Glossary

The Hall–Héroult process is the main industrial method for producing pure aluminum metal from alumina (aluminum oxide, Al₂O₃), which is first refined from bauxite using the Bayer process. Developed independently in 1886 by Charles Martin Hall in the United States and Paul Héroult in France, this process transformed aluminum from a rare, costly laboratory curiosity into a mass-produced, everyday material.

At its core, the Hall–Héroult process is an electrolytic reduction system that uses electric current to separate aluminum from oxygen in molten alumina. Because alumina has a very high melting point of about 2,050°C, it is dissolved in molten cryolite (Na₃AlF₆), which lowers the operating temperature to roughly 950–1,000°C. The electrolytic cell—known as a reduction pot—is a carbon-lined steel container that serves as the cathode, while large carbon blocks suspended from above act as the anodes. Additives like aluminum fluoride (AlF₃) and calcium fluoride (CaF₂) are often used to enhance electrical conductivity and stability.

When alumina is introduced into the molten cryolite bath, it dissolves and separates into aluminum ions (Al³⁺) and oxide ions (O²⁻). As a powerful direct current passes through the cell, these ions migrate to their respective electrodes. At the cathode, aluminum ions gain electrons and are reduced to molten aluminum metal through the reaction Al³⁺ + 3e⁻ → Al (liquid). At the same time, at the carbon anode, the oxide ions lose electrons and react with carbon to form carbon dioxide gas, following the oxidation reaction C + O²⁻ → CO₂↑ + 4e⁻. These two reactions occur simultaneously, continuously producing aluminum while consuming the carbon anodes in the process.

The newly formed molten aluminum collects at the bottom of the cell because it is denser than the electrolyte, and it is periodically siphoned off and cast into ingots, billets, or other industrial forms. The carbon anodes gradually burn away as they react with oxygen to form CO₂, so they must be regularly replaced. Modern smelters typically use either prebaked carbon anodes or self-baking anodes, depending on the design of the reduction cells.

The Hall–Héroult process is extremely energy-intensive, requiring roughly 13–15 kilowatt-hours (kWh) of electricity per kilogram of aluminum produced, which is why aluminum smelters are often built near hydroelectric or geothermal power sources. The process operates continuously under carefully controlled voltage, temperature, and composition to maintain purity and efficiency.

Hammer drive anchors are versatile fasteners used in various building materials such as concrete, brick, mortar, and cement blocks. This fastener consists of a slotted, cylindrical body with a nail protruding through its center; these anchors are installed by inserting the fastener into a pre-drilled hole and then driving the nail down with a hammer. The expanding sleeve grips the surrounding material tightly, providing a reliable and strong attachment point for fixtures, brackets, or other items in a wide range of applications.

A hanger bolt is a dual-ended fastener with wood screw threads on one end and machine screw threads on the other, designed to attach objects to wood while providing a machine-threaded stud for connecting other components such as metal brackets, electrical fixtures, or equipment mounts. It’s a hybrid fastener that bridges wood structures and mechanical assemblies.

The wood-threaded end (often coarse and tapered) is designed to be screwed directly into wood, composite material, or a wooden frame. It typically has a pointed tip and deep threads for a secure grip. The machine-threaded end (fine and uniform) is meant to accept a nut, washer, or tapped metal fitting, allowing for removable or adjustable connections.

Hanger bolts are commonly used in furniture assembly, building construction, electrical installations, and HVAC systems. For example, they are often used to mount legs to tables, hang pipes or ceiling fixtures from wooden joists, or attach heavy objects to wooden beams.

Installation usually requires pre-drilling a pilot hole into the wood, then driving the wood-threaded portion into place using a double nut technique (two nuts locked together on the machine end) or a special hanger bolt driver that fits into a drill or wrench.

Hanger bolts are typically made from carbon steel, stainless steel, or zinc-plated steel, offering strength and corrosion resistance for both indoor and outdoor use.

A beveled washer is a washer designed with a sloped or wedge-like shape rather than a flat surface. Its purpose is to correct for angled or irregular bearing surfaces in bolted joints, ensuring that the nut or bolt head seats evenly. By creating a proper fit between the fastener and the surface, beveled washers help distribute loads more evenly and prevent damage caused by misalignment.

