What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Generally known bolts refer to screws with a larger diameter. According to this statement, the diameter of screws is much smaller than that of bolts. Stud bolts do not have a head, and some are called studs. Both ends of the stud are threaded, with no thread in the middle and a smooth rod in the middle. Studs are used on large equipment such as gear racks. In actual use, the external load will have vibration and the influence of temperature will reduce the frictional force, and the threaded connection will loosen and fail over time. Therefore, it is necessary to do a good job in the maintenance of the stud bolts at ordinary times. Stud bolts or anchor bolts will have problems under the action of mechanical friction for a long time. When problems occur, the engine oil pan should be removed, and the use of the engine bearing bushes should be carefully checked, and the clearance between the bearing bushes should be checked. Whether it is too large, if the gap is too large, it should be replaced in time. When replacing the stud bolts, also replace the connecting rod bolts. When some large equipment such as nail making machines are in normal operation, if they find that the engine is not running very stable or there is abnormal noise, they should stop and check in time to avoid bigger problems.
Type 1) Slotted ordinary screws are mostly used for the connection of smaller parts. It has pan head screws, cylinder head screws, countersunk head screws and countersunk head screws. The head strength of pan head screws and cylinder head screws is high, and they are connected to common parts; the head of semi-countersunk head screws is arc-shaped, and its top is slightly exposed after installation, and it is beautiful and smooth. It is generally used for instruments or Precision machinery; countersunk head screws are used where the nail head is not allowed to be exposed. 2) The head of the hexagon socket head cap screw and the hexagon socket head flower screw can be embedded in the component, which can apply a large torque and have a high connection strength, which can replace the hexagonal bolt. It is often used in joints where compact structure and smooth appearance are required. 3) Cross recessed ordinary screws have similar functions to slotted ordinary screws, and can be replaced by each other, but the cross recessed ordinary screws have higher groove strength, are not easy to be bald, and have a more beautiful appearance. When using it, it must be loaded and unloaded with the matching cross-shaped screwdriver. 4) Lifting ring screw Lifting ring screw is a kind of hardware accessories for load-bearing during installation and transportation. When in use, the screw must be screwed in to the position where the supporting surface is tightly fitted, and tools are not allowed to be tightened, nor is a load perpendicular to the plane of the lifting ring allowed to act on it. 5) Set screws Set screws are used to fix the relative position of the parts. Screw the set screw into the screw hole of the part to be fastened, and press its end against the surface of the other part, that is, to fix the former part on the latter part. Set screws are usually made of steel or stainless steel, and their end shapes are conical, concave, flat, cylindrical and stepped. The end of the tapered or concave end set screw directly presses the parts, and is generally used in places that are not often disassembled after installation; the end of the flat end set screw is smooth and does not damage the surface of the parts after tightening, and is used for frequent adjustment of the position. At the connection, only a small load can be transmitted; the cylindrical end fixing screw is used in the fixed position that needs to be adjusted frequently, it can withstand a large load, but the anti-loosening performance is poor, and anti-loosening measures should be taken when fixing; Set screws are suitable for fixing parts with thicker walls. 6) Self-tapping screws When self-tapping screws are used on the connected parts, threads may not be pre-made at the connected parts. Use the screw to tap the thread directly when connecting. It is often used to join thin metal plates. There are two types of taper end tapping screws and flat end tapping screws. 7) Self-tapping locking screw Self-tapping locking screw not only has self-tapping effect, but also has low screw-in torque and high locking performance. Its thread is a triangular section, and the surface of the screw is hardened and has high hardness. Its thread specifications are M2 ~ M12.
Fasteners play a very important role in the installation of the main engine. Complex products such as airplanes, automobiles, trains, elevators, air conditioners, and computers all have the problem of installing components on thin plates. There are two traditional installation processes. One is The first is to tap the internal thread on the thin plate, but when the internal thread is tapped on the thin plate below 6 mm, the installation is often not firm because the number of threads is too small, and even the connection fails due to the broken thread when the force is applied; the second way It is a process of welding nuts on a thin plate, which easily leads to deformation of the thin plate and uneven welding surface. Sometimes the welding is not strong and the nut falls off when the force is applied, resulting in damage to the installation. The development of rivet nuts has solved the problem of installing components on thin plates, because rivet nuts combine the characteristics of nuts and rivets, and play an increasingly important role in fastener products. However, with the extensive use of rivet nuts in the electromechanical and mechanical industries such as automobiles, aviation, railways, refrigeration, elevators, etc., ordinary rivet nuts can no longer meet the special assembly requirements of many mechanical and electromechanical products, such as good sealing during assembly. Rivet nut with leak-proof function. Cantonese snail
The post-treatment of nickel-phosphorus plating includes two main processes of driving hydrogen and polishing. ①Hydrogen drive; according to the relevant standards, the hydrogen drive temperature after plating is 200±10℃, and the treatment time is 2h. 200 ℃ is beneficial to eliminate hydrogen embrittlement, relax internal stress, improve the bonding force between the coating and the substrate, and improve the corrosion resistance of the coating. ②Polishing; the polished bolt has a bright appearance, but in order to better improve the quality of the coating, smooth the tiny traces, and obtain a bright mirror-like surface, the coating needs to be polished with a polishing machine.
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