What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
1. Precautions for the quality of high-strength bolts or screws and flat washers assemblies. The surface of the Phillips hexagon combination screw should be checked for burrs or scratches. There is no oil stains, or rust. To test the material of the combination screw, the strength of the grade used in different high strengths should be consistent with it. Second, the combination bolt and nut should be used together with the same grade as the nut, and the same grade should be used together. Third, when installing and using combined bolts, it should be in reasonable weather conditions and should not be operated in the rain. Fourth, when installing, it is forbidden to use excessive force and excessive force. Lead to sliding teeth, or locking phenomenon.
Fasteners such as bolts and rivets are called the rice of industry, and they are used in infrastructure construction, equipment machinery, automobile manufacturing, electronic information, aerospace and other industries. According to the mechanical properties of fasteners, fasteners are divided into high-strength fasteners and ordinary fasteners. At the end of the 20th century and the beginning of the 21st century, with the rapid development of the economy, the demand for anti-seismic and anti-loose fasteners surged. Although the fasteners are small, their quality and reliability play an important role in the performance and structural safety of the main engine. Incredible.
When using screws, if you can understand the mechanical properties of screws first, then you can use screws better. Different types of screws have different mechanical properties, and the different mechanical properties lead to different occasions when screws are used. 1. Self-tapping screws: mechanical performance requirements 1. Heart hardness: standard value HRC28-38. When testing, take the section 1-2 times the diameter of the name from the tail. If the length of the name is too short, it can be embedded first, and then the hardness is measured. 2. Surface hardness: standard MIN HV450. 3. Carburized layer: standard 4#-6#: 0.05-0.18mm, 8#-12#: 0.10-0.23 mm, 14#: 0.13-0.28 mm. The main purpose of carburizing is to enhance the surface hardness and ensure the strength of the teeth. If the decarburization is too deep and the carburization is insufficient, the strength of the teeth will not meet the requirements, that is, the teeth will be damaged during the screw-in test. 4. Torque: standard specification 4#5#6#7#8#10#12#14#A tooth 14212835455696145AB tooth 142128354565102165. 5. Screw-in test: screw the self-tapping screw into a steel plate with a reserved test hole. The self-tapping screw should form a matching thread in the test plate, and the thread of the screw itself will not be deformed or damaged until the end. Tapered threads pass completely through the test plate. The screw-in test is only applicable to AB, B, BP and other types of self-tapping screws. It is stipulated in IFI that the test plate shall be prepared from semi-hard low-carbon cold-rolled steel, and the hardness of the steel plate is 70–85HRB in Rockwell. The standard specification of the steel plate, that is, the thickness, is shown in the table below. The test hole should be punched or drilled, and the tolerance is the specified nominal diameter (see the table below) ± 0.025mm. Specifications 6#7#8#10#12#1/4 Test plate thickness (mm) 1.85-1.953.12-3.234.68-4.84 Aperture (mm) ±0.0252.953.263.454.044.765.50.
The main purpose of the screw is to make the industrial product form a fixed one. In use, it often happens that the teeth cannot be closely attached, the screw head will be broken if the screw is locked too hard, or the tooth pattern is not properly locked, etc., and the use conditions are not met, all of which are quality. the problem of accuracy. Screws are mass products, not handmade works of art. In mass production, the purpose is to achieve high-precision and stable quality and popular prices to supply consumers. The accuracy of screws is usually 6g, and the rough screws used in construction projects are 10g. The value of screws is very important. In the world, there are examples of automobile factories going bankrupt because of poor screw quality; there are also examples of planes falling and vehicles being overturned because of poor screw quality.
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