The washer is typically thicker on one side and tapers to a thinner edge on the other, which allows it to compensate for sloped surfaces such as the flanges of I-beams or channels. Without a beveled washer, a bolt tightened against an angled surface would not sit squarely, causing bending stresses in the fastener and reducing the strength and reliability of the connection.

Beveled washers are usually made from hardened steel to handle heavy structural loads, though stainless steel and other alloys are available for applications requiring corrosion resistance. Their design not only helps align fasteners correctly but also improves safety by maintaining proper load distribution and reducing the risk of bolt loosening or shear failure.

They are most commonly used in structural steelwork, particularly in buildings, bridges, and heavy equipment where angled flanges are common. Beveled washers are also applied in machinery, automotive, and railway assemblies, or in any situation where fasteners are installed on surfaces that are not parallel. Their wedge-shaped design makes them essential in ensuring durability and reliability in critical load-bearing applications.

A hardened flat washer is a type of flat washer that has been heat-treated or hardened to increase its strength and durability. These washers are used to distribute the load of a fastener (such as a bolt or nut) more evenly over a surface and are designed for use in applications where high levels of stress, load, or wear are expected.

Plow Bolt Washers are through hardened for Grade 8 or better applications — preventing imbedding or distortion to the washer and material being clamped. The washers provide a smooth, level protective bearing surface to tighten nuts and bolts. For added strength, Plow Bolt Washers are thicker than standard USS washers for more demanding heavy-duty applications (plows). Earnest offers the washer in a corresponding Grade 8 or better strength.

The measure of a material’s resistance to deformation, scratching, or indentation. In fasteners, hardness level indicates how durable the surface is and how well it can resist wear and damage over time. It’s usually shown as a number based on standardized tests like the Rockwell, Brinell, or Vickers scales.

The Head Ductility Block Test is a mechanical test used to evaluate the ductility and toughness of a nail’s head, ensuring it can withstand deformation without cracking or breaking. This test focuses specifically on the head portion of the nail, since nail heads often endure repeated hammer impacts during installation and must resist splitting or flaking.

In the test, the nail is driven into or against a ductility block, which is usually a hardened steel or standardized block fixture. As the nail is struck, the head deforms under controlled loading conditions. The nail is then examined to see whether the head remains intact, develops cracks, or separates from the shank. The degree of deformation the head can undergo before failure indicates its ductility.

The purpose of the Head Ductility Block Test is to ensure that nails have sufficient malleability to handle installation forces without losing structural integrity. A brittle head might crack or shear off, which could compromise fastening strength and safety.

This test is often used in nail manufacturing quality control to verify material properties, heat treatment processes, and overall performance standards. It helps ensure nails meet industry requirements for durability in real-world applications such as construction, carpentry, and structural fastening.

Heat treating a fastener is the process of heating and cooling it under controlled conditions to alter its internal structure and improve performance. By doing this, manufacturers can increase hardness, tensile strength, toughness, and resistance to wear or fatigue, ensuring the fastener can handle demanding applications without premature failure.

Depending on the requirements, heat treatment may involve hardening and quenching to maximize strength, tempering to reduce brittleness, annealing to improve ductility, or case hardening methods to create a tough core with a hardened surface. These treatments are essential for structural bolts, aerospace fasteners, and other critical applications where durability and reliability are non-negotiable.

Earnest Machine Products line of B7 Heavy Hex Cap Screws are manufactured to the material and physical properties specified by the American Society for Testing and Materials standard ASTM A193 for Grade B7. The overall dimensions are made to the requirements of ASME B18.2.1 for heavy hex cap screws.

Otherwise known as Heavy or Heavy Thin Nuts, Heavy Hex Jam Nuts are half as small as Hex Nuts. They resemble Hex Jam Nuts; however, they’re larger across the flats. These nuts are generally used to bolt light poles and electrical lines. Earnest carries a full line of Heavy Hex Jam Nuts in Grades 2, 5, 8, and A194 2H.

Heavy Hex Nuts, or Structural Nuts, hold the world together — in charge of securing together buildings, bridges, and warehouses. Their job is to bolt I-beams to one another in order to raise structures. Heavy Hex Bolts provide a greater width across the flat compared to Finished Hex Bolts for a dispersed clamping load. Earnest offers Grades 5 and C, also available in lefty threads.

An industrial heavy hex slotted nut is a specialized type of nut designed for high-strength fastening in heavy-duty applications. It combines the characteristics of a heavy hex nut and a slotted nut (also known as a castle nut). These nuts are used in situations where a secure and locked fastening is critical, often in conjunction with a cotter pin or locking wire.

