Except for the pipe thread whose nominal diameter is the internal diameter of straight pipe (English unit), the nominal diameter of other threads is the major diameter of external thread (metric unit). Taking the common metric external thread as an example, the tooth profile angle of the common metric thread is 60.
The following is an introduction to threaded applications:
The invention relates to a processing method for obtaining the plastic deformation of a threaded workpiece by forming a rolling die. Wire rolling is generally carried out on a wire rolling machine. The thread rolling machine is carried out on an automatic lathe with an automatic thread rolling head, which is suitable for mass production of external threads of standard fasteners and other threaded connectors.
Generally, the outer diameter of the rolled thread is not more than 25mm, the length is not more than 100mm, the thread accuracy can reach Grade 2, and the diameter of the blank used is roughly equal to the middle diameter of the processed thread. Generally, internal thread cannot be processed by rolling, but for soft workpiece, internal thread can be cold extruded by slotless extrusion tap, and its working principle is similar to tapping. The torque required for cold extrusion of internal thread is about 1 times that required for tapping, and the machining accuracy and surface quality are slightly higher than tapping.
The advantages of wire rolling are: the surface roughness is less than that of turning, milling and grinding; Due to cold working hardening, the strength and hardness of the rolled thread surface can be improved; High material utilization rate; The productivity is doubled than that of cutting, and it is easy to realize automation.
The rolling die has long service life. However, rolling thread requires that the hardness of workpiece material should not exceed HRC40；; It requires high dimensional accuracy of the blank; The precision and hardness of the rolling die are also high, and it is difficult to manufacture the die; Not suitable for asymmetrical thread of hobbing.
Refer to Baidu Encyclopedia -Thread for the above information.