Thread rolling is a method to obtain thread by forming a rolling die to produce plastic deformation of the workpiece. Thread rolling is usually carried out on a wire rolling machine, a wire rolling machine, or an automatic lathe with an automatic opening and closing thread rolling head. Thread rolling is suitable for mass production of standard fasteners and other threaded couplings for external threads.
The outer diameter of the rolled thread is generally no more than 25 mm, and the length is no more than 100 mm. The precision of the thread can reach 2 grades (gb197-63). Generally, the rolling pressure cannot process the inner thread, but for the workpiece with soft material, the grooveless extrusion tap can be used to cold-press the inner thread (the maximum diameter can reach about 30mm), and the working principle is similar to the tapping. The torque required for cold extrusion of internal threads is about one time larger than that of tapping, and the machining precision and surface quality are slightly higher than tapping.
- The surface roughness is smaller than that of turning, milling and grinding;
- The surface of the thread after rolling can increase strength and hardness due to cold hardening;
- High material utilization rate; Productivity is multiplied than cutting, and it is easy to automate.
- Rolling die has a long life. However, rolling thread requires that the hardness of workpiece material should not exceed HRC40.
- High requirements on the precision of the blank size;
- High requirements on precision and hardness of rolling mould are also required, making it difficult to make thread rolling mould.
- It is not suitable for rolling asymmetrical thread of tooth shape.