Heavy Square Nuts, like their smaller counterpart Square Nuts, are widely used in the locomotive industry. They are designed to have a larger square — increasing the bearing surface size. Earnest provides these classic-looking nuts in Grades 2 and 5 for durability and ductility.

A helical screw insert, also known as a helicoil (a brand name), is a threaded wire coil used to repair or reinforce tapped holes in metal, plastic, or composite materials. It creates strong internal threads for bolts or screws, especially in softer materials like aluminum or magnesium.

Heavy Helical Spring Washers, or Heavy Helical Spring Lock Washers, are designed to prevent loosening in vibrating applications. The circular coil grabs onto the head and material being fastened, creating a locking action. Heavy Helical Spring Washers are through hardened with a large width to improve strength and performance. Heavy lock washers are for use in Grade 8 or better applications.

Light Helical Spring Washers, or Light Helical Spring Lock Washers, are designed to prevent loosening in vibrating applications. The circular coil grabs onto the head and material being fastened, creating a locking action.

A Helical Spring Regular Lockwasher, commonly known as a split lock washer, is a type of washer used to prevent fasteners like bolts or screws from loosening due to vibration, movement, or torque. The washer is designed with a helical (spiral) shape that provides a spring action when compressed. This spring action helps maintain tension on the fastener, locking it in place.

A Helicoil® insert is a type of wire thread insert used to create strong, durable threads inside softer or damaged materials. It’s essentially a tightly wound stainless-steel wire coil, shaped into a helical spring, that’s screwed into a tapped hole to provide internal threads.

Instead of cutting threads directly into aluminum, magnesium, plastic, or other weaker materials—where bolts could strip out—a Helicoil® insert reinforces the hole with hardened steel threads. It not only repairs stripped threads but also increases load-carrying capacity and wear resistance. The insert’s diamond-shaped cross-section allows standard bolts or screws to fit perfectly once installed.

Common in aerospace, automotive, electronics, and machinery industries—anywhere lightweight materials need strong, reliable fastener joints. They’re also widely used in repair and maintenance, restoring stripped or worn threads to “better-than-new” strength.

Hematite is a naturally occurring iron oxide mineral with the chemical formula Fe₂O₃, and it is one of the primary ores of iron used in steelmaking. It contains about 70% iron by weight, making it one of the richest and most important sources of iron on Earth.

Hematite forms in both metallic and earthy varieties, depending on how it crystallizes. In its pure, crystalline form, it appears as a dark steel-gray or black mineral with a metallic luster, often showing a slight red tint on its edges. In its more common earthy form, it appears as a reddish-brown, dull powdery material—this variety is sometimes called red ochre and has been used as a pigment since prehistoric times. Regardless of appearance, hematite always leaves a reddish-brown streak when scratched on a surface, which is one of its most distinctive identifying features.

Hematite forms under a wide range of geological conditions. It can develop through precipitation from water, oxidation of other iron minerals (like magnetite), or as a weathering product of iron-rich rocks. It is commonly found in sedimentary deposits, banded iron formations, and metamorphic and igneous environments. Major hematite deposits are found in Brazil, Australia, China, India, Russia, and the United States—notably in the Lake Superior region, which has supplied iron ore for over a century.

In industrial use, hematite is primarily mined, crushed, and smelted in a blast furnace, where it is reduced by carbon (in the form of coke) to produce pig iron, which is then refined into steel. The reaction removes oxygen from the Fe₂O₃ molecule, leaving behind metallic iron.

Beyond metallurgy, hematite has several secondary uses. Finely ground hematite is used as a pigment for paints and cosmetics due to its rich red color. It is also used as a radiation shielding material, in heavy concrete, and as a polishing compound. Because of its magnetic properties when heated, it has also found uses in scientific instruments and electronics.

A hex bolt is a type of fastener with a hexagonal (six-sided) head and a partially or fully threaded shaft. It is designed to be used with a nut or tapped hole and tightened using a wrench or socket.

Castle Nuts, or Slotted Nuts, resemble Hex Slotted Nuts; however, the tops of the their corners are machined off for better cotter pin fitting. The design prevents the nuts from loosening in rotating applications such as bearings and bushings. Earnest offers the nuts in Grades 2 and 5.

