Threads are divided into cylindrical threads and conical threads according to their mother shapes; According to its cross-sectional shape (tooth type), it can be divided into triangular thread, rectangular thread, trapezoidal thread, serrated thread and other special shapes. Triangular threads are mainly used for connection, while rectangular, trapezoidal and serrated threads are mainly used for transmission. According to the spiral direction, it is divided into left-handed thread and right-handed thread, which is generally used; According to the number of threads, it can be divided into single thread, double thread and multi-thread thread; Most connections are single-wire, and transmission is double-wire or multi-wire; According to the size of teeth, it can be divided into coarse thread and fine thread.

# Cylindrical thread # Tapered thread # Triangular thread # Rectangular thread # Trapezoidal thread # Sawtooth thread # Left thread # Right thread # Single thread # Double thread # Multi thread # Coarse thread # Fine thread