Five Basic Elements Of Screw Thread Bonding

The basic elements of the thread are: tooth type, basic size of the thread, number of lines, lead and pitch, and rotation.

 

Tooth type: the outline shape of the grain is called the thread type. The common tooth types are triangular, trapezoid, serrated and so on

 

Basic dimensions of the thread: Large diameter d (D) : The diameter of an imaginary cylinder that coincides with the tip of the external thread or the bottom of the internal thread, and is the maximum diameter of the thread.

Path d1 (D1) : An imaginary cylinder diameter that coincides with the bottom of the external thread or the top of the internal thread, and is the minimum diameter of the thread.

Middle diameter d2 (D2) : The diameter of an imaginary cylinder where the cylindrical bus passes through the grooves and bumps of equal width on the tooth profile.

Nominal diameter: represents the diameter of the thread specification, generally refers to the large diameter size of the thread. However, the nominal diameter of the pipe thread does not refer to the large diameter of the thread, but to the nominal diameter of the pipe.

 

The thread has a single line and multiple lines, the thread formed along a helix is called a single line thread, and the thread formed along two or more spiral lines distributed at equal distances in the axial direction is called a multi-line thread.

 

Lead: The axial distance between two adjacent teeth on the middle diameter line of a thread formed along the same helix.

Pitch: The axial distance between two adjacent teeth on the thread corresponding to two points on the middle diameter line.

 

Direction: The thread has right-handed and left-handed. When the thread is rotated clockwise, it is called right-handed thread; The counterclockwise rotation is called left-hand thread. Because of the application of right-hand thread, it is not necessary to indicate on the drawing; The left-hand thread must be indicated on the drawing.