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Threaded FastenersMany fasteners have threading, which are raised spiral ridges wrapping around the shaft on an angle. These threads serve to connect fasteners together and keep them attached by preventing linear motion without a corresponding rotation. They are often found on a portion of or the entire shaft of screws, bolts or nuts. Most threads are on a 60 degree angle and are either exterior (male) or interior (female). The pitch of a thread is the distance between 2 individual threads, which can be large or small. Large pitches are considered course threads, while small pitches are fine. Thread standards often include one of each. Threads are applied to fasteners by two different methods—rolling and cutting. Thread rolling involves a die with the threaded profile pressed into it. The fastener is placed between 2 dies and the thread profile is transferred via cold working, meaning the process is done around room temperature. Thread cutting is done when smaller thread diameters are needed. In this process, a rotating lathe cuts the thread pattern into the blank metal. It is much slower than the alternative rolling method, but specialized threading is easily produced by cutting. Unified standards for fastener threading are still in development. Currently, the competing metric and inch-sized thread standards are both widely used.
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