Fastener Glossary

A fastener embedded in concrete or masonry to secure structural elements, machinery, or equipment to a foundation. Types include cast-in-place, adhesive, and mechanical expansion anchors.

American Society for Testing and Materials. An international standards organization that publishes technical standards for materials, products, systems, and services — including fastener grades like A307, A325, and A490.

ISO stainless steel grade equivalent to 304 stainless. Provides good general corrosion resistance. Suitable for most indoor and mild outdoor applications. Not recommended for chloride-rich or marine environments.

ISO stainless steel grade equivalent to 316 stainless. Contains molybdenum for enhanced resistance to pitting and corrosion in chloride environments. The preferred choice for marine and chemical processing applications.

A lubricant applied to fastener threads to prevent galling, seizing, and corrosion — particularly on stainless steel, aluminum, and high-temperature applications. Common types include copper, nickel, and moly-based anti-seize.

An externally threaded fastener designed to be inserted through holes in assembled parts and secured with a nut. Bolts do not cut their own thread — they require a mating thread or nut.

A bolt with a round, domed head and a square neck that grips into wood to prevent rotation during tightening. Commonly used in wood construction, decking, and fencing.

The compressive force created in a joint when a fastener is tightened. Maintaining proper clamp load is critical to joint integrity, especially under vibration or dynamic loads.

Unified National Coarse thread — the most widely used thread form in North America. Coarse threads are faster to assemble, more tolerant of damage, and less prone to cross-threading than fine threads.

A fastener designed to attach structures or equipment to concrete. Types include wedge anchors, sleeve anchors, drop-in anchors, adhesive anchors, and screw anchors.

The compressive force created in a joint by tightening a fastener. Proper clamping force ensures joint integrity, prevents relative movement, and maintains the preload throughout the life of the joint.

An internally threaded anchor installed flush with the concrete surface. A setting tool is used to expand the anchor. Accepts a threaded rod or bolt. Used for overhead and flush applications.

A process that deposits a thin metallic coating (commonly zinc, nickel, or chrome) on a fastener through electrolysis. Zinc electroplating is the most common coating for corrosion protection on hardware fasteners.

Unified National Fine thread — has more threads per inch than coarse thread. Provides greater preload for a given torque and better vibration resistance. Used in precision and automotive applications.

A bolt with a wide circular flange (washer) integrated beneath the head. The flange distributes clamping load over a larger area, eliminating the need for a separate washer.

The application of a protective zinc coating to steel or iron to prevent corrosion. Hot-dip galvanizing is the most durable method, immersing the part in molten zinc to create a thick, bonded coating.

A classification that defines the mechanical properties of a fastener, primarily tensile strength, yield strength, and proof load. Common North American grades: SAE Grade 2, 5, 8. Metric property classes: 4.6, 8.8, 10.9, 12.9.

An austenitic stainless steel alloy containing molybdenum, providing superior corrosion resistance to chlorides and seawater compared to 304. The standard specification for marine-grade fasteners.

A measure of a material's resistance to permanent surface deformation. Fastener hardness is often specified to ensure compatibility with mating materials and compliance with grade standards. Measured on scales such as Rockwell B or C.

A bolt with a six-sided (hexagonal) head. The most common bolt type in industrial and construction applications. Available in a wide range of grades, sizes, and coatings.

A galvanizing process in which steel is immersed in a bath of molten zinc at approximately 450°C, creating a thick, durable zinc-iron alloy coating. Provides superior corrosion protection compared to electroplating.

International Organization for Standardization. Publishes international standards for fasteners and hardware, including ISO metric thread standards (M series) and property class specifications.

A large wood screw with a hex head designed to fasten heavy structural wood members together or anchor hardware to wood. Driven with a wrench rather than a screwdriver.

A washer designed to prevent loosening of a fastener under vibration or torque. Types include split (helical spring), tooth (internal/external serrated), and Nord-Lock washer systems.

Thread form based on the ISO metric standard. Designated by 'M' followed by the nominal diameter in millimetres (e.g., M10 x 1.5). Metric fasteners use property class designations (8.8, 10.9, 12.9) rather than SAE grades.

Maintenance, Repair, and Operations. Refers to the category of supplies used for the maintenance and operation of industrial facilities and equipment — including fasteners, lubricants, abrasives, and tools.

