Keeping It Together the Nuts and Bolts of Fasteners
KEEPING IT TOGETHER THE NUTS AND BOLTS OF FASTENERS Presented by Jim Rowe October 2011 We take fasteners and the complex system we have for identifying them by type and usage for granted. Here is some information that may help you in choosing the proper fastener for all your repair/replacement needs. Starting at the beginning, the invention of the screw thread is attributed to Archimedes in the 3rd century BC. The Archimedes Screw consisted of a cylinder with an internal continuous screw thread. When the lower end was placed into water and the cylinder rotated, water was raised to a higher level. The principle was also applied for handling light, loose materials such as grain, sand and ashes. The screws that we have today use the same technique in that a mating threaded component, rather than water, is moved through the cylinder. Sir Joseph Whitworth, a British mechanical engineer, became known for his work on engineering standards. In 1841 he proposed the introduction of standard fastener sizes to the Institution of Civil Engineers. These comprised a universal set of specifications for the angle and pitch of screw threads, the Whitworth thread became the first standard thread system in the world. Threaded fasteners are classified by shape, material and finish, which are specified by industry standards. In the United States, the American Society for Testing Materials (ASTM) sets the standards. In Europe, the International Standards Organization (ISO) sets the standards. Types of Fasteners Unified National Coarse Threads (UNC) UNC threads are the most common general fastener thread. Their fit is deeper and more generic than that of a fine thread, allowing for easy removal.
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