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A Belleville washer is a type of compact, washer-shaped spring. Other terms for this item include "conical spring washer," "coned-disc spring," "cupped spring washer" and "Belleville spring." These washers are used for many applications and can be constructed out of various materials, including stainless steel. They are often used to add flexibility to bolted joints. Stacking one Belleville washer atop another in a certain orientation will influence deflection.
Belleville washers are used to solve many problems, such as thermal expansion, bolt creep and vibration-related problems. A Belleville washer is designed to generate a great amount of force in a short, compact spring design. When compressed, a coned-disc spring offers great force with minimal movement. A properly constructed Belleville washer will not relax by a significant amount even when it is under pressure for a period of time. They are designed to withstand years of regular compression without deforming.
Most Belleville washers are constructed out of grades of steel such as carbon steel and stainless steel. A type of steel called 18-8 stainless steel is one of the more popular types of stainless steel that manufacturers use to create Belleville washers. This non-magnetic type of steel contains 18 percent chromium and 8 percent nickel. Chromium and nickel add to the steel’s corrosion resistance.
Carbon steels contain more carbon than other grades of steel. They are easily stamped, forged, machined, cast and wrought into shape. Carbon increases a Bellville washer’s hardness and overall strength.
The average Belleville washer is engineered with an outer coating to increase the desirable properties of the washer’s base metal. Inorganic aluminum and zinc compound coatings contribute to increases in the washer's electrical conductivity and corrosion resistance. Most conical spring washers that are made out of carbon steel feature zinc phosphate coatings to increase corrosion resistance. Nickel plating leaves a Belleville washer with a smooth, even finish. Adding nickel plating to a washer increases the overall corrosion resistance of the spring.
Belleville washers are constructed to fit the sizes of most traditional screws. They have diameters from about 0.2-2.5 inches (4.75-63.5 mm). The diameter of the hole in the middle typically measures about 0.1-1.0 inches (2.54-25.4 mm).
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