What Is The Difference between Fine Thread And Coarse Thread?

The main differences between fine thread and coarse thread are as follows：

1.Pitch size

Fine threads have a smaller pitch, which means that on a rod of the same length, fine threads have more teeth.

Coarse threads, on the other hand, have a larger pitch and relatively fewer teeth.

2.Self-locking properties

Fine-threaded screws have better self-locking properties because the smaller pitch increases the contact area between threads, providing better self-locking effects and reducing the risk of loosening.

Coarse-threaded screws have relatively poorer self-locking properties and may require additional anti-loosening measures such as spring washers or locking nuts.

3.Strength and interchangeability

Coarse threads have higher strength and better interchangeability, suitable for applications requiring significant tensile and impact forces, and it is easy to find matching bolts or nuts.

Fine threads have lower strength and poorer interchangeability, making them unsuitable for frequent assembly and disassembly, but they offer finer thread adjustment capabilities.

lead screw thread

  coarse thread VS fine thread

coarse thread VS fine thread

4.Application scenarios

Fine threads are typically used in situations requiring precise positioning, fine adjustment, high sealing, or self-locking, such as optical instruments, thin-walled parts, and precision machinery.

Coarse threads, on the other hand, are more suitable for general connections, such as in construction, automotive, and general-purpose machinery, due to their high strength and interchangeability.  

5.Installation and removal

Fine thread pitch is small, and the height of the thread is also small, making it easy for misalignment to occur during installation. Therefore, extra caution is needed when installing and removing.

Coarse threads are relatively easier in this regard and require lower precision in operation.

6.Marking rules

For fine-threaded screws, the pitch must be clearly indicated to distinguish them from coarse-threaded screws.

lead screw thread

lead screw thread

lead screw thread

For coarse-threaded screws, there is no need to specially mark the pitch, as there is only one standard pitch for coarse-threaded screws of a specific diameter.

In summary, fine-threaded screws and coarse-threaded screws differ in pitch, application scenarios, ease of installation and removal, self-locking performance, strength and interchangeability. The choice should be based on the specific requirements of the actual application.

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