What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
After the centrifugal fan blade is assembled in the square cabinet, it needs to be fixed with nuts. The components needed to fix the centrifugal fan blades are gaskets, washers and nuts. During the operation, it is necessary to assemble the gasket, washer and nut in sequence, then drip the fastening glue, and then fix it.
Most electrical appliance manufacturers only require the size and riveting gap to be tested for riveted contact components. There is no clear requirement for riveting strength. Only a few manufacturers perform torsion testing on riveting strength. The torque detection method is as follows: use a saw blade to open a one-shaped groove on the rivet head of the riveted contact element, and then insert a torque wrench into the one-shaped open groove to rotate, and measure the torque value. Because most of the electrical contacts are made of copper-silver alloy, the strength is low, and it is easy to slip during the test, and when a saw blade is used to open the one-shaped groove, the width and depth cannot be accurately positioned, so the measured value fluctuates greatly. , has always been an unsolvable technical problem in the industry.
Although there are many types of self-tapping screws, they all have the following common points: (1) They are generally made of carburized steel (accounting for 99% of the total output). Also available in stainless steel or non-ferrous metals. (2) The product must be heat treated. Carbon steel self-tapping screws must be carburized, and stainless steel self-tapping screws must be solution hardened. In order to make the self-tapping screw meet the mechanical properties and performance required by the standard. (3) The product has high surface hardness and good core toughness. That is, inner softness and outer rigidity. This is a major feature of the performance requirements of self-tapping screws. If the surface hardness is low, it cannot be screwed into the matrix; if the toughness of the core is poor, it will break as soon as it is screwed, and it cannot be used. Therefore, inner soft outer steel is a very important requirement for self-tapping screws to meet the performance requirements. (4) The surface of the product needs surface protection treatment, generally electroplating treatment. The surface of some products must be treated with phosphate (phosphating), such as wallboard self-tapping screws are mostly phosphated. (5) Produced by cold heading process. It is recommended to use high-speed cold heading machine and high-speed thread rolling machine or high-speed planetary thread rolling machine for production. The emphasis here is on high speed to ensure product quality. Only self-tapping screws produced by high-speed machines have well-formed heads and high-quality threads.
The flat washer is mainly used to reduce the pressure. When some parts are tightened with a large axial force, it is easy to press the washer into a dish shape. At this time, it can be solved by changing the material and increasing the hardness.
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