Some knowledge about thread

Some knowledge about thread

1、 Thread Definition

Thread refers to a spiral shaped, continuous protrusion with a specific cross-section made on the surface of a cylindrical or conical base. Threads are divided into cylindrical threads and conical threads according to their parent shape;

According to its position in the parent body, it is divided into external threads and internal threads, and according to its cross-sectional shape (tooth shape), it is divided into triangular threads, rectangular threads, trapezoidal threads, serrated threads, and other special shaped threads.

2、 Related knowledge

Thread machining is a continuous protrusion with a specified tooth shape formed along the helix on a cylindrical or conical surface. A protrusion refers to the solid part on both sides of a thread.

Also known as teeth. In mechanical processing, threads are cut on a cylindrical shaft (or inner hole surface) using a tool or grinding wheel

At this point, the workpiece rotates and the tool moves a certain distance along the axis of the workpiece. The marks cut by the tool on the workpiece are threads. The thread formed on the outer surface is called an external thread. The threads formed on the surface of the inner hole are called internal threads.

The basis of a thread is the helix on the surface of a circular axis. The thread profile can be divided into various types

There are mainly several types of thread profiles:

Regular thread (triangular thread): Its tooth shape is an equilateral triangle, with a tooth angle of 60 degrees. After the internal and external threads are screwed in, there is a radial gap, which is divided into coarse and fine threads according to the size of the pitch.

Pipe thread: The tooth shape of non sealed pipe threads is an isosceles triangle, with a tooth angle of 55 degrees and a large rounded corner at the top of the tooth.

The tooth shape characteristics of sealed pipe threads are similar to those of non sealed pipe threads, but it is on the conical pipe wall, with an isosceles trapezoidal tooth shape and a tooth angle of 30 degrees.

Trapezoidal thread: Its tooth shape is an isosceles trapezoid, with a tooth angle of 30 degrees, and is widely used in screw mechanisms for transmitting power or motion.

Rectangular thread: Its tooth shape is square, and the tooth angle is equal to 0 degrees. It has high transmission efficiency, but low centering accuracy and weak root strength.

Serrated thread: Its tooth shape is an unequal trapezoidal shape, with a tooth flank angle of 3 degrees on the working surface. The root of the external thread has a large rounded corner, and the transmission efficiency and strength are higher than those of trapezoidal threads.

In addition, there are other special shaped threads, such as V-shaped threads, Whitney threads, round threads, etc. These thread profiles have their own characteristics and are selected and used according to different application scenarios.