There are many types of threads, which can be divided into connection threads and transmission threads according to the use, triangular threads, square threads, sawn threads and circular threads according to the tooth shape, right-handed threads and left-handed threads according to the direction of the spiral, and single-wire threads and multi-wire threads according to the number of spiral wires. According to the shape of the mother, it can be divided into cylindrical thread and tapered thread.
