A basic distinction is made between the soft machining and the hard machining of a tap. First of all, the blank is brought into its basic shape in the soft state by turning. Then the square is milled. Then the blank is hardened and tempered. The aim of the hardening process is to increase the mechanical resistance by specific modification and transformation of the microstructure. During hardening, the blank is heated and then cooled and heated again (tempering). The tempering process can be repeated several times.
After hardening, the hard machining of the tap begins. First the flutes are ground on a flute grinding machine. Then the thread is ground on a thread grinding machine. Finally, the chamfer is ground on a chamfer grinding machine. The processes thread grinding and chamfer grinding are carried out on modern machine tools in one clamping. Finally, the tap is marked. This is preferably done with a laser beam. Other processes and procedures are also possible.
The quality of the material used and the production processes determine the quality of the tap. There are very large differences in quality, which are manifested in particular in the following points: a material of inferior quality is processed. (tool steel instead of high-speed steel), the blank is not properly hardened and not properly tempered, the thread is only “round-ground” but not relief-ground and the rake angles are not correct, so that the tap does not cut or quickly wears out.