What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The marking format of the thread mark is: Thread code - thread tolerance zone code (pitch diameter, top diameter) - screw length l) Tolerance zone code is represented by numbers plus letters (inner thread with uppercase letters, external thread with lowercase letters) , such as 7H, 6g, etc., it should be specially pointed out that 7H, 6g, etc. represent thread tolerance, while H7, g6 represent cylinder tolerance code. 2) The length of rotation is specified as short (represented by S), medium (represented by N), and long (represented by L). In general, the thread engagement length is not marked, and the thread tolerance zone is determined by the medium engagement length (N). If necessary, add the screw length code S or L, such as M20-5g6g-L. When special needs are required, the value of the screwing length can be indicated, such as M20-5g6g-30.
The equipment is tightened and fixed by screws during assembly. During high-speed operation, the equipment will generate high-frequency micro-vibration. This micro-vibration can easily lead to loosening of screws, resulting in weak connection of components and easy to cause safety accidents. Fastening is attached great importance. Many companies even directly weld the screw caps after using screws to fasten the components. However, this practice greatly hinders the subsequent maintenance and also seriously affects the maintenance and maintenance of the equipment; The emergence of tightening screws has attracted the attention and favor of enterprises; however, the self-tightening screws I use are mainly imported, and when the trade war begins, the shortage of this autonomous technology will severely limit my defense.
Nuts are parts that tightly connect mechanical equipment. Through the inner thread, nuts and bolts of the same specification can be connected together. At present, most nuts are used together with gaskets when they are locked, or are set as an integrated structure, which has the advantage of increasing Friction, strengthen the effect of tightening, but the square nut is usually used directly without adding a gasket, and the upper and lower end faces are flat, very smooth, when subjected to strong vibration, it is very easy to loosen, and the tightening effect is not good.
T-slot bolts refer to the bolts installed in the T-slot. The installation process of T-slot bolts is usually as follows. When the T-slot (generally refers to the T-slot aluminum alloy profile) is set horizontally, the bolt The bolt head is placed in the T-slot in the horizontal direction, the bolt shaft is facing outward, and then the bolt is rotated 90 degrees axially, the bolt head becomes vertical and will not come out of the T-slot, and then install the mounting hole of the object Align the bolt rod and insert it and screw the nut on the bolt rod. During the tightening process of the nut, if the thread gap is small or the thread is damaged or there is dirt, the bolt will often rotate, and the rotation angle of the bolt is uncontrollable and impossible. Observe that when the rotation angle of the bolt is in the range of about 90 degrees, the bolt is in a state of being released from the T-shaped groove at any time. Even if the nut is tightened, the installation of the installation object is invalid and unreliable, and there is a serious safety hazard. , the actual situation is that when the rotation angle of the bolt exceeds 20-30 degrees, the installation of the installation object is already unreliable.
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