Rolling is a process of forming the threaded part of a screw. This operation comes after the manufacturing of the blank. The latter, still smooth, is introduced between 2 combs having the shape of the negative thread. Passing the still smooth part between these 2 combs (one fixed and one mobile) will make it possible to obtain the threaded part.
Performed in-line after striking or as a rework operation, threading is the most sensitive part of making a screw