What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The nuts of some products must be installed on the outside, but due to the small internal space, when the indenter of the riveting machine cannot meet the strength requirements by methods such as riveting and budding, riveting and riveting are impossible. Rivets to be nailed. Applicable to the fixed field of each thickness plate and tube (0.5MM-6MM). Using pneumatic or manual riveting equipment, rivet once and it is easy to secure. Replacement of the existing welding nut to supplement the metal plate, the thin tube welding is easy to melt, and the welding nut is not smooth.
Sometimes, the iron screws are often seen broken, and sometimes, the stainless steel screws are also seen broken. But generally speaking, stainless steel screws rarely break. Because the stainless steel screw wire itself is relatively hard. But under certain circumstances, stainless steel screws can still break. So what are the main reasons for stainless steel screws to break? The reasons for the fracture of stainless steel screws are as follows: 1. The quality of raw materials used for stainless steel screws is poor, and the quality of stainless steel screws is not good. There are many impurities, impure, resulting in insufficient hardness of stainless steel screws. 2. The production process of stainless steel screws. For example, stainless steel screws with eccentric head and eccentricity, and the Q value is too deep and the R position design is too small during the down punching operation during production. 3. The customer uses too much force when using stainless steel screws. Generally, you do a torque test to see how much the minimum breaking force is, and then adjust the torque. Of course, stainless steel screws must be broken for more than three reasons. But the above three reasons are the main reasons for the fracture of stainless steel screws. When the stainless steel screw is found to be broken, it can be checked step by step. Find out what's causing it.
The inner tooth elastic washer and the outer tooth elastic washer have many sharp elastic warping teeth on the circumference, which are pressed against the supporting surface and can prevent the loosening of the fastener. The inner tooth elastic washer is used under the screw head with smaller head size; the outer tooth elastic washer is mostly used under the bolt head and the nut. The elastic washer with teeth is smaller than the ordinary spring washer, and the fastener is evenly stressed and reliable to prevent loosening, but it is not suitable for frequent disassembly. Wave spring washer GB: GB/T 7246-1987 Wave washer is divided into WG type, WL type, WN type WG type wave washer WG type wave washer is an open elastic washer, which can usually be installed in a small space, such as giving The bearing is prestressed to reduce the noise of the bearing operation and improve the running accuracy and stability of the bearing. In addition, there are a large number of applied materials in electronic appliances, such as carbon steel, stainless steel, copper alloy and so on. WL-type wave washer WL-type wave washer is a lap-type elastic washer, which can usually be installed in a small space, such as prestressing the bearing, reducing the noise of the bearing operation, and improving the running accuracy and stability of the bearing. There are also a large number of applications in electronic appliances. Materials are carbon steel, stainless steel, copper alloy, etc. WN type wave washer WN type wave washer is a multi-layer wave crest overlapping elastic washer. Compared with the WL type, this series is composed of multi-layer materials, so the K value curve under the same compression stroke is flatter than that of the WL type, which is suitable for elastic force. Larger, and the elastic release of the entire working stroke is required to be more uniform. The materials used are carbon steel, stainless steel, copper alloy, etc. Disc spring washer Disc spring washer, also known as Belleville spring washer, was invented by the French Belleville. DIN6796 Disc Spring Washers (HDS Series) are lock washers designed for bolted and screwed connections. It is designed and manufactured according to DIN 6796 for the connection of medium or high strength bolts and screws. High bearing loads and elastic recovery make the HDS series very effective, and the bolt tension can withstand slack due to: wear of consumables, creep, relaxation, thermal expansion, contraction, or compression of seals. The HDS series increases the elasticity of the screw several times. It can effectively replace the ordinary spring washer, but it is not suitable for the combination of lock washer and flat washer. Since the HDS series is a disc spring that can be folded or overlapped. The combination of the butt joint can increase the deformation of the disc spring group, and the combination of the overlapping method can increase the spring force of the disc spring group. The ideal installation method is to flatten as much as possible. The closer it is to the flattened state, the faster the tension torque increases, and the proper bolt tension can be obtained without a torque wrench.
In the manufacture of fasteners, the correct selection of fastener materials is an important part, because the performance of fasteners is closely related to its materials. If the material is improperly or incorrectly selected, the performance may not meet the requirements, the service life may be shortened, or even accidents or processing difficulties may occur, and the manufacturing cost will be high. Therefore, the selection of fastener materials is a very important link. Cold heading steel is a steel for fasteners with high interchangeability produced by cold heading forming process. Because it is formed by metal plastic processing at room temperature, each part has a large amount of deformation and a high deformation speed. Therefore, the performance requirements of cold heading steel raw materials are very strict. On the basis of long-term production practice and user research, combined with GB/T6478-2001 Technical Conditions for Cold Heading and Cold Extrusion Steel GB/T699-1999 High-Quality Carbon Structural Steel and target JISG3507-1991 Cold Heading Characteristics of Carbon Steel Wire Rod for Steel, taking the material requirements of grade 8.8 and grade 9.8 bolts and screws as an example, the determination of various chemical elements. If the C content is too high, the cold formability will be reduced; if it is too low, the mechanical properties of the parts cannot be met, so it is set at 0.25% - 0.55%. Mn can improve the permeability of steel, but adding too much will strengthen the matrix structure and affect the cold forming performance; when the part is quenched and tempered, it has the tendency to promote the growth of austenite grains, so it should be appropriately improved on the basis of international standards. 0.45 % - 0.80 %. Si can strengthen the ferrite and reduce the cold formability. SP is an impurity element, and their existence will cause segregation along the grain boundary, resulting in the embrittlement of the grain boundary and damage to the mechanical properties of the steel. It should be reduced as much as possible. B. The maximum value of boron content is 0.005%, because although boron element can significantly improve the permeability of steel, it will also increase the brittleness of steel. Excessive boron content is very unfavorable for workpieces such as bolts, screws and studs that require good comprehensive mechanical properties.
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