What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Guangdong Yueluo Hardware Industry Co., Ltd. discloses a low-carbon steel rivet nut fastened to a thin-walled and thin-plate fastener. The rivet nut fastener is composed of a brim, a deformed skirt, and a threaded hole. Using low carbon steel cold extrusion, the brim is formed by cold heading, the deformed skirt is extruded in the concave die, and the thread hole of the nut tapping skirt is extruded at the lower end of the deformed skirt. It is characterized in that there are fish teeth under the brim; the outer side of the lower end of the threaded hole has a lead angle; the cross-section of the thread of the inner wall of the threaded hole is an isosceles trapezoid, and the upper bottom of the trapezoid is a concave solitary shape, and the fastener does not need to be welded. , Single-sided riveting, easy operation and firm connection.
The traditional fixture shown in Figure 2 is composed of a hardened support cylinder and a hardened shear bar, and has a simple structure. The cylindrical pin is loaded into the hardened support cylinder, and the shear test is completed by applying an axial load to the hardened shear bar. Since the standard stipulates that the gap between the loading part and the supporting part does not exceed 0.15mm, in order to ensure the matching of the gap during the shear test of the cylindrical pin, the diameter of the cylindrical pin on the cylinder is generally equal to the theoretical cylindrical pin. In practical application, the cylindrical pin is irregular in size after heat treatment. To realize the shear test, the cylindrical pin must be inserted into the hole with the help of external force, which is difficult to install and clamp and takes a long time. If the double-sided shearing is performed, that is If the cylindrical pins need to be installed on both sides, the time is doubled, and the notch of the cylindrical pins cannot be guaranteed to face upwards.
With the rapid development of China's machinery industry, especially the development of heavy industry, the demand for large-scale metal processing equipment is increasing; at the same time, higher requirements are also placed on the technical parameters of the equipment. For some large-scale CNC equipment, to ensure the machining accuracy of the whole product, it is not only necessary to rely on high-performance components such as full closed-loop control and precision transmission components, but also requires the positioning and stability of the joint surfaces between the large and medium-sized components of the equipment. The common positioning of the joint surface between large components adopts flat key positioning, and this method requires processing the keyway at the joint surface of the large components. Since the joint surface of large parts is affected by factors such as processing and splicing, it cannot guarantee that the keyways on the large parts combined can be matched according to the theoretical requirements. Therefore, the positioning flat key needs to press the flat key in the two parts of large parts. Different repair allowances Trim into a stepped shape. The height difference of this keyway in different large components makes a single flat key need to be repaired on four sides, which increases the difficulty of the key repair process and makes it difficult to improve work efficiency. Not only that, when the flat key is repaired and assembled, it must be in an interference fit with the keyway, which makes the disassembly and assembly of the flat key more laborious.
Cylindrical pins are widely used for positioning or connecting components on mechanical equipment, and the cylindrical pins are fixed in the pin holes by means of interference fit. Cylindrical pins are generally processed by a grinding machine and a punch former, but the above processing methods have complex operation procedures, high processing equipment and high processing costs.
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