A screw is the most popular type of fastener used in do-it-yourself and product manufacturing. Screws can be identified by helical, or spiral, ridges wrapped around them. These threads efficiently grip or cut into wood or metal as the screw is twisted into the material. Because screws must serve as strong fasteners, they have to be made from strong materials.
Carbon Steel Wire
Screws are generally made from low to medium carbon steel wire that is rolled up on huge feeds. This material will require a cold heading machine to cut a length of wire and make two blows on the end of it to form a head. These screw blanks are then clamped to allow a cutter to create the defining threads.
Other Tough Metals
Other materials are often used instead of the carbon steel wire as they are less expensive. Materials such as stainless steel, brass, nickel alloys or aluminum alloy may be used. The quality and formation of the metal is a significantly important factor in preventing damage during manufacture or use.
More often than not, screw manufacturers will coat or plate their products to give them a greater protection and strength. This means that a screw will consist of more than one material. However, the finish applied to the screw must have a makeup compatible with the material making the screw. For instance, steel will be compatible with zinc, cadmium, nickel or chromium.
The strength of the screw is determined not only by the plating used but by the manufacturing process used. The process of threading is very important because fabricators will try to impress the thread into the screw rather than cut it out, preserving the metal and, consequently, its original strength.
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