What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Friction type high-strength bolts: suitable for beam and column connections of steel frame structures, solid web beam connections, heavy-duty crane beam connections in industrial plants, braking systems and important structures bearing dynamic loads. Pressure-bearing high-strength bolts: Can be used for shear connections in statically loaded structures that allow a small amount of sliding or in members that are indirectly loaded with dynamic loads. Tensile high-strength bolts: When the bolts are in tension, the fatigue strength is low. Under the action of dynamic load, its bearing capacity is not easy to exceed 0.6P (P is the allowable axial force of the bolt). Therefore, it is only suitable for use under static load. Such as flange butt joints, T-joints, etc. of pressure members.
The technical solution adopted by Guangdong Yueluo Hardware Industry Co., Ltd. to solve its technical problems is: a waterproof rivet, including an integrally formed waterproof cap and a rivet rod for waterproofing, and the waterproof cap includes a lower part that is fixedly connected with the rivet rod. An end face, the lower end face includes a fixing portion arranged in order from the center position of the lower end face to the outside, a buffer portion arranged circumferentially with the fixing portion as the center, and a waterproof portion arranged circumferentially with the fixing portion as the center, the fixing portion and the rivet The rods are fixedly connected, and the section of the waterproof part is a figure-eight shape.
As one of the screws, self-tapping screws can directly drill holes on the plate to be fixed by themselves and lock them together with the plate to be fixed. They are easy to use and have a good fixing effect, so they are widely used. However, in the prior art, when the screw is perforated on the plate to be fixed, it is prone to skew, which affects the fixing effect and also reduces the aesthetics. To sum up, how to overcome the above-mentioned defects of the screw fixing method in the prior art is a technical problem to be solved urgently by those skilled in the art.
The drawing process has two purposes, one is to modify the size of the raw materials; the other is to obtain basic mechanical properties of the fasteners through deformation and strengthening. For medium carbon steel, medium carbon alloy steel also has another purpose, that is, to make the wire rod. The flaky cementite obtained after controlled cooling is cracked as much as possible during the drawing process to prepare for the subsequent spheroidization (softening) annealing to obtain granular cementite. However, some manufacturers arbitrarily reduce the drawing in order to reduce costs. The excessive reduction rate increases the work hardening tendency of the wire rod, which directly affects the cold heading performance of the wire rod. If the distribution of the reduction ratio of each pass is not appropriate, it will also cause torsional cracks in the wire rod during the drawing process. In addition, if the lubrication is not good during the drawing process, it can also cause regular transverse cracks in the cold drawn wire rod. The tangential direction of the wire rod and the wire drawing die is not concentric at the same time when the wire rod is rolled out of the die, which will cause the wear of the unilateral hole pattern of the wire drawing die to aggravate, make the inner hole out of round, and cause uneven drawing deformation in the circumferential direction of the wire. The roundness of the steel wire is out of tolerance, and the cross-sectional stress of the steel wire is not uniform during the cold heading process, which affects the cold heading pass rate. During the drawing process of the wire rod, the excessive surface reduction ratio will deteriorate the surface quality of the steel wire, while the too low surface reduction ratio is not conducive to the crushing of the flaky cementite, and it is difficult to obtain as much granular cementite as possible. , that is, the spheroidization rate of cementite is low, which is extremely unfavorable to the cold heading performance of the steel wire. For the bar and wire rod produced by the drawing method, the partial surface reduction rate is directly controlled within the range of 10%-15%.
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