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