ASME B18.12-2020 pdf download
ASME B18.12-2020 pdf download.Glossary of Terms for Mechanical Fasteners.
This Standard is a summary of mechanical fastener terminology, related characteristics, and manufacture. (a) Fastener. A fastener is a mechanical device designed specifically to hold, join, couple, assemble, or maintain equi- librium ofsingle or multiple components. The resulting assembly may function dynamically or statically as a primary or secondarycomponentofamechanismorstructure. Fasteners areusedinjustabouteverymechanicalassembly, andthey have been designed to meet the needs of products ranging from wristwatches to the space shuttle. Each fastener is produced with the degree of built-in precision and engineering capability needed to ensure adequate, sound service under preestablished environmental conditions. (b) Bolts, Studs, Screws, Nuts, Washers, Rivets, Pins, and Custom-Formed Parts. These are the general product families usedtoclassifymechanicalfasteners.Withineachproductfamilyarenumerousfasteners whosenameseitherconformto thetechnicallanguageofanationalstandardorrelateto theiroriginalapplications, e.g.,“stovebolt” or“carriagebolt.” The names given to fasteners appear to be as limitless as the imaginations oftheir designers. While manyfasteners maylook alike, each has defined engineered capabilities based upon its intended application. (c) Primary Operations. Mechanical fasteners are produced by forming or screw machine operations. (1) Forming may produce thousands of fasteners per minute with looser tolerance (depending on the size and configuration of the fastener) and typically creates minimal scrap. (2) Screwmachiningis significantlyslowerandtypicallyproduces tightertolerance buthas ahigherriskofcreating scrap.
(d) Secondary Operations. Fasteners typically undergo several secondary operations or processes, such as thread rolling, heat treating, or plating. 1.2 Referenced Documents The developers ofthis Standardwrote anumberofterms based on the language found inmore than 230 standards and other publications of the following organizations: (a) The American Society of Mechanical Headed Fastener headed fastener: a fastener that is enlarged or formed at one end. 2.1.5 Headless Fastener headless fastener: a fastener, either threaded or unthreaded, that is not enlarged at either end. 2.1.6 High-Strength Fastener high-strength fastener:afastenerwhosehightensileandshearstrengthsareattainedthroughacombinationofmaterials, work-hardening, and heat treatment. These fasteners usually have a tensile strength in excess of 120,000 psi. 2.1.7 Lock Pin and Collar lockpin andcollar:aheadedandexternallygroovedmechanicaldevicedesignedforinsertionthroughholes inassembled parts. A cylindrical collar is swaged into the external groove as the lock pin is hydraulically tensioned. Collars either are smooth bored or contain a fit-tab. An optional flange provides a built-in washer. 2.1.8 Mechanical Properties mechanicalproperties: the properties ofa fastenerin reaction to applied loads. The mechanical properties ofthe fastener are rarelythose ofthe rawmaterial fromwhich itwas made. Properties such as tensile and yield strengths, hardness, and ductility will vary widely depending on the choice of manufacturing methods and metallurgical treatments. 2.1.9 Modified Standard modifiedstandard: a standard part that has one or more ofits features or characteristics slightly changed. Such a part is typically customized to a customer’s specs for a particular application, but the change is such that any interested manu- facturer can produce the modified part. 2.1.10 Nonstandard Fastener or Special Fastener nonstandard fastener or special fastener: a fastener that differs in size, length, standardfastener: afastenerthatcanbedescribedfromnationallyrecognizedconsensus standards andmaybe produced by any interested manufacturing facility. Forexample,anorderthatspecifies 1 ∕ 2 -13 UNC-2AHexCap Screws,SAE J429 Grade5,shouldresultintheexactproduct being delivered by any fastener manufacturer accepting the order. It is often said that a standard fastener could be ordered by phone and the identical product received from multiple sources. All other fasteners are classified as SPECIAL or NONSTANDARD and may fall into the following groups: (a) modified standard (b) proprietary — patented (c) engineered special parts Generally, these require a written description and/or blueprint or drawing to communicate exactly what is required. 2.1.21 Stock Fastener stock fastener: a fastener commercially available in quantity from a manufacturer or distributor of fasteners. 2.1.22 Substandard Fastener substandard fastener: a fastener that does not meet specified requirements related to fit, form, or function. 2.1.23 Tensile Strength tensilestrength: the maximum tension-applied load afastenercan supportpriorto orcoincidentwith its fracture. Tensile strength is normallyexpressed in terms ofstress, i.e., pound-force persquare inch (psi) (U.S. Customary) ormegapascals (MPa) (SI). 2.1.24 Tension Fastener tension fastener: a fastener whose primary function is to resist forces that tend to elongate it.
