Five-axis machining of non-standard threads
 
1. Standard thread: thread whose tooth type, diameter and pitch are all in line with national standards. The pipe thread standard is derived from the British Wyeth thread, which is the basic size to measure the size of the pipe thread. Usually according to the 1/16 taper relationship, the radial diameter tolerance of the Wyeth thread is converted into the axial tooth number tolerance of the British seal pipe thread.

2. Special threads are also called special-shaped threads, which are different from ordinary threads. Special-shaped thread refers to a thread with a special shape such as the outer contour and tooth profile of the thread. Such as: special-shaped thread on cylindrical surface, arc surface and non-circular surface. The profile of the special-shaped thread is triangle, rectangle, trapezoid, arc, conic (ellipse, parabola, hyperbola) and so on.

3. Non-standard thread: thread type, diameter or pitch, one of which does not meet the national standard.

Extended information
1. British pipe thread comes from British Wyeth thread. The combination of the Wyeth thread pipeline series and the Wyeth thread profile establishes the basic size of the British pipe thread. According to the 1/16 taper relationship, the radial diameter tolerance of the Wyeth thread is converted into the axial tooth number tolerance of the British seal pipe thread (there is a certain amount of rounding and adjustment).
2. There are two matching methods for British sealed pipe threads: "column/cone" and "cone/cone". The two British seal pipe threads use different thread ring gauges (cylindrical thread ring gauge and tapered thread ring gauge) and thread plug gauge (the position of the datum plane is different, and the two datum planes are half a tooth apart). European countries, mainly "column / cone" mating thread; and countries outside Europe mainly a "cone / cone" mating threads.