A hex castle nut DIN 935 is a type of fastener designed to be used in applications where a secure, locking connection is needed, typically with a cotter pin or wire. The DIN 935 standard refers to a specific German (Deutsches Institut für Normung) specification for castle nuts, ensuring uniform dimensions and manufacturing standards.

Coil Nuts, or Hex Coil Nuts, are used with Coil Thread Hex Bolts and rods for quick assembly and disassembly of concrete forms. With their special wide design and rounded root coil, the nuts are self-cleaning. Coil Nuts are used in the construction industry to help build concrete sidewalks, roads, and buildings.

Hex Coupling Nuts are made from carbon steel and are designed for use with threaded rod studs. These fully threaded Hex Coupling Nuts are used to attach two lengths of rods together to form a long, secure thread length.

A Hex Flange Bolt DIN 6921 is a hexagonal-head bolt with an integrated circular flange at the base of the head. The flange acts like a built-in washer, distributing the clamping load over a wider area and helping to prevent damage to the connected surfaces. This design also provides greater holding power and resistance to loosening from vibration compared to a standard hex bolt and separate washer setup.

The DIN 6921 specification comes from the German Institute for Standardization (Deutsches Institut für Normung) and defines precise dimensions, tolerances, and material requirements for this bolt type. Under the DIN 6921 standard, the flange is flat and smooth — it’s not serrated. However, many manufacturers produce serrated flange bolts as a variation for applications requiring better vibration resistance.

Key features:

- Head shape: Hexagonal for use with standard wrenches or sockets.

- Flange: Smooth circular base under the head that acts as a washer.

- Thread: Fully or partially threaded, depending on length and application.

- Materials: Usually made from carbon steel, alloy steel, or stainless steel (A2, A4).

- Finishes: Common coatings include zinc-plated, hot-dip galvanized, black oxide, or plain steel.

Applications:
Hex Flange Bolts DIN 6921 are widely used in automotive, machinery, structural, and heavy equipment assemblies — anywhere vibration resistance, efficient load distribution, and reliable clamping are critical.

Earnest’s Flange Bolts are made to Property Class 10.9 standard to provide the durability and strength.

Commonly used to secure components to truck frames, Hex Flange Screws offer a built-in flange that distributes the clamping load over a wider area, eliminating the need for a separate washer. Earnest Machine stocks a large selection of high-strength, inch, metric, and JIS hex flange screws ready-to-ship the same day.

A hex lag screw, also known as a lag bolt, is a large, heavy-duty screw with a hexagonal head, designed for securing heavy materials such as wood, metal, or masonry. Unlike traditional screws, lag screws require pre-drilled holes and are commonly used in construction, woodworking, and outdoor projects where strong, durable fastening is necessary.

Hex Serrated Flange Screws offer a locking head design with built-in serrations on the bearing face of the flange. These serrations allow the screw to lock onto its installation surface providing excellent resistance to loosening due to vibration. Earnest Machine offers Hex Serrated Flange Screws in both standard and large flange diameter styles.

A Hex Flange Nut is a six-sided nut with a wide, washer-like base that extends from one side. This built-in flange acts as an integrated washer, spreading the clamping load of the nut over a larger surface area. The design helps prevent damage to the connected part, reduces the risk of loosening under vibration, and eliminates the need for a separate washer during assembly.

The flange can have two primary styles:

- A smooth (plain) flange, which provides even load distribution and prevents surface damage.

- A serrated flange, where small radial teeth on the underside bite into the mating surface to resist loosening and rotation, especially in applications subject to vibration.

Hex flange nuts are most commonly used in automotive, machinery, and heavy equipment applications, where strong, vibration-resistant fastening is required. They are typically made from carbon steel, stainless steel, or alloy steel, and are often coated with zinc, black oxide, or galvanization for corrosion protection.

A Hex Flange Nut DIN 6923 is a type of hexagonal nut that includes a built-in washer-like flange at its base. This flange serves to distribute the clamping load over a larger surface area, reducing the risk of damage to the part being fastened and improving the nut’s ability to resist loosening due to vibration.

The DIN 6923 designation refers to a specific German (Deutsches Institut für Normung) standard that defines the nut’s dimensions, tolerances, material grades, and mechanical properties. According to this standard, the nut’s flange is typically serrated or smooth:

- Serrated flange nuts have radial teeth on the flange’s underside that grip the mating surface, helping to prevent the nut from backing off under vibration.

