What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Rivet nuts are mostly used in some chassis cabinets, square tubes and round tubes, fan production, equipment production, and zinc steel guardrails. Next, let’s talk about rivet nuts. The rivet nuts are also used on the top of the chassis cabinet sheet to provide threads. Its mode of operation is to use a riveting machine for riveting. In this case, the requirements will be higher, and a riveting machine is required. After the pressure riveting nut is riveted to the upper side of the sheet, it is very flat and will not have protrusions. Pressure riveting nuts are mainly used in the production of some chassis and cabinets, as well as some equipment production, water pumps, automobiles, and other production enterprises.
Usually, the forming of the bolt head adopts cold heading plastic processing. Compared with the cutting process, the metal fiber (metal wire) is continuous along the shape of the product, and there is no cut in the middle, thus improving the strength of the product, especially the mechanical properties. The cold heading forming process includes cutting and forming, single-station single-click, double-click cold heading and multi-station automatic cold heading. An automatic cold heading machine performs multi-station processes such as stamping, heading forging, extrusion and diameter reduction in several forming dies. The processing characteristics of the original blank used by the single-station or multi-station automatic cold heading machine are determined by the size of the bar with a length of 5-6 meters or the wire rod with a weight of 1900-2000KG, that is, the characteristics of the processing technology. The point is that cold heading does not use pre-cut single blanks, but uses the automatic cold heading machine itself to cut and upset (if necessary) blanks from bars and wire rods. Before extruding the cavity, the blank must be shaped. A blank that meets the technological requirements can be obtained by shaping. Before upsetting, reducing and positive extrusion, the blank does not need to be shaped. After the blank is cut, it is sent to the upsetting and shaping station. This station can improve the quality of the blank, reduce the forming force of the next station by 15-17%, and prolong the life of the die, and the bolts can be made with multiple diameter reductions. The precision that can be achieved by cold heading is also related to the selection of the forming method and the procedure used. In addition, it also depends on the structural characteristics of the equipment used, the process characteristics and its state, the precision of the tool and die, the life and the degree of wear. For high-alloy steel used in cold heading forming and extrusion, the roughness of the working surface of the cemented carbide mold should not be greater than Ra=0.2um. When the roughness of the working surface of this type of mold reaches Ra=0.025-0.050um, it has the highest life.
The inner hole retaining ring groove processing mechanism is characterized in that: it comprises a pneumatic grinder fixed block installed on the tool table of the lathe, a pneumatic grinder installed on the pneumatic grinder fixed block and a grinding wheel piece installed on the front end of the pneumatic grinder; The pneumatic grinder mounting block is provided with a pneumatic grinder installation through hole, and there are at least 2 screw holes above the pneumatic grinder installation through hole; the grinding wheel is designed according to the diameter of the product and the thickness of the groove width, in order to increase the strength of the grinding wheel , Add flanges at both ends of the grinding wheel to improve the strength of the grinding wheel. The grinding wheel piece includes the connecting blade on the flange plate. The center of the flange plate is provided with a mounting hole installed on the pen-type pneumatic grinder. The diameter of the mounting hole is 17.8- 18mm, the diameter of the grinding wheel is 18-20mm.
As one of the indispensable parts in automobiles, the main function of the screw is to fix the parts with through holes and the parts with screw holes together. The existing automobile screws include a screw rod and a head, and the thread pitches on the screw rod are equal. , When in use, directly screw the screw into the screw hole, so as to connect and fix the two parts, this connection method, however, when the screw has different thread spacing or part of the thread is damaged, the thread cannot be repaired and replaced. Then the whole screw will be scrapped.
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