We often encounter the problem of coarse thread and fine thread in the machining process, so what is the difference between them and how to choose? Let's make a brief introduction.

Coarse Thread
Coarse thread actually refers to the standard thread. Without special instructions, the stainless steel screws and other fasteners we generally buy are coarse threads.
Coarse thread is characterized by high strength, good interchangeability, and there are standards for comparison. Generally speaking, coarse thread should be the best choice; Compared with the fine thread, the coarse thread has a large thread pitch and a large thread lift angle, and the self-locking performance is poor. In the vibration environment, it is necessary to install anti-loose washers, self-locking devices, etc.; its advantage is that it is easy to disassemble and assemble. The matching standard parts are complete and easy to be interchanged; when the coarse thread is marked, it is not necessary to mark the pitch, such as M8, M12-6H, M16-7H, etc., which are mainly used for connecting threads.

Fine Thread
The fine thread and the coarse thread are just the opposite, it is stipulated to supplement the special use requirements that the coarse thread cannot meet. 
The fine thread also has a pitch series. The pitch of the fine thread is smaller, so it is more conducive to self-locking and anti-loosening, and the number of teeth is more, which can reduce the effect of leakage and achieve the effect of sealing. In some precise occasions, fine-toothed stainless steel screws are more convenient for precise control and adjustment.
The disadvantage of the fine thread is that the tensile value and strength are lower than that of the coarse thread, and the thread is easily damaged. It is not recommended to disassemble and assemble it multiple times. The matching nuts and other fasteners may be equally accurate. If there is a slight error in the size, it is easy to make The screws and nuts are damaged at the same time. It is mainly used in metric pipe fittings of hydraulic system, mechanical transmission parts, thin-walled parts with insufficient strength, internal parts limited by space and shafts with high self-locking requirements. The pitch of the fine thread must be marked to show the difference from the coarse thread.

How to choose coarse thread and fine thread?
Coarse thread screws and fine thread screws are used for fastening. Fine thread screws are generally used to lock thin-walled parts and parts with high requirements for anti-vibration. Fine thread has good self-locking performance, so it has strong anti-vibration and anti-loosening ability, but due to the shallow depth of the thread, the ability to withstand greater tension is worse than that of coarse thread. When no anti-loosening measures are taken, the anti-loosening effect of fine thread is better than that of coarse thread, and is generally used for thin-walled parts and parts with high requirements for anti-vibration. When used for adjustment, the fine thread is more advantageous. Disadvantages of fine thread: It is not suitable for application on materials with excessively thick tissue and poor strength. When the tightening force is too large, it is easy to slip.

Dongguan Yejia Precision Machinery Co., Ltd. has CNC large-scale gantry machining centers, CNC machining centers, precision CNC milling machines, lathes, large surface grinders, precision shape correction machines, CMM three-coordinate measuring machines, electronic altimeter and other advanced manufacturing and testing equipment more than 90 sets.The maximum size that can be processed is 5000×3200×1000mm, and the machining accuracy can reach 0.002.

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