Glossary

Machine bolts are used to fasten wood to wood, wood to metal, and metal to metal. They are typically installed into pre-drilled and tapped holes and utilized in heavy-duty applications. Earnest Machine stocks Machine Bolts in grades 2, 5, and grade 8, providing options for applications requiring increased strength and durability. Earnest also offers Machine Bolts in various diameters, lengths, and finishes, including RoHS-compliant Zinc Clear Trivalent and hexavalent-free Zinc Yellow Trivalent.

A machine screw anchor is a type of fastener used to secure machine screws into masonry or other solid materials like concrete, brick, or stone, where a regular screw wouldn’t hold. It’s essentially a sleeve or plug that gets inserted into a pre-drilled hole in the material. When a machine screw is threaded into the anchor, it expands or grips the surrounding material, creating a strong, reliable mounting point.

Industrial machine screws are specialized fasteners used to secure components in machinery and equipment. They are designed for precise applications where reliable fastening is required, often involving the assembly of metal parts or the attachment of machine components. These screws come in a variety of sizes, materials, and head styles, making them versatile for different industrial needs.

A manufacturing process that removes material from a part to shape it into a specific design. In fastener production, machining is used to form precise dimensions, threads, or other features by cutting, drilling, turning, or milling the material with specialized equipment.

Magnetic Particle Testing (MT) is a non-destructive testing (NDT) technique designed to detect surface and near-surface defects in ferromagnetic materials like iron, nickel, cobalt, and their alloys. The process begins by magnetizing the part either through direct current or by placing it in a magnetic field. When the material contains a discontinuity—such as a crack, seam, lap, or void—it interrupts the flow of the magnetic field. This disruption causes magnetic flux leakage at the defect site, which provides the basis for detection. Finely milled ferromagnetic particles, applied as either a dry powder or a suspension in liquid, are then spread across the surface. These particles are drawn toward the leakage fields and cluster along the defect, forming a visible indication of its presence.

This method is widely applied across industries like aerospace, automotive, construction, and energy, especially for inspecting welds, castings, and forgings. MT offers several advantages: it is highly effective for finding surface-breaking flaws and shallow subsurface defects, produces immediate and easily visible results, and is relatively quick and inexpensive to perform. However, it does have limitations—it only works on ferromagnetic materials, requires clean surfaces for accurate detection, and may miss deeper flaws that methods like ultrasonic or radiographic testing could identify. Despite these constraints, MT remains a practical, versatile, and widely used inspection tool for ensuring the integrity of critical components.

A family of engineered coating systems developed by Magni Industries, designed to protect fasteners and metal components against corrosion. Magni® coatings often combine an inorganic zinc-flake basecoat with an organic topcoat, offering customizable friction properties, color options, and high salt-spray resistance for automotive, construction, and heavy-equipment applications.

The major diameter of a thread is the largest diameter of a screw thread, measured from the crest of the threads on one side to the crest on the opposite side. If you picture the threaded portion of a bolt or screw as a cylinder with ridges cut into it, the major diameter is the diameter of the imaginary cylinder that touches the very tops of those ridges.

For an external thread (such as a bolt), the major diameter is the diameter across the outermost points of the external threads. For an internal thread (such as a nut), it is the diameter measured across the innermost points of the internal thread crests. Because it represents the overall size of the thread, the major diameter is typically the dimension used when identifying or naming a threaded fastener. For example, in an M10 × 1.5 metric bolt, “10 mm” refers to the major diameter.

The major diameter is important because it sets the nominal size of the fastener and influences whether two threaded parts will fit together properly. While the major diameter itself doesn’t carry most of the load—that happens along the flanks at the pitch diameter—it ensures clearance, proper engagement, and compatibility between mating threads.

Together with the minor diameter (measured at the roots of the threads) and the pitch diameter (the effective diameter where threads engage), the major diameter is one of the three critical dimensions that define the geometry and function of a thread.

Martensitic stainless steel is a category of stainless steel known for its high strength, hardness, and moderate corrosion resistance, achieved through heat treatment that transforms its crystal structure into martensite. It is characterized by a body-centered tetragonal (BCT) crystal structure, which forms when steel containing sufficient carbon is rapidly cooled or quenched from a high temperature. This gives martensitic stainless steels their distinctive ability to be hardened and tempered, much like carbon steels.

The composition of martensitic stainless steels typically includes 11.5% to 18% chromium and 0.1% to 1.2% carbon, with small amounts of other elements such as molybdenum, nickel, or vanadium to improve strength, corrosion resistance, and toughness. The chromium content provides the protective oxide layer that resists rust and oxidation, while the carbon allows for the formation of martensite during quenching, leading to significant hardness and wear resistance.

