Fastener basics

- Jul 26, 2018 -

1. Overview: Thread is a kind of uniform spiral protrusion on the cross section of the solid surface or the inner surface. It is also the principle of applying the bevel, and it protrudes uniformly along the slope.

2. Thread category:

2.1 Classification by purpose, can be divided into fastening thread, sealing thread, transmission thread, pipe thread and special

2.2 According to the type of thread can be divided into external and internal threads.

2.3 According to the difference of the pitch, it can be divided into coarse teeth, fine teeth and ultra-fine teeth.

The fasteners produced by our company are mainly three threads in the fastening thread (general metric thread, unified thread, Wyeth thread). So focus on these three threads.

2.4 Ordinary metric thread:

a. Common teeth of coarse teeth are indicated by the letters "M" and "nominal diameter".

"M" and "nominal diameter X pitch" are indicated. The tooth angle is 60 degrees.

b. When the thread is left-handed, add “-LH” after the thread code

Example: M20 M20Χ1.5 M20-LH

c. External thread accuracy grades are: 4h, 6h and 6g, 8g; internal thread grade: 5H, 6H, 7H. (Japanese standard thread accuracy is divided into I, II, III, usually with level II). The grade currently used by our company is 6g/6H. The smaller the number, the higher the accuracy.


  • Plastic Machining Parts
  • Precision CNC Machining
  • CNC Metal Parts
  • CNC Milling Parts
  • Forged Hydraulic Cylinder Components
  • Wire EDM Works

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