Service HotlineThread Code Broadcast Coarse Thread Series UNC Fine Thread Series UNF Extra Fine Thread Series UNEF Fixed Pitch Series UN Marking Method Broadcast Marking Method: Thread Diameter - Number of Threads per Inch Serial Code - Accuracy Grade Example: Coarse Thread Series 3/8—16 UNC— 2A Fine pitch series 3/8—24 UNF—2A Extra fine pitch series 3/8—32 UNEF—2A Fixed pitch series 3/8—20 UN—2A The first digit 3/8 indicates the outer diameter of the thread, in inches , to convert to metric unit mm, multiply by 25.4, that is, 3/8×25.4=9.525mm; the second and third digits 16, 24, 32, 20 are the number of teeth per inch (the number of teeth on the 25.4mm length); The text code UNC, UNF, UNEF, UN after the third digit is the series code, and the last two digits 2A are the precision grade. UNC: Unified Coarse Thread.
At present, there are two commonly used nut fixing methods, one is welding fixing: high energy consumption, the welding process easily leads to thread deformation in the nut, which requires re-tapping, which increases the cost, and for aluminum alloy and other materials, the welding process is poor, It is easy to produce welding defects and cannot achieve the function of fastened connection; the other is to pull riveting: in this method, the connection force of the nut is not strong, the reliability is not good, and it is not suitable for thin-walled profiles.
Stainless steel bolts refer to bolts made of stainless steel, including stainless steel SUS201 bolts, stainless steel SUS304 bolts, stainless steel SUS316 bolts, and stainless steel SUS316L bolts. The performance grades of stainless steel bolts, studs and studs are divided into 10 grades: from 3.6 to 12.9. The number before the decimal point represents 1/100 of the tensile strength limit of the material, and the number after the decimal point represents 10 times the ratio of the yield limit to the tensile strength limit of the material.
Type 1) Slotted ordinary screws are mostly used for the connection of smaller parts. It has pan head screws, cylinder head screws, countersunk head screws and countersunk head screws. The head strength of pan head screws and cylinder head screws is high, and they are connected to common parts; the head of semi-countersunk head screws is arc-shaped, and its top is slightly exposed after installation, and it is beautiful and smooth. It is generally used for instruments or Precision machinery; countersunk head screws are used where the nail head is not allowed to be exposed. 2) The head of the hexagon socket head cap screw and the hexagon socket head flower screw can be embedded in the component, which can apply a large torque and have a high connection strength, which can replace the hexagonal bolt. It is often used in joints where compact structure and smooth appearance are required. 3) Cross recessed ordinary screws have similar functions to slotted ordinary screws, and can be replaced by each other, but the cross recessed ordinary screws have higher groove strength, are not easy to be bald, and have a more beautiful appearance. When using it, it must be loaded and unloaded with the matching cross-shaped screwdriver. 4) Lifting ring screw Lifting ring screw is a kind of hardware accessories for load-bearing during installation and transportation. When in use, the screw must be screwed in to the position where the supporting surface is tightly fitted, and tools are not allowed to be tightened, nor is a load perpendicular to the plane of the lifting ring allowed to act on it. 5) Set screws Set screws are used to fix the relative position of the parts. Screw the set screw into the screw hole of the part to be fastened, and press its end against the surface of the other part, that is, to fix the former part on the latter part. Set screws are usually made of steel or stainless steel, and their end shapes are conical, concave, flat, cylindrical and stepped. The end of the tapered or concave end set screw directly presses the parts, and is generally used in places that are not often disassembled after installation; the end of the flat end set screw is smooth and does not damage the surface of the parts after tightening, and is used for frequent adjustment of the position. At the connection, only a small load can be transmitted; the cylindrical end fixing screw is used in the fixed position that needs to be adjusted frequently, it can withstand a large load, but the anti-loosening performance is poor, and anti-loosening measures should be taken when fixing; Set screws are suitable for fixing parts with thicker walls. 6) Self-tapping screws When self-tapping screws are used on the connected parts, threads may not be pre-made at the connected parts. Use the screw to tap the thread directly when connecting. It is often used to join thin metal plates. There are two types of taper end tapping screws and flat end tapping screws. 7) Self-tapping locking screw Self-tapping locking screw not only has self-tapping effect, but also has low screw-in torque and high locking performance. Its thread is a triangular section, and the surface of the screw is hardened and has high hardness. Its thread specifications are M2 ~ M12.
The post-treatment of nickel-phosphorus plating includes two main processes of driving hydrogen and polishing. ①Hydrogen drive; according to the relevant standards, the hydrogen drive temperature after plating is 200±10℃, and the treatment time is 2h. 200 ℃ is beneficial to eliminate hydrogen embrittlement, relax internal stress, improve the bonding force between the coating and the substrate, and improve the corrosion resistance of the coating. ②Polishing; the polished bolt has a bright appearance, but in order to better improve the quality of the coating, smooth the tiny traces, and obtain a bright mirror-like surface, the coating needs to be polished with a polishing machine.
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