A.. Glossary of Fastener and Fixing Terminology

fastener nomenclature

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Stainless steel A2 used in the production of fasteners and fixings is also called type 304 and 18.8 It contains 18% Chromium and 8% nickel.  A2 is an austenitic steel and is non-magnetic. The chromium provides a corrosion and oxidation resistance, however, it can tarnish. Stainless steel A2  property classes for fasteners are 50, soft or 70 cold-worked. 


Stainless steel material A4 is also called type 316 and is required for marine conditions where you need more resistance to corrosion. Adding molybdenum (2-3%) to the mix provides this extra resistance.

A4 grade is austenitic, non-magnetic, the molybdenum increases the corrosion resistance to withstand attack from many industrial chemicals and solvents and chlorides.

A4 grade stainless steels come in property classes: 50, soft and 80 high-strength


Acme thread is a screw thread having a 29 degree included angle. Used largely for feed and adjusting screws on machine tools. Products


Nut shaped like an acorn it has a hexagon base and a domed top that it prevents contact with the threads, Products.


All metal prevailing torque locking nut. The nut is slotted in two places on the top after the nut has been tapped the slots, are bent slightly inwards and downwards.

When the nut is screwed onto the bolt thread the two slotted parts are forced back to their original position.

Their stiffness causes the nut threads to bind onto the bolt threads and provides prevailing torque locking. Products


The change in the property of a metal when treated to remove it from an unstable condition. Treatment types are quenching, cold working or hardening.


A process of heat hardening and controlled air cooling; mainly used with tool steels and stainless steel. Modern air-hardening steels are characterised by low distortion during heat treatment because of their high-chromium content. Their machinability is good and they have a balance of wear resistance and toughness 


The historical generic name for a socket screw. Internal hexagon socket screws have a long history from cold forming of the first mass-produced socket products in 1910 by William Allen, through to modern day manufacture around the globe.

Allen, acquired by Holo-Krome in 1986 is no longer a force in the socket screw market; like Hoover is to vacuum cleaners the name has become part of the Global fastener language Product


To differentiate from low carbon steels with low or no Alloy content against steels with high Alloy content. Alloys change the performance of the steel in strength, corrosion resistance and other properties demanded by the market.


Round bar threaded for its full length, also called Studding, Is available in all thread types and grades.  Product


Adhesive which hardens in the absence of air, such adhesives are often applied to threads, as the threads tighten the air is excluded.

Primarily used as a thread locker. Products


The Anco nut is extensively used in the petrochemical industry, it is an all-metal self-locking nut with a stainless steel ratchet pin. A Lok-Mor ® patented nut with a non-breakable Stainless Steel Pin. The nut prevents the removal of coatings, damage to the bolt threads and the unique controlled lock indention ensures consistent locking torque.  Product


Tightening procedure in which a fastener is first tightened so that the clamped surfaces are pulled together, it is tightened further by giving the nut an additional measured rotation such as a 1/2 turn or more. 

Frequently bolts are tightened beyond their yield point by this method in order to ensure that a precise preload is achieved.

Using this method, bolts of short length can be elongated too much and the bolt material must be sufficiently ductile to cater for the plastic deformation involved. Because of the bolt being tightened beyond yield, its re-use is limited.


Heating and controlled cooling of steel to remove stress and changing its ductility, this is a prerequisite to cold forging. 

This process removes internal stresses in the fasteners and makes the material more ductile and pliable. The process consists of heating the fasteners to a selected temperature depending upon specification, followed by a slow and carefully regulated cooling to allow the material to stabilise. 


Anodising (UK)  Anodizing (USA) is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.  More detail

ANSI  American National Standards Institute

The American National Standards Institute is a private non-profit making organisation that oversees the development fastener product standards in the United States. see standards


Anti-friction coatings are dry lubricants consisting of suspensions of solid lubricants, such as graphite, PTFE or molybdenum disulphide in a binder. Anti-friction coatings can be applied to fastener threads to replace metallic coatings such as zinc and cadmium and offer maintenance-free permanent lubrication.

By careful selection of the lubricants, anti-friction coatings can be designed to meet specific applications. The coatings are permanently bonded to the metal surface and provide a lubricating film preventing direct metal to metal contact.


This compound is used on the threads of fasteners, It can prevent galling of mating surfaces. Anti-seize compounds are frequently used with stainless steel fasteners to prevent this effect. In some applications it is used to improve corrosion resistance to allow the parts to be subsequently dis-assembled, it can provide a barrier to water penetration since the threads are sealed by the compound. Anti-Seize products provide protection in harsh environments and extreme temperatures, they prevent fretting and galvanic corrosion and can also be used as running-in lubricant for new equipment.


Dimensional standards for fasteners, developed by the American Society of Mechanical Engineers. (ASME)   


Austenite steel is tough, non-magnetic and tends to work-harden rapidly when cold worked in steels which are austenitic at ordinary temperatures. 



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