What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In the design of modern aviation and aerospace vehicles, in order to reduce weight and save space, the space of the fastening installation system is getting narrower and narrower, and blind hole installation is often required. In this case, single-sided riveting installation is usually used for fastening connection. At present, this kind of fastening connection products are mainly blind rivets. The riveting installation principle of blind rivets is to use the method of pulling, pulling the mandrel, and extruding the nail sleeve to deform it at the blind end to achieve the function of fastened connection. This kind of fastening connection method requires special riveting, generally imported riveting, the replacement of internal parts is expensive, the installation process is complicated, and the installation cost is high.
Rivets are nail-shaped objects with a cap on one end: in riveting, the riveted parts are connected by their own deformation or interference. There are many types of rivets, and they are not restricted in form. Commonly used are R-type rivets, fan rivets, blind rivets, tree-shaped rivets Rivets, semi-circular head, flat head, semi-hollow rivets, solid rivets, countersunk head rivets, blind rivets, hollow rivets, these usually use their own deformation to connect the riveted parts, generally less than 8 mm with cold rivets, larger than this size with Hot riveting, but there are exceptions. For example, the nameplate on some locks is riveted by the interference between the rivet and the lock body hole. The rivet pliers are used to cut rivets. The existing rivet pliers have a simple structure and cannot be riveted according to the The user needs to cut a certain length of rivets, and cutting the rivets is time-consuming and labor-intensive, and it is not convenient for people to use.
In addition, the angle aluminum connection structure itself has structural defects of poor torsional and shear resistance, and many projects use larger insulating glass to meet the requirements of architects, resulting in a larger self-weight. In the event of a natural disaster such as an earthquake that will cause the curtain wall to shake violently, the bolts on the angle aluminum are prone to breakage, and the seismic performance is not good. Especially for the beam with the open structure, since the angle aluminum is installed in the opening cavity of the beam, the inertia moment of the beam is small, and the torsion resistance and shear resistance performance of the force are worse.
Materials and main equipment: 1.1 Bolts, nuts and washers shall be accompanied by quality certificates and shall comply with design requirements and national standards. 1.2 The high-strength bolts should be stored in categories according to their specifications, and should be protected from rain and moisture. Do not use if the bolts and nuts are not matched and the threads are damaged. If the bolts, nuts and washers are corroded, the tightening axial force should be sampled and used only after meeting the requirements. Bolts, etc. shall not be contaminated by soil or oil, and shall be kept clean and dry. It must be used in the same batch according to the batch number, and must not be mixed or mixed. 1.3 Main tools: electric torque wrench and controller, manual torque wrench, manual wrench, wire brush, tool bag, etc. 2 Operating conditions: 2.1 Friction surface treatment: The friction surface is treated by sandblasting, grinding wheel grinding and other methods, and the friction coefficient should meet the design requirements (a requirement is that the Q235 steel is above 0.45, and the 16 manganese steel is above 0.55). The friction surface wood is allowed to have residual iron oxide scale. The treated friction surface can generate red rust surface and then install the bolts (generally stored in the open air for about 10d). The sandblasted friction surface can be installed without rusting. When grinding with a grinding wheel, the grinding range is not less than 4 times the diameter of the bolt, the grinding direction is perpendicular to the direction of force, and the friction surface after grinding should be free of obvious unevenness. The friction surface should be prevented from being polluted by oil or paint. If polluted, it should be cleaned thoroughly. 2.2 Check the hole size of the bolt hole, the burrs on the edge of the hole must be removed. 2.3 The bolts, nuts and washers of the same batch number and specification should be packaged for use. 2.4 Electric wrenches and manual wrenches should be calibrated.
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