Unlike austenitic or ferritic stainless steels, martensitic grades are magnetic and can be heat treated to a wide range of hardness levels. However, this comes at a tradeoff: their corrosion resistance is generally lower, especially in environments involving chlorides or acids. They also tend to have reduced ductility and weldability compared to other stainless steel families.

Common martensitic grades include Type 410 (general-purpose, used for cutlery, valves, and turbine blades), Type 420 (high-carbon, used for surgical instruments and knives), and Type 440C (very high carbon, used for bearings, precision tools, and high-wear components). These steels are often used where mechanical strength, edge retention, and wear resistance are more critical than corrosion resistance.

In summary, martensitic stainless steels combine moderate corrosion resistance with exceptional hardness and strength, making them ideal for blades, tools, fasteners, shafts, and mechanical parts that require durability and resistance to wear. Their defining feature is that they can be hardened by heat treatment, which sets them apart from ferritic and austenitic stainless steels.

A material property describing resistance to surface deformation such as scratching, denting, or indentation. It is the underlying property that standardized tests quantify, while the resulting measurement or acceptable range is the hardness level.

Metallurgy is the branch of science and engineering that studies the properties, behavior, and processing of metals and their alloys. It involves understanding how the structure of metals—from the atomic level to the macroscopic scale—affects their performance, strength, and durability under different conditions.

The field of metallurgy can be divided into three main areas. Physical metallurgy focuses on how the internal structure of metals (such as grain size, crystal structure, and dislocations) influences their mechanical, electrical, and magnetic properties. Extractive metallurgy deals with the processes used to obtain metals from their ores, including smelting, refining, and electrolysis. Mechanical or industrial metallurgy applies this knowledge to the design, manufacturing, and treatment of metal products—covering processes like casting, forging, heat treatment, and welding.

Metallurgy plays a crucial role in nearly every industry that uses metals, including automotive, aerospace, construction, energy, and manufacturing. By understanding and controlling metallurgical processes, engineers can enhance metal performance, prevent failures such as corrosion or fatigue, and develop new materials with tailored properties for specific applications.

A system of measurement based on meters, centimeters, and grams, used internationally. In fasteners, “metric” refers to sizes and dimensions measured in millimeters.

A metric flat washer is a thin, round, flat piece of metal or plastic with a central hole that corresponds to a metric-sized fastener, such as a bolt or screw. It is used to distribute the load of the fastener more evenly across the surface of the material being fastened, preventing damage, reducing friction, and ensuring a more secure connection.

A metric hardened flat washer is a type of flat washer designed according to metric dimensions (millimeters) and made from hardened steel. The hardening process involves heat treatment to increase the washer's strength and durability, making it suitable for high-stress applications. These washers are used to distribute the load of a fastener, such as a bolt or screw, over a larger surface area, protect the material being fastened, and reduce wear.

A metric heavy hex nut is a type of fastener designed with a hexagonal (six-sided) shape, similar to standard hex nuts, but with a thicker and larger profile. These nuts are commonly used in applications where additional strength and durability are required, particularly in high-load or high-stress environments.

A metric hex head cap screw is a type of fastener that has a hexagonal (six-sided) head and a threaded shaft, designed to be used with metric-sized nuts or tapped (threaded) holes. The hex head allows for easy tightening and loosening using a wrench or socket. These screws are commonly used in machinery, automotive, construction, and structural applications, where precise, strong, and reliable fastening is required.

A Metric Hex Head Cap Screw (ANSI) is a type of threaded fastener with a hexagonal (six-sided) head, used for securing materials or components. It is manufactured to metric dimensions and follows specifications set by the American National Standards Institute (ANSI). These screws are widely used in machinery, construction, automotive, and many other applications.

Hex Jam Nuts are half the thickness of standard Hex Nuts and are commonly used in applications where a nut with a low-profile thickness is needed. This nut can also be used with a standard Hex Nut to create a locking action in your assembly. Earnest Machine stocks the largest selection of Hex Jam Nuts in industry, offering both inch and metric sizes with a variety of strength levels, thread directions, and finishes to choose from.

Otherwise known as Lug Nuts, Wheel Nuts are specifically designed to hold tire rims to an axle. These nuts are primarily used in automotive and construction equipment. In order to match the rim, the nuts are engineered to 60 degree, 90 degree, and radius faces.

