Keywords:how to choose the thread thickness

For those who know a little about bolts, I’m afraid they all know that in addition to the size of the thread, there is also the difference between coarse teeth and fine teeth. Even if the same size, if a thick tooth and a fine tooth, or can not be used together. The so-called, different ways do not conspired with each other.

how to choose the thread thickness 

So, how to choose thick teeth fine teeth?

Let’s first look at where the metric teeth come from. As we know, the British Empire with its strong industrial strength, its dominant inch thread also once dominated the world. In fact, imperial thread was also divided into coarse and fine teeth, and the siege lions of that time probably had different opinions about which to choose. Later, when creating metric threads, a compromise was chosen, in which the coarse thread of the metric thread was actually a thread between the inch coarse and fine thread.


But later the metric thread also developed fine teeth, in which the Japanese and Korean models in the majority.


The so-called thick teeth fine teeth, not to say that the thread is thick and fine, but that the thread spacing is different, the tooth spacing of fine teeth is smaller, so it looks like the thread teeth are “fine” some.

how to choose the thread thickness

So what are the advantages of thick teeth and fine teeth?

  • More robust, reducing the risk of tooth loss during assembly;
  • Can accommodate minor abnormalities in the manufacturing process;
  • Faster assembly and disassembly;
  • Higher coarse tooth strength when assembled with low strength nuts or internal threads;
  • Greater tolerance for inappropriate manual assembly;
  • Can accommodate thicker plating;
  • Easier to penetrate brittle materials;
  • Greater sliding strength with the same number of meshing threads
  • More common thread spacing.

After bragging about thick teeth, let’s talk about the advantages of fine teeth.

  • Axial is better for neutral;
  • Can increase thread strength without increasing thread size;
  • When the thickness is limited, can effectively increase the thread length of engagement;
  • Smaller helix Angle, so the same torque can produce more clamping force, not easy to loosen;
  • Larger path, so higher torsional and shear strength;
  • Easier penetration of thin-walled and hard materials;
  • Incomplete thread under bolt head is smaller.
  • So since each has his own merits, how to choose thick teeth and fine teeth?


The engineer of Yijin Hardware to think, when the main thick teeth, fine teeth as auxiliary.


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