What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
1. For low strength (below 500 N/mm2 or below 60000 psi) bolts use general soft steel, generally use SAE 1008 or JIS SWRM 8 (or SWRCH 8). 2. Lower strength (600 N/mm2 or 74000 psi) ) bolts use general soft steel, but limited carbon content grade, generally use SAE 1010 - 1015 or JIS SWRM 10 - 15 (or SWRCH 10 - 15). .3. Higher strength ( 800 N/mm2 or 125000 psi ) bolts of medium carbon steel, low carbon boron steel plus quenching and tempering, generally use SAE 1035 - 1040 or SWRCH 35K - 40K. 4. High strength (900 N/mm2 or more or 150000 psi or more) bolts use medium carbon Alloy steel or low carbon boron steel, in terms of application, if the metric Class 10.9 uses low carbon boron steel, the imprint should be added under the series imprint to become 10.9, and the imprint of the inch 8.2 grade is also used with the general Grade 8 bolts The imprint is different for easy identification. High-strength bolts made of low carbon boron steel cannot be used in high temperature conditions. The design strength exceeds Class 12.9 or ASTM A574 ultra-high strength bolts are limited to medium carbon alloy steel plus quenching and tempering. The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenching, tempering), commonly known as high-strength bolts, the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value and yield ratio of the bolt material respectively. For example, a bolt with a performance level of 4.6 means: 1. The nominal tensile strength of the bolt material is 400MPa; 2. The yield ratio of the bolt material is 0.6; 3. The nominal yield strength of the bolt material is 400×0.6=240Mpa . Performance level 10.9 high-strength bolts, after heat treatment, can achieve: 1. The nominal tensile strength of the bolt material is 1000MPa; 2. The yield ratio of the bolt material is 0.9; High-strength bolts, processing and manufacturing problems are compared Small, general fastener manufacturing companies can master the manufacturing process; but problems are prone to occur in material selection and heat treatment. Material selection is the primary link. Various alloying elements have a great influence on the properties of the material, and the material must be subjected to spectral composition analysis; secondly, the fracture problem and the choice of heat treatment process have a great influence and are very important. Dealers and traders must control the inspection and performance testing links; automotive fasteners have high requirements and must carefully control the quality.
The paint mixing mixer used for color matching in the auto repair industry uses a multi-link connection transmission as the main driving force. The transmission of torque has higher quality requirements for the impact resistance and fatigue resistance of the cotter pin. During the use of the cotter pin, it was found that the cracking phenomenon occurred due to insufficient strength, resulting in the machine not running. In the existing multi-link transmission mode of the paint mixing mixer, the connecting rod drives more than 10 paint pots in each layer of the frame to stir, and the bottom connecting rod is also responsible for the transmission of the torque of the upper connecting rod, which leads to the connection between the connecting rod and the connecting rod. The pins connected by the rods must have strong impact resistance and fatigue resistance, and must have a certain anti-loosening function.
The manual dismantling of the rivets of the automobile frame delays the production cycle of the product and increases various production costs, so a special tooling is desperately needed to meet the actual needs.
The existing nut fasteners are generally used to fix the bolts to fix the devices with holes. However, during the operation of most devices, the bolts and nuts are easily loosened and separated due to mechanical vibration, causing long-term vibration. It will cause the nut to separate from the bolt, affecting the safety and stability of the device during operation. At the same time, in the connection between the bolt and the nut for a long time, the external dust easily enters the connection, resulting in the accumulation of dust, making the bolt and nut difficult to disassemble. Affect the use of fasteners.
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