Fasteners - Fasteners Chapter 18 Material taken from Mott...

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1 Fasteners Chapter 18 Material taken from Mott, 2003, Machine Elements in Mechanical Design Fastener A fastener is any device used to connect or join two or more components. The most common are threaded fasteners referred to by many names, like bolts, screws, nuts, studs, lag screws, and set screws. A bolt is a threaded fastener designed to pass through holes in the mating members and to be secured by tightening a nut from the end opposite the head of the bolt. Fastener con’t A screw is a threaded fastener designed to be inserted through a hole in one member to be joined and into a threaded hole in the mating member. The threaded hole may have been preformed, for example, by tapping, or it may be formed by the screw itself as it is forced into the material. Machine screws, or cap screws, are precision fasteners with straight-threaded bodies that are turned into tapped holes. Sheet metal screws, lag screws, self-tapping screws, and wood screw usually form their own threads.
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2 Mott, 2003, Machine Elements in Mechanical Design Mott, 2003, Machine Elements in Mechanical Design Mott, 2003, Machine Elements in Mechanical Design
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3 Bolt Materials and Strength In machine design, most fasteners are made from steel because of its high strength, high stiffness, good ductility, and good machinability and formability. But varying compositions and conditions of steel are used. The strength of steels used for bolts and screws is used to determine its grade, according to one of several standards. Bolt Materials and Strength con’t Three strength ratings are frequently available: the familiar tensile strength and yield strength plus the proof strength. The proof strength, similar to the elastic limit, is defined as the stress at which the bolt or the screw would undergo permanent deformation. It usually ranges between 0.90 and 0.95 times the yield strength. The SAE uses grade number ranging from 1 to 8, with increasing numbers indicating greater strength. Mott, 2003, Machine Elements in Mechanical Design
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4 Mott, 2003, Machine Elements in Mechanical Design Bolt Materials and Strength con’t Aluminum is used for its corrosion resistance, light weight, and fair strength level. Its good thermal and electrical conductivity may also be desirable. Brass, copper, and bronze are also used for their corrosion resistance. Alloys used for fasteners include 18-8, 410,
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Fasteners - Fasteners Chapter 18 Material taken from Mott...

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