How are screws, specifically their heads, manufactured? The shapes of screws are often quite complex depending on the type and head. Is the head just stamped into the screw?
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The screws start life as carbon steel wire which is straightened/pressed into a specific length/shape, the heads are formed through die pressing to whatever shape (phillips, flathead e.c.t). So essentially the top of the wire is pressed with a die that has the correct shape for the tool.
There is two methods for forming the threads, cylindrical thread forming or reciprocal thread forming. Cylindrical is where the screw is fed into multiple dies and the dies rotate around the wire to form the threads. Reciprocal thread forming uses two flat dies which are passed over the top and bottom of the wire which rotates the actual wire to form the threads.
They clip thick wire into short lengths. Each length then becomes a screw by stamping it in between molds.
The screw head is also stamped in; they grip the screw by the threads, then bash the other end with a mold that forms the mushroomed out top. The range of possible shapes for commercially produced screws is limited to what can be made in a press.
For more complex shapes that can’t be made by pressing, you would need to use a lathe and/or other precision equipment, which is much slower. Screws made this way are much more expensive and are generally only used in applications like aerospace where paying $10, $100, or even $1000 for a single screw makes sense.
This video shows two machines making screws:
[https://www.youtube.com/watch?v=C4a4IZnE98k](https://www.youtube.com/watch?v=C4a4IZnE98k)
It’s not easy to see what is happening inside the machine, but at the start of the video they show how the head is formed in two steps.
In their arrangement, after the head is finished, the threads are rolled on by a second machine.
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