What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Screws are a kind of fasteners commonly used in daily life and industry. At present, in use, different types of screws are generally selected for fixing according to different screw lengths and other parameters. Since the screw length is fixed at the time of manufacture, when When using a large number of screws with different screw lengths, it is necessary to sort out screws with different screw lengths beforehand. This method is more troublesome, and sometimes in some special occasions, some screws with special lengths are required. Producing screws of this particular length individually is laborious and laborious.
People often think that magnets attract stainless steel to verify its pros and cons and its authenticity. If it does not attract non-magnetism, it is considered to be good, and it is genuine; if it is magnetic, it is considered to be counterfeit. In fact, this is an extremely one-sided, unrealistic and wrong identification method. There are many kinds of stainless steel screws, which can be divided into several categories according to the organizational structure at room temperature: 1. Austenite type: such as 304, 321, 316, 310, etc.; 2. Martensite or ferrite type: such as 430, 420, 410, etc.; Austenite type is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Most of the stainless steel usually used for decorative tube sheets is austenitic 304 material, which is generally non-magnetic or weakly magnetic, but may also appear magnetic due to fluctuations in chemical composition or different processing conditions caused by smelting, but this cannot be considered as a Counterfeit or substandard, what is the reason for this? As mentioned above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to component segregation or improper heat treatment during smelting, a small amount of martensite or ferrite in austenitic 304 stainless steel will be caused. body tissue. In this way, 304 stainless steel will have weak magnetism. In addition, after cold working of 304 stainless steel, the structure will also be transformed into martensite. The greater the cold working deformation, the more martensite transformation, and the greater the magnetic properties of the steel. Like a batch of steel strips, Φ76 tubes are produced without obvious magnetic induction, and Φ9.5 tubes are produced. The magnetic induction is more obvious due to the large deformation of the bending and bending. The deformation of the square rectangular tube is larger than that of the round tube, especially the corner part, the deformation is more intense and the magnetic force is more obvious. In order to completely eliminate the magnetic properties of 304 steel caused by the above reasons, the stable austenite structure can be restored by high-temperature solution treatment, thereby eliminating the magnetic properties. In particular, the magnetic properties of 304 stainless steel caused by the above reasons are completely different from those of other materials such as 430 and carbon steel, which means that the magnetic properties of 304 steel always show weak magnetic properties. This tells us that if the stainless steel strip is weakly magnetic or completely non-magnetic, it should be judged as 304 or 316 material; if it is the same as carbon steel, it shows strong magnetism, because it is judged as not 304 material.
Round head three-combination screw The screw size in the round-head three-combination screw is GB818, and the main technical requirements of various types are: iron and stainless steel material requirements, iron low, medium, high carbon steel, stainless steel combination The materials of the screws are stainless steel 201, stainless steel 304 and stainless steel 316. The thread tolerance is 6G, and the mechanical properties of the iron combination screws are 4.8 and 8.8. The 4.8-level combination screws are ordinary steel, and the maximum allowable hardness is 255HV. The 8.8-level combination screws are generally made of wire rod 10B21. , and then undergo hardening treatment, and then dehydrogenation after hardening treatment. Hydrogen removal is to prevent hydrogen embrittlement of the spring washer in the combination screw. Prevent the spring pad from breaking. The tolerance class of the combination screws is A. The cross groove is H-shaped. The surface treatment of the combination screw has environmental protection and non-environmental protection. Such as, environmental protection blue zinc, environmental protection color zinc, black zinc, color zinc, white nickel and so on. The technical requirement of the combination screw for the spring washer is that the washer should be able to rotate automatically without falling off.
For achieving the above purpose, Guangdong Yueluo Hardware Industry Co., Ltd. provides the following technical solutions: a pin, comprising a pin cap and a described pin rod, the pin cap and one end of the pin rod are fixedly connected, and the pin rod There is a convex body, the convex body is fixedly connected with the pin rod, the convex body is located on the pin rod rod body, and the other end of the pin rod is provided with a top connecting body, and the top connecting body is fixedly connected with the pin rod , the top contact body includes several top contact units and discs, each top contact unit is coaxially arranged with the pin rod, the top contact units are sequentially fixedly connected along the axis direction of the pin, the top contact unit is The major diameter of the outer contour of the connecting body is larger than the diameter of the pin rod.
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