What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
With the improvement of living standards, people's requirements for the comfort of sitting and bedding are gradually increasing. Independent pocket spring cushions have moderate hardness and are generally welcomed by people.
The screw rod in the ordinary T-slot nut is cuboid, so the T-slot nut can only be inserted into the nut from the end face of the T-slot, which makes it impossible to quickly complete the installation of the T-nut, which is inconvenient to use. Usefulness is greatly limited.
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.
The common types of wood screws are iron and copper, and the types are divided into round head type and other samples of wood screws according to different nail heads. There are two types of slotted screws and cross recessed screws. Generally, the round head screws are made of mild steel and are blue, and the flat head screws are polished. The oval head screws are usually plated with cadmium and chrome, and are often used to install hinges, hooks and other hardware accessories. Specifications are determined by rod diameter, length and nail head type. [1]
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