A metric nylon insert hex flange lock nut is a specialized fastener that combines several important features: a hexagonal shape, a built-in flange, and a nylon insert to provide a secure, vibration-resistant fastening solution. This type of nut is commonly used in applications where both high torque and resistance to loosening are important.

A metric nylon insert hex flange lock nut is a specialized fastener that combines several important features: a hexagonal shape, a built-in flange, and a nylon insert to provide a secure, vibration-resistant fastening solution. This type of nut is commonly used in applications where both high torque and resistance to loosening are important.

A microscrew (miniature screw) is a very small machine screw used to fasten tiny components where space and weight are limited—think electronics, wearables, cameras, watches, and medical devices. In practice, people usually mean sizes ≤ M2 in metric (e.g., M1.6, M1.4, M1.2, M1.0, M0.8) or #0-80 and smaller in inch series (down to #0000-160). They’re made in common head styles (pan, flat, button, socket), drives (Phillips/JIS, Torx®, slotted), and materials like stainless steel, titanium, and brass, with finishes such as passivation or black oxide.

Because everything is tiny, installation uses low, precise torque (often measured in cN·m/N·cm), fine thread classes, and magnified/ESD-safe handling. Variants include thread-forming microscrews for plastics and micro set screws for collars/gears. The key idea: a standard screw in every way—just engineered for microscale assemblies with tight tolerances.

Microstructural inhomogeneities are small-scale irregularities or non-uniformities within the internal structure of a material, usually visible under a microscope. Instead of having a perfectly even composition and arrangement of grains, phases, or inclusions, the material contains localized variations that make certain regions behave differently under stress, temperature, or chemical exposure.

These inhomogeneities can take many forms. Common examples include non-metallic inclusions (like oxides or sulfides in steel), segregations of alloying elements during solidification, uneven grain sizes, voids, porosity, or differences in phase distribution (such as harder or softer regions in a heat-treated alloy). They may also include dislocations, twins, or other crystal defects.

While some microstructural variation is normal in engineered materials, significant inhomogeneities often act as weak points. They can disrupt the even flow of stress through the material, leading to stress concentrations that make crack initiation more likely. In fatigue, corrosion, and fracture mechanics, microstructural inhomogeneities are often the hidden initiators behind failure.

Controlling these features is a key part of materials engineering. Careful processing, refining, alloying, and heat treatment are all used to minimize unwanted inhomogeneities and produce consistent, predictable material performance. In advanced applications like aerospace, medical implants, or nuclear power, even tiny microstructural irregularities can be critical to long-term reliability.

A standard or specification developed by the U.S. Department of Defense that defines the performance, quality, and testing requirements of a product. Fasteners labeled “Mil-Spec” must meet strict requirements for material, strength, corrosion resistance, and uniformity, ensuring reliability in defense and aerospace applications.

A milling cutter is a rotating, multi-edge cutting tool used on milling machines and CNCs to remove material by shearing chips. Unlike a single-point lathe tool or a drill’s two lips, a milling cutter has many teeth that intermittently engage the work, so metal removal comes from the combined action of multiple edges as the tool feeds along a path.

Key anatomy features include the shank or arbor hole, which determines how the tool mounts—either a solid-shank cutter or a shell/face mill mounted on an arbor. The body carries flutes and teeth; the flutes form chip channels, while tooth geometry establishes rake, relief, and helix angle to control chip flow and cutting forces. Cutting diameter and length of cut set the practical step-over and depth capability. Edge style can be square, corner-radius, or ball nose; center-cutting end mills can plunge, whereas non-center-cutting designs cannot.

Common cutter types span end mills (square, ball, corner-radius) for profiling and pocketing, typically with 2–3 flutes for aluminum and 4–6 for steels; face mills or shell mills for planar surfacing using indexable inserts; and slab/plain, side-and-face, T-slot, Woodruff/keyseat, dovetail, and other form cutters that produce specific profiles. Additional families include chamfer and deburr mills, counterbores and countersinks, and thread mills that generate internal or external threads with CNC helical paths.

Cutter materials and coatings are chosen for the job. HSS and cobalt HSS are tough and forgiving but run at lower speeds. Solid carbide is stiff and wear-resistant for high-speed CNC work. Indexable platforms use carbide, ceramic, CBN, or PCD for larger diameters and hard or abrasive materials. Coatings—applied via PVD or CVD—such as TiN, TiCN, TiAlN/AlTiN, and DLC reduce wear and built-up edge; selection should match the work material and expected heat.

