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alloy-steel
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A type of steel that contains additional elements to improve the properties of a fastener.
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aluminum
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A silvery, white metal that is soft, light, and is electrically and thermally conductive.
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bending load
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A force that is applied in the middle or on the end of an object causing the object to bend in a curve.
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bolt fracture
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A type of fastener failure that occurs when a fastener is over-tightened and causes the bolt to break.
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Brinell scale
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A method for testing a material's hardness that forces a hard steel sphere under a specified load into the surface of a material and measuring the diameter of the indentation left after the test.
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bronze
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An alloy of copper and tin. Bronze is highly corrosion resistant.
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carbon steel
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A type of steel made up of iron and carbon and no other material. Most fasteners are made from carbon steel.
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clamping force
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The compressive force that a fastener exerts on a joint.
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cold working
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The shaping of metal at temperatures much lower than the metal's molten state. Cold working increases the strength in certain steels.
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compression load
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A pushing or pressing force that is directed toward the center of an object.
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copper
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A reddish-brown metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper fasteners are often used for electrical components.
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corrosion
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The gradual chemical attack on a metal by atmosphere, moisture, or other agents.
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corrosion resistance
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The ability of a material to resist chemical destruction from an environment. Corrosion resistance is the most important physical property for fasteners.
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density
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The relative compactness of a material. Density is the mass of a material per unit volume.
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ductility
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The ability of a fastener material to deform before it fractures.
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elastic limit
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The maximum stress a material can support before it deforms. Elastic limit is also known as yield strength.
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electrical conductivity
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The ability of a material to conduct an electrical current.
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elongate
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To extend the length of an object.
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fatigue
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A type of fastener failure that occurs when a fastener is subjected to repetitive loading or stressing. Fatigue can cause catastrophic failure.
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fatigue strength
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The maximum stress a fastener can withstand for a specific number of repeated applications prior to its failure.
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ferrous
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A metal that contains iron. Carbon steels are common ferrous metals.
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grade
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A category that fasteners are grouped in according to their strength.
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grade identification
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The marking on the head of a bolt that indicates tensile strength.
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hardness
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The measure of a fastener's ability to resist penetration, indentation, and scratching
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heat treatment
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The heating and cooling processes used to change the structure of a material and alter its mechanical properties.
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hex-head bolt
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A type of bolt that has a head with six sides.
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indenter
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A device used in a hardness test that is pressed into the test material.
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load
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The overall force that is applied to a material or structure. A fastener that supports the weight of an object is withstanding a load.
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low-carbon steel
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A type of carbon steel that contains less than 0.3% carbon. Grade 2 fasteners are common low-carbon steel fasteners.
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mechanical properties
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The properties that describe the way a material responds to forces that attempt to bend, break, twist, dent, or scratch it. Mechanical properties are the most important properties for fasteners.
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medium-carbon steel
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A type of carbon steel that contains between 0.3% and 0.5% carbon. Grade 5 fasteners are common medium-carbon steel fasteners.
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megapascal
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The metric unit of pressure. Megapascal is abbreviated Mpa.
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nonferrous
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A metal that does not contain iron. Aluminum, copper, and zinc are nonferrous metals.
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non-threaded fastener
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A type of fastener that does not contain threads. Pins, retaining rings, and rivets are examples of non-threaded fasteners.
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off-torque
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The force that is proportional to torque in the opposite manner. An off-torque condition causes the fastener to rotate loose.
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overloading
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A type of fastener failure that occurs when an excessive load is applied to a bolt, which causes the bolt to yield or fracture.
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permanent deformation
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The stress that causes a fastener to lose its original shape and appearance.
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physical properties
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The properties that describe the way a material responds to external environment conditions, such as temperature, chemical exposure, and electricity. Corrosion resistance is the most important physical property for fasteners.
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pounds per square inch
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A unit of pressure that measures the amount of load pressure per inch. Pounds per inch is abbreviated psi, or pounds per square inch.
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preload
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The tension created in a fastener when it is first tightened. Preload must be greater than the external forces applied to the assembly to prevent joint failure.
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proof load
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The amount of stress that the fastener can withstand without experiencing deformation. Proof load is often used interchangeably with yield strength.
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properties
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The characteristics of a material that distinguish it from other materials.
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protective coating
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A layer applied over metal that contains elements, which prevent the metal from damage.
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Rockwell scale
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A method for testing a material's hardness that uses an indenter to test the material's resistance to deformation as a load is applied.
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shear strength
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The ability of a fastener material to resist internal sliding.
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shearing
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The cutting and separating of material through its cross section.
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socket screw
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A type of capscrew with a round head and a hexagonal indentation for tightening purposes.
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strength
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The ability of a material to resist stress caused by forces attempting to break or deform the material.
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stress
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The applied force over a certain area that tends to deform an object or structure.
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stud
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An externally threaded fastener that is often threaded at both ends and can be used with a nut. Unlike bolts, studs do not have a head.
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synthetic
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Something that is produced artificially. Synthetic materials include plastic and nylon.
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tensile strength
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The maximum stress a fastener can endure before it breaks. Tensile strength is the most important property associated with threaded fasteners.
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tension load
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A pulling force that is directed away from the object and attempts to stretch or elongate the object.
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thermal conductivity
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The ability of a material to conduct heat.
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thermal expansion
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The tendency of a material to increase in size as it increases in temperature.
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thread stripping
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A type of fastener failure that occurs when a fastener is over-tightened. Thread stripping causes the fastener threads to appear deformed.
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threaded fastener
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A type of fastener that contains threads. Bolts, screws, and nuts are examples of threaded fasteners.
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tolerance
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The unwanted but acceptable deviation from a specified dimension.
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torque
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The amount of force applied to tighten a bolt, screw, or nut.
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torsion test
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A test that involves twisting an object to test a material's shear strength.
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torsional load
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A force that is applied by clamping one end of an object and twisting the other.
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torsional strength
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The ability of the fastener to resist a torque that attempts to twist a fastener off its axis.
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traceability
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The ability to trace the history, application, or location of an item using documentation.
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ultimate tensile strength
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The final amount of stress sustained in a tensile test at the exact moment the object ruptures.
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vibration loosening
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A type of fastener failure that occurs in a bolted joint due to excessive motion, which causes the bolt to rotate loose.
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Vickers scale
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A method for testing a material's hardness that uses a pyramid-shaped diamond to exert pressure on the surface of a material for a standard length of time. The diagonal of the indentation is measured under a microscope to determine the hardness value.
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washer
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A flat disc with a hole through the center that is often used with threaded fasteners to ensure tightness of the joint.
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wedge tensile test
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A procedure used to test tensile strength in which a washer with a beveled surface is placed under the head of a fastener causing a bending stress.
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yield strength
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The maximum force that a fastener can withstand before it experiences permanent deformation.
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