What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The main part of the pin screw is an ordinary screw, and the pin can be arranged in the melting section of the screw or the drop groove of the metering section or the smooth cylindrical surface without screw grooves at the end of the metering section. The pins are arranged in a certain arrangement, with varying degrees of density and quantity. Cylindrical pins are formed by fitting the pins into the holes of the threaded rod; square or diamond-shaped pins are formed by milling directly on the threaded rod. If these pins are set in the melting zone, the pins can break up the solid bed, destroy the two-phase flow, stir the solid and liquid phases together, increase the contact area between the undissolved solid phase fragments and the contained material, and promote molten. If the pin is set in the melt conveying area, its main function is to divide the material flow, increase the interface, change the direction of the material flow, and rearrange the flow beam. Divide and merge multiple times, change the flow direction, and homogenize the melt composition and temperature. The mixing section is an inwardly slotted structure arranged at the end of the common screw homogenizing section, and its outer diameter is equal to the outer diameter of the screw. The grooves are divided into several groups, and each group is the confluence area of the material. The materials are divided by grooves, meet in the confluence area, and then divide and confluence. The principle is similar to the pin type. The characteristic of the separate screw is that in addition to the original screw thread (called the main screw) on the melting section, there is also an additional thread (called an additional thread) whose outer diameter is slightly smaller than the outer diameter of the main thread, and the main and auxiliary threads are With different leads, the secondary thread starts from the end of the feeding section (and connects with the feeding section here), and after several threads, gradually intersects the main thread of the homogenizing section. The screw groove depth and thread lead of this kind of screw change gradually from the beginning of the feeding section to the end of the homogenization, that is, the thread lead gradually narrows from the width, and the groove depth gradually becomes shallower from the depth, which can maximize the compression of the material.
High-strength bolt connection has the advantages of simple construction, good mechanical performance, disassembly and replacement, fatigue resistance, and no loosening under dynamic load. It is a promising connection method. High-strength bolts use a special wrench to tighten the nut, so that the bolt generates a huge and controlled pre-tension. Under the action of pre-pressure, a large frictional force will be generated along the surface of the connected parts. Obviously, as long as the axial force is less than this frictional force, the components will not slip and the connection will not be damaged. This is the high-strength bolt connection. principle. High-strength bolted connections rely on the friction between the contact surfaces of the connectors to prevent them from sliding each other. In order to make the contact surfaces have sufficient friction, it is necessary to increase the clamping force of the components and increase the friction coefficient of the contact surfaces of the components. The clamping force between the components is achieved by applying pretension to the bolts, so the bolts must be made of high-strength steel, which is why it is called high-strength bolted connections. In high-strength bolted connections, the friction coefficient has a great influence on the bearing capacity. Tests show that the coefficient of friction is mainly affected by the form of the contact surface and the material of the components. In order to increase the friction coefficient of the contact surface, methods such as sandblasting and wire brush cleaning are often used to treat the contact surface of the components within the connection range during construction.
In general, the size, mechanical properties and working performance requirements of self-tapping screws have the following standards: 1. Self-tapping screw size standard ASME B18.6.3 2010 standard not only introduces the dimensions of slotted and cross-recessed self-tapping screws and metal drive screws, but also includes the mechanical properties and work performance requirements of carbon steel self-tapping screws. The appendix gives instructions for measuring the various dimensions and application guidance on clamping lengths and test apertures. 2. Self-tapping screw performance standards (including mechanical properties and work performance): (1) SAE J933: Introduces the mechanical performance and work performance requirements of carbon steel ordinary self-tapping screws and white-cut self-tapping screws. The requirements for selection of raw materials, heat treatment, depth of carburized layer, surface hardness, and core hardness are further specified. (2) SAE J81: The mechanical properties and working performance of self-extrusion self-tapping screws (self-tapping locking screws) are introduced. (3) SAE J78: The mechanical properties and working properties of self-drilling and self-tapping screws are introduced. (4) IFl-113: The mechanical properties and working properties of self-drilling and self-tapping screws are introduced. (5) ASTM C1513: Introduces the mechanical properties and performance requirements of carbon steel self-tapping screws. For other special types of self-tapping screws, there is no corresponding national or industrial standard, and no data for self-tapping screws made of other metal materials other than carbon steel have been recognized. For technical data on these self-tapping screws, you can check with the manufacturer.
The assembly of hollow rivets and flat head screws riveted on the cover plate is assembled in the product. Compared with the method of connecting with bolts, the loading and unloading speed can improve the efficiency by about 80% to 90%, and is widely used. The assembly needs to riveted hollow rivets and flat head screws on the cover plate, and ensure that the riveted flat head screws can rotate flexibly. When riveting, it is necessary to use special tools to riveted the hollow rivets, flat head screws and cover plates together for riveting. In the existing riveting process, the oval head screw is often damaged due to the action of external force. The positioning process is cumbersome and the work efficiency is low.
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
