What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
GB 3098.1 Mechanical Properties of Fasteners Bolts, Screws, Studs and Nuts GB 3098.6 Mechanical Properties of Fasteners Stainless Steel Bolts, Screws, Studs and Nuts GB 3103.1 Tolerances of Fasteners Bolts, Screws and Nuts GB 5267 Electroplating of Threaded Fasteners GB 5779.1 Surface Defects of Fasteners - Bolts, Screws and Studs - General Requirements GB 5779.3 Surface Defects of Fasteners - Bolts, Screws and Studs - Special Requirements
In the switchgear of high and low voltage power equipment, the surface of many switchgear shells is painted or sprayed with plastic, and the installation beams and other parts of the switchgear and the entire cabinet must be continuously grounded according to the requirements of switchgear standards to improve the safe use of equipment. Because the common screw, spring washer, flat washer and nut type structural connection between the surface of the shell and the metal mounting beam cannot meet the requirements of grounding continuity, in order to meet the requirements, the surface of the shell is painted or Before spraying, special grounding studs must be welded. With the increase of installation beams, the number of welded studs must also increase, which increases the complexity of the product processing technology, wastes man-hours and increases costs.
It can be seen from the extrusion process that the screw works under high temperature, certain corrosion, strong wear and high torque. Therefore, the screw must: 1) High temperature resistance, no deformation under high temperature; 2) Wear resistance, long life; 3 ) Corrosion resistance, the material is corrosive; 4) High strength, can withstand large torque, high speed; 5) Good cutting performance; 6) After heat treatment, the residual stress is small, and the thermal deformation is small. [1]
Screws and bolts are common connecting fasteners. The diameter of the thread is as small as less than one millimeter and as large as several hundred millimeters or even larger. The vast majority of threaded connections are pre-tightened during assembly in order to enhance the rigidity, tightness, anti-loosening ability of the connection and prevent the sliding of the bolted connection under lateral load. The pre-tightening force is determined according to the force of the bolt group and the working requirements of the connection. For important threaded connections, the preload must be measured and controlled.
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