An internally threaded fastener that mates with a bolt or threaded rod. Common types include hex nuts, nylon insert lock nuts (nylock), flange nuts, coupling nuts, and wing nuts.

A hex nut with a nylon insert in the top that grips the bolt thread to resist loosening from vibration. Suitable for temperatures below 120°C. One of the most widely used locking fasteners.

The distance between adjacent thread crests, measured in millimetres for metric threads or expressed as threads per inch (TPI) for imperial threads. Pitch determines whether a thread is coarse or fine.

The maximum tensile force a bolt can withstand without permanent deformation. Used as a quality assurance threshold. Typically 85–90% of the yield strength. Critical for bolted joint design.

The metric equivalent of SAE grade. A two-part designation where the first number represents 1/100 of the nominal tensile strength in MPa and the second indicates the ratio of yield to tensile strength. Examples: 8.8, 10.9, 12.9.

Society of Automotive Engineers. Publishes standards for fastener grades widely used in North America. SAE Grade 2, Grade 5, and Grade 8 are the most common bolt grades in general use.

A screw with a drill-point tip that can penetrate metal or other materials without a pre-drilled pilot hole. Commonly used in light steel construction, HVAC ductwork, and metal roofing. Also called Tek screws.

The maximum force a fastener can withstand in a direction perpendicular to its axis before fracturing. In structural connections, fasteners are often loaded in shear as well as tension.

A versatile concrete anchor with an expandable sleeve that spreads against the hole wall as the bolt is tightened. Suitable for concrete, block, and brick. Available in various head styles.

A precision fastener with a cylindrical head and a hexagonal socket drive. Allows high torque in tight spaces. Commonly made from alloy steel (Grade 12.9) with black oxide finish. Used in machinery and precision assemblies.

Fasteners made from corrosion-resistant steel alloys. The most common grades for fasteners are 18-8 (304) for general use and 316 for marine or highly corrosive environments. A2 and A4 are the ISO stainless property classes.

A high-strength bolt meeting ASTM A325 or A490 specifications, designed for use in structural steel connections. Must be installed with calibrated wrenches or turn-of-nut methods to achieve specified preload.

The maximum stress a fastener can withstand while being stretched before fracturing. Expressed in PSI (imperial) or MPa (metric). A key mechanical property used to define fastener grade.

The process of applying the correct preload to a bolted joint. Methods include torque wrenching, turn-of-nut, direct tension indicators (DTI), and hydraulic tensioners. Proper tensioning is critical in structural and pressure applications.

An anaerobic adhesive applied to threads to prevent loosening from vibration and to seal against leaks. Available in different strengths: low (removable), medium (standard), and high (permanent). Common brands include Loctite.

A fastener with continuous threads along its full length and no head. Used with nuts on both ends to join two threaded elements, as an anchor bolt, or as a structural tension member.

A rotational force applied to a fastener during tightening, measured in foot-pounds (ft-lb) or Newton-metres (Nm). Proper torque ensures the fastener achieves the required clamp load without yielding or breaking.

Unified National Coarse — a thread standard defined in the Unified Thread Standard (UTS). Coarse threads have fewer threads per inch than fine threads and are the default thread form for most bolts and screws in North America.

Unified National Fine — a thread standard with more threads per inch than UNC. Fine threads are used when greater precision, finer adjustment, or better vibration resistance is required.

A flat disc with a central hole placed under the head of a bolt or nut to distribute clamping load, prevent surface damage, or provide a smooth bearing surface. Types include flat, lock, fender, and spring washers.

A heavy-duty concrete anchor consisting of a threaded bolt with an expansion clip near the base. Expands against the concrete hole wall when the nut is tightened. The most common anchor for heavy structural loads in solid concrete.

The stress at which a fastener begins to deform permanently (plastic deformation). Fasteners should not be loaded beyond yield strength in service. A critical value in joint design and torque specification.

A high-performance corrosion protection system (e.g., Geomet, Dacromet) applying inorganic zinc flakes in a thin layer. Provides excellent salt spray resistance (often 1000+ hours) without hydrogen embrittlement risk.

A thin electrodeposited zinc coating applied to steel fasteners for corrosion protection. Standard for indoor or mild-environment applications. Not recommended for direct outdoor exposure without additional treatment.