- Smooth flange nuts distribute the load more evenly but do not have the same locking ability as serrated types.

These nuts are widely used in automotive, machinery, and industrial applications because they simplify assembly (no need for a separate washer) and maintain tightness even in dynamic environments.

Materials and Finishes:
Hex flange nuts DIN 6923 are typically made from carbon steel, stainless steel (A2, A4), or alloy steel, and often come zinc-plated, galvanized, or black-oxide coated for corrosion resistance.

Commonly used to secure components to truck frames, Hex Flange Screws offer a built-in flange that distributes the clamping load over a wider area, eliminating the need for a separate washer. Earnest Machine stocks a large selection of high-strength, inch, metric, and JIS hex flange screws ready-to-ship the same day.

AKA: Frame Bolt

Hex Head Bolts are standard bolts. They have a wide variety of applications for maintenance and repair workers. A correct shoulder length will provide added strength compared to a fully threaded bolt, however, restricting its versatility. Earnest’s unique line of Hex Head Bolts are offered in hard-to-find sizes in Grades A, 5, and 8 (BD) to ensure the proper strength in every application.

A hex head cap screw is a precision-threaded fastener with a six-sided (hexagonal) head designed to be tightened with a wrench or socket. It’s one of the most common and versatile fasteners used in machinery, construction, and equipment assembly, known for providing a strong, precise, and reliable clamping force.

Unlike ordinary hex bolts, hex head cap screws are manufactured to tighter tolerances and often feature a machined washer face under the head and chamfered threads at the tip. These design details allow for more accurate torque control and even load distribution when the screw is tightened, making them suitable for critical or precision applications.

Hex head cap screws can be either fully threaded (threads running the entire length of the shank) or partially threaded (with a smooth shoulder section under the head), depending on whether the joint requires shear strength or maximum thread engagement.

They are typically made from carbon steel, alloy steel, or stainless steel, and can be heat-treated for high strength. Common finishes include zinc plating, black oxide, or galvanization for corrosion protection. Standard specifications include ANSI B18.2.1, ISO 4014/4017, and DIN 933/931, depending on the regional manufacturing standard.

Earnest Machine stocks this style of fastener in diameters ranging from 1/4” to 3” with lengths ranging from 1/2” to 20” with a wide selection of grades and finishes to choose from.

A Hex Head Cap Screw DIN 931 is a type of fastener that is partially threaded, featuring a hexagonal (six-sided) head, and conforms to the DIN 931 standard, which specifies the dimensions and requirements for metric hex head cap screws. These screws are used to secure two or more components together in mechanical and structural applications.

A Hex Head Cap Screw DIN 933 is a type of fully threaded fastener with a hexagonal head, conforming to the DIN 933 standard. This standard specifies the dimensions and mechanical properties for these screws, ensuring consistency and reliability in various applications.

Used in the construction industry, Concrete Form Bolts, or Form Bolts, help build concrete walls, sidewalks, roads, and buildings. Their special thread design allows the ability to assemble and disassemble concrete forms with ease. The “coil” thread, a special wide thread with a rounded root form, is designed to be self-cleaning while it’s unthreaded — good for multiple uses.

Saddle Bolts, Suspension Bolts, Suspension Saddle Bolts, or Truck Suspension Bolts all describe the bolts used for truck suspensions. Commonly used in Mack trucks, these bolts are used in truck suspension assemblies. Earnest carries a Grade 8 for added toughness to withstand heavy loads.

Earnest's line of structural fasteners are manufactured to the requirements of ASTM for use in the construction and remodeling of buildings, warehousing wind turbine towers and general construction. Heavy hex structural bolts are designed to ensure the clamp loads developed in the assembly are distributed over a larger area than a standard hex heads. They also provide a larger wrenching area to resist rounding off of the head.

The Hex Tap Bolts are standard bolts that are fully threaded. They have a wide variety of applications and are versatile for maintenance and repair workers. The term “Tap Bolt” refers to a Hex Head Bolt that is threaded to the head. The added thread guarantees a fit to a variety of grip ranges for any job. Earnest’s line of Hex Tap Bolts is found in Grade 5 and 8 to ensure the proper strength in every application.

When you are looking for nuts that will provide a better wrench ability and prevent slippage, Hex Hi Nuts will get the job done. With a taller hexagonal face (twice as tall as Hex Nuts), it gives more surface to wrench in hard-to-reach socketed situations. These nuts can be found fastening a variety of applications, including suspensions in trucks and construction vehicles.

