How To Choose Between Coarse and Fine Threads?
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How To Choose Between Coarse and Fine Threads?
How fine is a thread to be called a fine thread? We might define it in this way. The so-called coarse thread can be defined as a standard thread, while the fine thread is relatively coarse. Under the same nominal diameter, the number of teeth per inch is different, that is, the pitch is different. The pitch of the teeth is large, and the pitch of the fine teeth is small. In other words, for the 1/2-13 and 1/2-20 specifications, the former is coarse and the latter is fine. Therefore, it is expressed as 1/2-13UNC and 1/2-20UNF.
Since there are two different thread specifications for the same nominal diameter, how to choose between coarse and fine threads?
Coarse thread
The so-called coarse thread actually refers to the standard thread. Unless otherwise specified, the stainless steel screws and other fasteners we generally buy are all coarse threads.
Coarse threads are characterized by high strength, good interchangeability, and standards for comparison. Generally speaking, coarse threads should be the best choice.
Compared with fine thread, coarse thread has poor self-locking performance due to its larger pitch and higher thread lift angle. It is necessary to install anti-loosening washers, self-locking devices, etc. in a vibration environment. The advantage of coarse thread is that it is easy to disassemble and assemble, and the standard parts matched with it are more complete and easy to exchange.
Coarse threads do not need to be marked with pitch, such as M8, M12-6H, M16-7H, etc., which are mainly used for connecting threads.
Fine thread
Fine thread and coarse thread are just the opposite. They are specified to supplement the special use requirements that coarse thread cannot meet. There are also pitch series for fine thread. The pitch of 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 precision occasions, fine-tooth stainless steel screws are more convenient for precise control and adjustment. The disadvantage is that the tensile value and strength are relatively low, and the thread is easy to damage. It is not recommended to disassemble and assemble multiple times. The matching nuts and other fasteners may be equally accurate, and the size is slightly wrong, which will easily damage the screws and nuts at the same time.
Fine thread is mainly used in metric pipe fittings of hydraulic systems, mechanical transmission parts, thin-walled parts with insufficient strength, internal parts restricted by space, and shafts with high self-locking requirements. When marking fine thread, the pitch must be marked to show the difference from coarse thread.
How is the thread processed?
Generally refers to the method of machining threads on a workpiece with a machining tool or an abrasive tool. There are many thread processing methods, mainly including turning, milling, tapping, threading, grinding, rolling, and so on. They each have different characteristics and must be selected according to factors such as the shape, size, output, and technical requirements of the parts. Because there are many kinds of threads, there are many kinds of thread-turning inserts. Our can provide you with a complete range of threading carbide inserts. Any inquiries, just contact us to get more details.
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