Fastener Acronyms
Fastener Acronyms can be confusing but they are a constant in the fastener world. At Albany County Fasteners we want to make your experience as simple as possible. To help you better find what you need, we have compiled a list of commonly used acronyms, what they stand for and what they mean.
Machine screws are mostly available in smaller sizes, these screws have a flat point and can be driven into a pre-tapped hole or used with a nut.UNJC+UNJFComparable to UNC and UNFSimilar to UNC and UNF in both external and internal threading. External threading on these have a much larger root radius. These larger roots lead to increased tensile stress and as a result, make them stronger. Below is a list of most of the fastener acronyms you are likely to come across.
| Acronym – Term | Description |
| AN Aeronautical Standards Group |
Precedes the dimensional specifications developed by the Aeronautical Standards Group. |
| ANSI American National Standard Institute |
The American National Standard Institute (founded 1918) was formed to create a national standard for sizing. |
| ASME American Society of Mechanical Engineers |
The American Society of Mechanical Engineers (founded 1881) was created to pursue research, education and improvement of the industry while also placing a strong emphasis on public safety. |
| ASTM American Society for Testing & Materials |
The American Society for Testing & Materials (founded 1898) aims to promote safety and health by sharing information about the reliability of different aspects in the manufacturing industry. |
| CS Countersink |
A drilled hole with a wider rim so that a screw or bolt can sit inside that area and be flush with the surface it is installed into. |
| DIN Deutsches Institut Für Normung |
Din, 1917, is the German institute for standardization. They focus on the technical and scientific creation of technical standards. |
| En-Standards (CEN) European Committee of Standardization |
CEN was created to be a mediator between the European Union and European Free Trade Association. They were to pass resolutions which both parties must adhere to. |
| FT Fully Threaded |
Threading that starts at the tip of the screw and goes all the way to the undercut of the head. |
| GR Grade |
A level of material that describes its composition. |
| HDG Hot Dip Galvanized |
A process that adds a layer of corrosion resistance by dipping fabricated steel into a kettle containing molten zinc. |
| IFI Industrial Fastener Institute |
Founded in 1931, the Industrial Fastener Institute is an association who supports standards for the mechanical fastener industry. They often develop standards when one does not exist until a national standard can be provided. |
| ISO International Organization for Standardization |
The ISO, is a federation of 158 countries from all over the world. Based in Switzerland, they propose, develop and implement new standards and then deliver them to the world. |
| LF Large Flange |
A wider surface area, often with a much greater outer diameter, than the typical surface area. Ex: Large Flange Washers. |
| MS Military Standards |
Standardized objectives created by the U.S. Department of Defense. |
| Prop 65 California’s Safe Drinking Water and Toxic Enforcement Act |
A warning label that protects Californians from chemicals which can cause long-term health defects. |
| PT Partially Threaded |
Threading that starts at the tip of a screw and stops at some point allowing for the screw or bolt to have a shoulder. |
| REACH Authorization and Restriction of Chemicals |
A European regulation created to test and determine if chemicals are safe and can be used. |
| RoHS Restriction of certain Hazardous Substances |
RoHS is a directive to restrict hazardous substances in electrical and electronic equipment. Any fastener that is a component of electrical parts and placed on the European Union market must adhere to this restriction. |
| SAE Society of Automotive Engineers |
A society, founded in 1905, to test and create standards for the automotive industry. They also develop standards for heavy-duty and aerospace vehicles. |
| SD Self Driller or Self Drilling Screws |
Primarily used to drill into steel and join materials such as sheet metal today. |
| SEMS Pre-assembled Screws |
Pre-made screw and washer assemblies. |
| SLT Slotted |
A common drive style which is also commonly called a flat head. |
| SMS Sheet Metal Screws |
Sharp threaded screws used to cut into soft metals, wood or plastics. |
| UN Thread Sizing |
A series of threading for applications where UNC, UNF, UNEF and UNS are not applicable. |
| UNEF Unified National Extra Fine |
Threads even smaller than fine threading these extra fine threads are commonly used on very small screws to make the screw stronger. |
| UNC Unified National Coarse |
Coarse threading that is the prefered thread for general use. |
| UNF Unified National Fine |
Fine threading that is not as strong as coarse threading. They do offer finer adjustments than coarse threads. |
| UNR Unified Round |
The root radius must be rounded but does not necessarily have to be inspected. |
| UNS Unified Special |
Threads that are tip(threads per inch) specified but are limited to a specific diameter. |
There are many fastener abbreviations, not all of which are listed here. Please let us know in the comments below which acronyms we forgot and help us to create a more informed fastener community!
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