There are two different manufacturing processes for making screws. Most screws are made with the thread rolling method. Machining is used to make small or specialized screws that cannot be made by thread rolling.
The first step in making a screw with the thread rolling method is called “cold heading.” A wire is fed into a machine to straighten it, then cut it to length. The machine then cuts the head into the desired shape.
There are three techniques that can be used to cut the blank screw to give it threading:
Reciprocating die: There are two flat dies — one is stationary, and the other moves back and forth. The screw is rolled between the two dies.
Centerless cylindrical die: The screw is rolled between two or three round dies to create the thread.
Planetary rotary die: As the screw is held stationary, several die-cutting machines spin it around.
Between these two screw manufacturing processes, thread rolling is better. The screws are more durable and high quality, avoiding weaknesses in the metal. The screw threads are placed precisely as well, so all screws are the same.