Fastener coarse thread and fine thread, how to choose?

Release time:

2021-10-12

How to choose coarse and fine thread Coarse thread and fine thread screws are used for fastening. Fine tooth screws are generally used to lock thin-walled parts and parts with high anti-vibration requirements. The fine thread has good self-locking performance, so it has strong anti-vibration and anti-loosening ability. However, due to the shallow depth of the thread, the ability to withstand greater tension is worse than that of the coarse thread. When no anti-loosening measures are taken, the anti-loosening effect of fine thread is better than that of coarse thread. It is generally used for thin-walled parts and parts with high anti-vibration requirements. When doing adjustment, fine thread has more advantages. 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.

Fastener coarse thread and fine thread, how to choose?

We might as well define this, the so-called coarse thread, can be defined as a standard thread; and fine thread is relatively coarse, in the same nominal diameter, the number of teeth per inch is different, that is, the pitch is different, the pitch is large, and the pitch is small. In other words, for the 1/2-13 and 1/2-20 specifications, the former is coarse teeth and the latter is fine teeth. Thus expressed as 1/2-13UNC and 1/2-20UNF.

Since there are two different thread specifications for the same nominal diameter, how to choose coarse thread and fine thread?

coarse thread

The so-called coarse teeth actually refer to standard threads. Without special instructions, the stainless steel screws and other fasteners we generally purchase are coarse teeth.

Coarse thread is characterized by high strength, good interchangeability, and there are standards to control, generally speaking, coarse teeth should be the best choice;

Compared with fine thread, due to the large pitch, the rising angle of the thread is also large, and the self-locking property is poor. In the vibration environment, it is necessary to install lock washers, self-locking devices, etc.; the advantages are convenient disassembly and assembly, and the standard parts matched with it Complete, easy to exchange;

Coarse thread does not need to be marked with pitch, such as M8, M12-6H, M16-7H, etc., which are mainly used for connecting thread.

fine thread

Fine teeth and coarse teeth are just the opposite, which are stipulated in order to supplement the special use requirements that cannot be met by coarse thread. Fine thread also has pitch series, and the pitch of fine teeth is smaller, so it is characterized by more self-locking and anti-loosening, and more teeth, which can reduce leakage and achieve sealing effect. In some precision occasions, stainless steel screws with fine teeth are more convenient for precise control and adjustment.

The disadvantage is that the tensile value and strength are lower than the coarse teeth, and the thread is easy to be damaged. It is not recommended to disassemble and assemble many times. The matching nuts and other fasteners may be equally accurate, with a slight error in size, which is easy to damage the screws and nuts at the same time.

Fine thread is mainly used in the hydraulic system of the metric pipe fittings, mechanical transmission parts, the strength of the lack of thin-walled parts, subject to space constraints and self-locking requirements of the higher shaft. Fine thread must be marked with pitch to show the difference with coarse thread.

How to choose coarse and fine thread

Coarse thread and fine thread screws are used for fastening.

Fine tooth screws are generally used to lock thin-walled parts and parts with high anti-vibration requirements. The fine thread has good self-locking performance, so it has strong anti-vibration and anti-loosening ability. However, due to the shallow depth of the thread, the ability to withstand greater tension is worse than that of the coarse thread.

When no anti-loosening measures are taken, the anti-loosening effect of fine thread is better than that of coarse thread. It is generally used for thin-walled parts and parts with high anti-vibration requirements.

When doing adjustment, fine thread has more advantages. 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.

Source: Fastener Industrial Network