=80mm, and performance level 4.8 equal-length stud bolts are completely marked as: GB 901 M12×80 [1] Product example: Stud studs are generally required After surface treatment, there are many types of bolt surface treatment, commonly used are electroplating, blackening, oxidation, phosphating, electroless zinc flake coating treatment, etc. However, electroplated fasteners account for a large proportion of the actual use of fasteners. Especially in automobiles, tractors, home appliances, instrumentation, aerospace, communications and other industries and fields are more widely used. However, for threaded fasteners, not only a certain anti-corrosion capability is required in use, but also the interchangeability of threads must be ensured, which can also be called screwability here. In order to meet the dual-use performance of anti-corrosion and interchangeability required by threaded fasteners in use, it is very necessary to formulate special plating standards.
The shear strength of a metal material refers to the ability of the material to withstand shearing force, which refers to the strength of the external force perpendicular to the material axis and shearing the material. The test is usually to install the cylindrical pin into the specified fixture, and the gap between the supporting part and the loading part is required to be no more than 0.15mm, and then force is applied to test the shear strength of the material.
Hydraulic wrench or pulling method Use hydraulic torque wrench or puller to fasten large screws, which saves effort and has high precision. However, hydraulic tools are expensive, screws of different sizes need to be equipped with different wrenches, and now the hydraulic pullers in the world are generally only M160×6. If the screws are too large, special specifications or very few in number, it is extremely uneconomical to equip them with hydraulic tightening tools.
The existing structure is found in the practical application experience that there are still the following problems and drawbacks: the screw structure and the screw space are combined with each other in a complementary manner, so they can provide a higher torque value, however, not every workpiece. The combination requires a high torque value, so it often results in excess quality. Although the price of the screw is low, if it can change the unchanging structure of the traditional screw, it can provide a technical means to simplify (change) the process. The effect of improving production capacity and convenience of use is indeed a technical bottleneck that the relevant industry should break through.
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