What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Riveting is a method for combining two pieces of metal. Therefore, riveting technology is often used to fasten rivets such as nuts or rivets to metal sheets.
The flat key is simple in manufacture, reliable in operation, convenient in assembly and disassembly, and widely used. The flat key transmits torque by contacting the two sides of the keyway with the two sides, that is, the side is the working surface, so the main technical requirements for assembly are: to ensure the matching requirements between the flat key and the keyway of the parts on the shaft, and to transmit the movement smoothly and torque. The matching nature of the key and the keyway generally depends on the working requirements of the mechanism. The key can be fixed on the shaft or the hub, and can slide relative to another matching part (guide flat key); it can also be fixed on the shaft and the hub at the same time (ordinary flat key), and based on the size of the key, by changing the shaft The size of keyway and hub keyway can meet different matching requirements.
The upper part of the T-bolt is a screw rod, and the bottom end is a T-shaped head. It is equipped with a sleeve with an anchoring plate. The fastening equipment is installed by the anchoring force between the T-shaped head and the anchoring plate. The appearance of the equipment after installation is shown in Figure 1, in which the figure composed of black lines is a component composed of T-bolts and integral sleeves. When constructing civil foundations, the sleeves should be pre-buried first, and the T-bolts will not be used until the equipment is installed. Anchor into the sleeve.
Several concepts about high-strength bolts 1. According to the specified performance level of bolts above 8.8, they are called high-strength bolts. The current national standard only lists M39. For large-size specifications, especially those with a length greater than 10 to 15 times High-strength bolts, domestic production is still short-term. The difference between high-strength bolts and ordinary bolts: High-strength bolts can withstand larger loads than ordinary bolts of the same specification. High-strength outer hexagon bolts High-strength outer hexagon bolts are made of Q235 (ie A3). The material of high-strength bolts is 35# steel or other high-quality materials, which are heat-treated after being made to improve the strength. The difference between the two is the difference in material strength. From raw materials: High-strength bolts are made of high-strength materials. The screws, nuts and washers of high-strength bolts are all made of high-strength steel, such as No. 45 steel, 40 boron steel, 20 manganese titanium boron steel, 35CrMoA, etc. Ordinary bolts are usually made of Q235 (equivalent to A3 in the past) steel. In terms of strength grades: high-strength bolts are increasingly used. Two strength grades are commonly used, 8.8s and 10.9s, of which 10.9 is the majority. The strength level of ordinary bolts is lower, generally 4.4, 4.8, 5.6 and 8.8. High-strength bolts High-strength bolts are viewed from the force characteristics: high-strength bolts apply pretension and transmit external forces by friction. Ordinary bolt connection relies on the shear resistance of the bolt and the bearing of the hole wall to transmit the shear force. When the nut is tightened, the pre-pressure is very small, and its influence can be ignored. In addition to its high material strength, high-strength bolts also exert a large amount of pressure on the bolts. The pre-pressure generates extrusion force between the connecting components, so that there is a large friction force perpendicular to the direction of the screw, and the pre-pressure, anti-slip coefficient and steel type directly affect the bearing capacity of high-strength bolts. According to the force characteristics, it is divided into pressure type and friction type. The calculation methods of the two are different. The minimum specification of high-strength bolts is M12, and M16~M30 are commonly used. The performance of super-large bolts is unstable and should be used with caution in design.
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