A hex jam nut is a thin, low-profile nut with a hexagonal (six-sided) shape. It is designed to be used in combination with another standard nut to "jam" the threads and prevent both nuts from loosening under vibration or load. Jam nuts are often used in applications where space is limited, and a thinner nut is needed.

Hex Large Flange Nuts (No Serrations) are specialized hex nuts that feature a large, flat, circular base (flange) on one side, but without the serrations typically found on other flange nuts. This design provides a greater surface area for distributing pressure and securing materials, without the additional locking function that serrations provide.

A hex machine screw nut is a type of hexagonal (six-sided) nut specifically designed to be used with machine screws. Machine screws are small-diameter screws with fine threading, typically used for precision fastening in light to medium-duty applications. The hex machine screw nut has internal threads that match the threads on a machine screw, allowing the two to be fastened securely together.

Hex Nuts are the most common nuts on the market. For metric sizes, the two most common dimensional standards that metric hex nuts are made to are either DIN 934 or ISO 4032. These two standards will have different tolerances on the thickness and the width across the flats (especially for the M10, M12 and M14 sizes). Functionally these nuts are interchangeable when the same property class is used. Earnest offers hex nuts made to DIN 934 in metric Classes 8 and 10.

Hex Nuts are the most common nuts on the market. Metric hex nuts made to ISO 4032 and DIN 970 have the same tolerance range on the width across flats (wrench size) and thickness. For metric nuts, the two most common dimensional standard referenced are per ISO 4032/DIN 970 or DIN 934. These two standards will have different tolerances on the thickness and the width across the flats (especially for the M10, M12 and M14 sizes). Functionally these nuts are interchangeable when the same property class is used. Earnest offers hex nuts made to ISO 4032/DIN 970 in metric Classes 8 and 10.

A hex serrated flange lock nut is a type of self-locking nut designed to resist loosening caused by vibration, torque, or movement. It combines three key features — a hexagonal shape, a flanged base, and serrations (teeth-like ridges) on the underside of the flange — to provide superior grip and load distribution compared to standard nuts.

The hex shape allows for easy tightening with standard wrenches or sockets, while the flange acts as a built-in washer, spreading the clamping load over a larger surface area and protecting the material beneath from damage. The serrations bite into the mating surface when the nut is tightened, creating friction that prevents the nut from backing off due to vibration or dynamic loads.

These nuts are commonly made from hardened steel, stainless steel, or zinc-plated materials for strength and corrosion resistance. They are frequently used in automotive assemblies, heavy machinery, and industrial equipment where fasteners are exposed to continuous vibration or movement.

In essence, a hex serrated flange lock nut combines secure fastening, even load distribution, and vibration resistance into one compact and efficient design, eliminating the need for a separate washer or locking device.

A Hex Serrated Flange Locking Machine Screw is a specialized type of fastener designed for mechanical applications where a secure, vibration-resistant connection is needed. It combines a hexagonal head for easy installation, a built-in flange for load distribution, and serrations underneath the flange that act as a locking mechanism.

A Hex Serrated Flange Locking Machine Screw (Stainless) is a specialized fastener designed to provide a secure, vibration-resistant connection, commonly made from stainless steel for enhanced corrosion resistance. This type of screw combines a hexagonal head, a serrated flange, and machine screw threads, making it ideal for use in various mechanical, automotive, and industrial applications.

A hex serrated flange nut is a specialized type of hex nut that has an integrated flange at the base, with serrations on the flange surface. The flange acts like a built-in washer to spread the load over a larger area, while the serrations provide a locking mechanism that prevents loosening under vibration.

A hex socket shoulder screw, also known as a shoulder bolt or stripper bolt, is a type of precision fastener characterized by three main parts: a hex socket drive, a cylindrical shoulder, and a threaded end. The hex socket allows the screw to be tightened or loosened using an Allen wrench (hex key), while the shoulder—a smooth, unthreaded section with a larger diameter than the threads—acts as a bearing surface or spacer between components.

These screws are designed for applications that require precise alignment and smooth movement between parts, such as in machinery, tooling, die assemblies, and pulleys. The shoulder provides a durable surface for rotation or sliding, while the threaded portion holds the assembly securely in place.

