The main types of threads include triangular threads (i.e. ordinary threads), rectangular threads,  trapezoidal threads, Serrated thread and arc threads.

  1. Triangular thread:

  Triangular threads are triangular in cross-section and are the most common threads used, so they are sometimes called common threads, which mainly include the following types: imperial threads, metric taper threads, special fine threads, transition fit threads, interference fit threads, short threads, MJ threads, small threads, 60° tapered pipe threads, and 60° thread angle.

  2. Rectangular thread:

  Rectangular threads have high efficiency and are mainly used for transmission, its cross-section is presented as rectangular, but because it is not easy to grind and it is difficult to centre the internal and external threads, so it is often replaced by trapezoidal threads.

  3. Trapezoidal thread:

  Trapezoidal thread cross-section is isosceles trapezoid, thread angle of 30. compared with rectangular thread, transmission efficiency is slightly lower, but good workmanship, high root strength, good alignment.

  4. Serrated thread:

  Serrated thread teeth working edge close to the rectangular straight edge, mostly used to withstand unidirectional axial force. The thread type mainly are (3 °, 30 °) and 45 ° thread.

  5. Arc thread:

  Its cross-section is semi-circular, mainly used for transmission, the most widely used is in the rolling screw, compared with the rectangular thread, processability, thread efficiency is higher, good alignment, many places are replacing the rectangular thread and trapezoidal thread, but because of the complexity of its fittings processing, the cost is high, so the transmission of the requirements of the application of the place of the little high.