To produce a thread in a hole, a profiled grooving, which follows a continuous convoluted screw line, is formed into the designated material.
This shaping can be done through cutting or grooving.
For the process of thread cutting in steel generally a tool or screw with cutting edge is used. During the cutting process chips are built, discharged and disposed. The microstructure is cut.
In the thread-forming process screws with special thread geometries and appropriate thread flank hardness are used. The thread hereby is not cut but formed. Because of this deformation process, only a very small amount of abrasion at the joining surfaces is generated, instead of chips.
During the installation in steel the hardness of the material in the thread is even slightly increased through a cold hardness increase in the joining.
An additional advantage is the tolerance-free installation because the created female thread is copying the effective dimensions of the installed screw. For having no play between male and female thread the screw is mounted firmly and dynamically safe.
Thread-forming screws by EJOT, left to right:
Formed thread in steel, JZ thread for steel, JA thread for wood.