Typically made from hardened alloy or stainless steel, hex socket shoulder screws are known for their strength, wear resistance, and precision tolerances. They are commonly used in mechanical linkages, mold components, moving parts, and jigs, where accurate spacing and motion control are critical.

A hex thick nut is a heavy-duty hexagonal nut with a greater thickness (height) than a standard hex nut. The increased thickness provides more thread engagement, higher strength, and better resistance to loosening under vibration or heavy load conditions.

These nuts are commonly used in structural, machinery, and heavy-equipment applications where a stronger and more secure fastening is required. Because of their larger size, they can handle greater torque and distribute the clamping force over a wider area, reducing the risk of thread stripping or fastener failure.

Hex thick nuts are usually made from carbon steel, alloy steel, or stainless steel, and they often comply with standards such as DIN 6330 or ASTM A563 (Grade C or DH) for structural use. They may also be coated (zinc, black oxide, or hot-dip galvanized) for corrosion resistance.

A hex thread adapter is a type of fitting or connector designed to join two components with different thread sizes, types, or genders, while providing a hexagonal body that allows tightening with a wrench or socket. These adapters are commonly used in plumbing, hydraulic, pneumatic, and mechanical assemblies where threaded connections need to transition smoothly and securely between dissimilar parts.

The hexagonal body serves two key purposes — it provides a flat surface for gripping during installation and ensures torque can be evenly applied without damaging the threads. The adapter itself typically has male threads on one end and female threads on the other, or two different male thread types (e.g., NPT to BSPT, or metric to UNF), depending on the application.

Hex thread adapters are usually made from brass, stainless steel, carbon steel, or aluminum, depending on factors like pressure, temperature, and corrosion resistance requirements. For instance, stainless steel versions are used in corrosive or sanitary environments, while brass is preferred for air and fluid systems.

In practical terms, these adapters allow engineers and technicians to connect incompatible threaded components, modify plumbing or fluid lines, or make quick conversions between metric and imperial thread systems.

A hex wheel nut is a type of fastener specifically designed to secure a vehicle’s wheel to its hub or axle assembly. It has a six-sided (hexagonal) exterior that allows it to be tightened or loosened using a standard wrench or socket. The internal threads of the nut engage with the wheel stud threads to clamp the wheel firmly against the hub, ensuring stability and safe operation while driving.

These nuts are typically made from high-strength steel and are often zinc-plated, chrome-plated, or coated to resist corrosion and withstand the high stresses of vehicle movement, braking, and vibration. The hex shape provides excellent grip for torque application, allowing precise tightening to manufacturer-specified torque values, which is critical for maintaining wheel alignment and preventing loosening.

Hex wheel nuts come in several variations — including open-ended, closed (acorn or cap) style, flanged, and locking (security) nuts — depending on the application and wheel design. They are most commonly used on cars, trucks, trailers, and heavy equipment, serving as one of the most essential fasteners in automotive safety and performance.

A chemical treatment applied to zinc or cadmium-plated fasteners to improve corrosion resistance. This finish forms a protective layer that helps prevent white rust and slows corrosion near small scratches or around areas of minor damage. Hexavalent chromate coatings are effective but have environmental and health concerns, which is why alternatives like trivalent chromate are becoming more common.

Hexavalent chromium (Cr⁶⁺) is a toxic, high-oxidation state of the element chromium. It is commonly found in industrial processes, coatings, and chemical compounds. Unlike trivalent chromium (Cr³⁺), which is an essential nutrient in small amounts, hexavalent chromium is hazardous to human health and the environment.

In industrial applications, hexavalent chromium compounds are used for electroplating, stainless steel production, corrosion-resistant coatings, pigments, dyes, and wood preservatives. Its strong oxidative properties make it highly effective for creating durable and protective finishes on metals, which is why it has historically been widely used in fastener coatings and plating.

Health and safety concerns are significant with hexavalent chromium. It is recognized as a carcinogen, capable of causing lung cancer, respiratory problems, and skin irritation upon prolonged exposure. Inhalation of hexavalent chromium particles is especially dangerous, and strict occupational safety regulations limit worker exposure. Many industries have moved toward safer alternatives, such as trivalent chromium coatings or non-chromium-based finishes, to reduce risks.

Environmental regulations, including those from OSHA, EPA, and the European Union’s RoHS and REACH directives, have heavily restricted the use of hexavalent chromium in recent years. Despite its effectiveness as a corrosion inhibitor, the toxic nature of Cr⁶⁺ has made the transition to safer coatings a priority for manufacturers, particularly in fastener production and surface finishing.