Choosing a cutter follows a straightforward logic. By material: aluminum favors high-helix 2–3-flute tools; steels run well with 4–6-flute AlTiN-coated carbide; stainless benefits from a tough grade, sharp edge, and lower helix; titanium and nickel alloys call for variable-pitch carbide and high rigidity. By operation and toolpath: facing suggests a face mill; deep pocketing and 3D work point to a ball or variable-helix end mill; keyways use keyseat cutters; threads benefit from thread milling for better control than tapping. Machine and toolholding matter—stiffer holders (heat-shrink, ER, whistle-notch) and minimal overhang reduce chatter. Chip control depends on flute count and helix for evacuation, and on whether to use coolant, MQL, or run dry, based on the material.

Practical use tips round it out. Prefer climb milling on CNC for better finish and tool life, reserving conventional milling for specific setups. Set feed per tooth (fz) and surface speed (Vc) from manufacturer data, and tune radial (ae) and axial (ap) engagement to avoid chatter. Monitor wear modes: built-up edge suggests raising speed or adding a suitable coating; chipping points to reducing runout or lightening radial engagement; and thermal cracking calls for avoiding intermittent coolant and reducing coolant cycling.

The minor diameter of a thread is the smallest diameter of a screw thread, measured from the root of the threads on one side to the root on the opposite side. If you imagine the thread profile as peaks (crests) and valleys (roots), the minor diameter corresponds to the imaginary cylinder that just touches the bottoms of all the thread grooves.

For an external thread (like on a bolt), the minor diameter is the diameter at the base of the external threads. For an internal thread (like in a nut), it is the diameter measured across the crests of the internal threads. In both cases, the minor diameter represents the narrowest point of the threaded section.

The minor diameter is important because it directly affects the strength of the fastener. Since this dimension determines the thickness of the metal left at the root of the thread, it defines how much shear area is available to resist stripping. A larger minor diameter means more material in the cross-section and generally higher strength, while a smaller one means the fastener may be weaker.

Along with the major diameter (measured across the crests of the threads) and the pitch diameter (the effective diameter where the threads of a nut and bolt actually contact each other), the minor diameter is one of the three key dimensions that define a thread’s geometry and ensure proper fit and load distribution.

The Mohs Hardness Scale is a comparative scale that measures the relative hardness of minerals and other materials based on their ability to resist scratching. It was developed in 1812 by German mineralogist Friedrich Mohs and is still widely used today as a quick, practical way to rank material hardness. The scale ranges from 1 to 10, with 1 being the softest and 10 the hardest. Each mineral on the scale can scratch any material ranked lower than itself, but not those higher.

At the soft end, talc is ranked at 1, meaning it can be easily scratched by any other mineral. At the hardest end, diamond is ranked at 10, representing the maximum hardness in natural materials. Other familiar examples include gypsum (2), calcite (3), fluorite (4), apatite (5), feldspar (6), quartz (7), topaz (8), and corundum (9, which includes sapphires and rubies).

The Mohs Scale is not linear but ordinal, meaning the difference in hardness between successive numbers is not equal. For example, diamond (10) is much harder compared to corundum (9) than corundum is compared to topaz (8). Despite this, the scale is practical for fieldwork and industry because it gives a fast and simple way to test hardness using scratch comparisons.

In the context of fasteners and industrial applications, the Mohs Hardness Scale is relevant for understanding wear resistance, abrasion resistance, and material compatibility. For example, coatings, cutting tools, and surface treatments are often selected based on hardness relative to the materials they will interact with. While engineers often use more precise hardness measures such as Rockwell, Vickers, or Brinell hardness tests, the Mohs scale remains a useful reference for comparing material durability in general terms.

The Morgan Impact Bend Angle Nail Test is a specialized mechanical test used to evaluate the toughness, ductility, and bend resistance of nails. It is designed to determine how well a nail can withstand impact and bending forces without cracking, breaking, or failing prematurely.

In the test, a nail is driven against or bent over a specified angle using a controlled impact load, often with a pendulum or hammer-like device. The nail is struck until it bends to a predetermined angle, and the degree of bending and the condition of the nail afterward (whether it bends smoothly, fractures, or shows signs of brittleness) are recorded.

The purpose of the Morgan test is to replicate the kinds of stresses a nail might face during real-world use — for example, when being hammered into tough materials or subjected to repeated impact in structural applications. A nail that passes the test demonstrates good impact resistance, bending capacity, and toughness, qualities important in construction, woodworking, and heavy-duty fastening.

This test is often cited in quality control and standardization for nail manufacturing, as it helps ensure that nails meet performance requirements for durability and safety.