A Hi-Lok® fastener is a type of precision aerospace fastener designed to provide the strength of a bolt with the speed and consistency of a rivet. It’s a two-piece system made up of a threaded pin (similar to a bolt) and a collar (similar to a nut), which locks in place when installed.

Unlike standard bolts and nuts, a Hi-Lok® is installed using simple hand tools—no torque wrench is needed. The collar has a built-in torque control feature: once the correct preload is reached, the drive portion of the collar shears off, leaving a smooth, flush finish. This ensures every fastener is tightened to exactly the right clamp load, eliminating human error from over- or under-tightening.

Hi-Lok® fasteners are widely used in aerospace, defense, and high-performance industries where strong, lightweight, vibration-resistant joints are critical. They’re common in aircraft wings, fuselages, and engine assemblies, providing consistent structural integrity while being easier and faster to install than traditional bolted assemblies

Honing is a precision finishing process used to improve the surface quality, geometry, and dimensional accuracy of a workpiece. It involves using an abrasive tool, called a hone, which consists of bonded abrasive sticks mounted in a holder. The hone is rotated and moved back and forth under controlled pressure against the surface of the part, typically the inside of a cylindrical bore. The abrasive action removes a very small amount of material in a slow, controlled manner, creating a highly accurate, smooth, and often crosshatched surface finish.

Unlike grinding, which removes material more aggressively, honing is primarily about refinement and correction. It can correct imperfections such as slight out-of-roundness, taper, waviness, or surface irregularities left from earlier machining processes. The distinctive crosshatch pattern created during honing is especially important in applications like engine cylinders, where it helps retain lubrication, reduces friction, and extends the service life of the part.

Honing is commonly used in the production of automotive components (engine blocks, gears, hydraulic cylinders), aerospace parts, and precision machinery. It ensures parts meet tight tolerances, with high levels of surface smoothness and dimensional accuracy. Because it improves both geometry (straightness, roundness) and surface finish, honing is considered a finishing process for parts that demand the highest reliability and performance.

Hook Bolts, J-Bolts, or Bent Bolts have two designs used in rock quarries and mines. The J-Bolt Special Bend, otherwise known as Hook Bolt or Shaker Screen Bolt, supports angled ironed shaker screen frames. Resembling a checkmark, the bolt is heat treated to a Rockwell hardness of 25/34 to improve resistance to bending. The other design, the J-Bolt Round Bend, has a rounded radius hook to support tubular shaker screen frames. These bolts shift through dirt and heavy rock — a true testament to their strength.

Hot Dip Galvanized is a corrosion-resistant finish created by immersing a steel fastener into a bath of molten zinc. This process forms a thick, durable zinc coating that bonds to the steel surface, providing long-term protection, especially in outdoor or harsh environments.

Appearance - Fasteners with a Hot Dip Galvanized finish have a dull gray or matte silver appearance with a rough or uneven texture. The finish is noticeably thicker than other zinc coatings and may affect thread fit.

A manufacturing process that shapes metal into fasteners at elevated temperatures, specifically above the material's recrystallization point. Heating the metal makes it significantly more ductile and easier to form, requiring less force than cold forming. Hot forming is typically for larger-diameter fasteners, complex shapes, or materials that are difficult to work with at room temperature. Parts produced through this method may require an additional heat treatment to achieve the desired strength level.

A Huck bolt is a type of permanent, high-strength, vibration-resistant fastener used in heavy-duty applications where traditional bolts or rivets may loosen over time. Huck bolts are part of a category known as lockbolts, and they are widely used in industries such as railroad, aerospace, construction, and heavy equipment manufacturing.

A critical phenomenon where certain metals, especially high-strength steels used in fasteners, lose their ductility and become brittle due to the absorption of atomic hydrogen. This hydrogen can be introduced during manufacturing processes such as electroplating or acid pickling, or from environmental exposure like corrosion. The absorbed hydrogen migrates within the material, accumulating at stress points and internal defects. Under sustained or residual stress, this leads to the sudden, often delayed, and frequently catastrophic fracture of the fastener, even at loads well below its design strength. Post-plating baking is a common mitigation strategy to reduce this risk.

Article: How to Avoid Hydrogen Embrittlement for Zinc Plated Fasteners