Understand fastener types, threads, heads, drives, materials, and finishes. Find a definition, compare related terms, and explore matching product categories.
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Materials & finishes
A family of stainless steels containing approximately 18% chromium and 8% nickel. Common in general-purpose corrosion-resistant fasteners, 18-8 is a material description rather than a strength grade. Confirm the specified alloy and mechanical requirements when replacing an existing fastener.
Materials & finishes
A stainless steel containing molybdenum, which improves resistance to chloride-related corrosion compared with common 18-8 grades. Often considered for coastal and chemical exposure. It is not immune to corrosion; suitability still depends on the environment and application.
Materials & finishes
A magnetic stainless steel that can be hardened by heat treatment. Used in some tapping and drilling screws where hardness is important. It differs from common 18-8 and 316 stainless steels in both mechanical and corrosion behavior, so confirm the application requirements.
Materials & finishes
A lightweight metal used for fasteners, rivets, spacers, and other hardware. Alloy and temper influence strength and performance. Consider the surrounding metals and exposure when selecting aluminum, since dissimilar-metal contact can affect corrosion behavior.
Fastener types
A fastener used to secure a fixture to a base material such as concrete, masonry, or drywall. Expansion, screw, and hollow-wall anchors work differently. Select an anchor for the actual base material, fixture thickness, and required load.
Fastener types
A conical spring washer that deflects under compression. It can help maintain force in an assembly as components expand, contract, or settle. Its dimensions, material, and load-deflection characteristics determine how it performs.
Materials & finishes
A black conversion finish commonly applied to steel fasteners. It adds little thickness and is often combined with oil for limited corrosion protection. Specify the required protection rather than selecting black oxide solely for its appearance.
Fastener types
A rivet installed with access to only one side of the joint. A setting tool pulls a mandrel to expand the rivet body and clamp the materials together. Match the rivet diameter, grip range, and material to the joint.
Fastener types
An externally threaded fastener commonly passed through a clearance hole and tightened with a matching nut. Product names sometimes use bolt and screw interchangeably, so verify the actual dimensions, thread, material, and strength specification.
Materials & finishes
A copper-zinc alloy used for fasteners where appearance, corrosion behavior, or electrical properties are important. Brass differs from bronze and stainless steel. Verify the specified alloy and strength requirements rather than selecting a replacement by color alone.
Heads & drives
A screw head with a low rounded dome and a flat bearing surface underneath, commonly paired with an internal drive. It sits above the work surface. Head diameter, height, and strength requirements distinguish it from other socket screw styles.
Fastener types
A nut held in a spring-metal cage that clips into a compatible panel opening. Common in equipment racks and enclosures. Match the cage to the hole dimensions and panel thickness, and confirm the nut thread size.
Fastener types
A nut with a closed end that covers the exposed end of a mating thread. Domed versions are often called acorn nuts. Check available internal depth so the bolt does not bottom out before the nut clamps the joint.
Fastener types
A screw designed to remain attached to a panel or component when disengaged from its mating thread. Often used on removable covers to reduce loose hardware. Retention method, panel thickness, and available travel depend on the screw assembly.
Fastener types
A bolt with a rounded head and a square section beneath it that helps resist rotation in a suitable hole. Commonly used in wood and wood-to-metal assemblies. The square neck must engage the material for the bolt to tighten properly.
Fastener types
A nut with slots at one end that can align with a cross-drilled hole in a bolt or stud for a cotter pin. The pin provides mechanical retention. Match the nut style and installation procedure to the specified assembly.
Threads & sizing
The standard larger-pitch thread series for a given diameter within a thread system. Inch Unified coarse threads are designated UNC. Coarse and fine threads of the same diameter do not mate; match the complete thread designation.
Fastener types
A screw designed to engage concrete or another approved masonry material through a correctly sized drilled hole. Hole diameter, embedment, and installation requirements depend on the specific product. It is not interchangeable with a general-purpose wood or sheet metal screw.
Heads & drives
A conical recess in a hole that accepts the tapered underside of a countersunk screw head. The term also describes the cutting tool used to make that recess. Match the angle and recess size to the screw; a countersink differs from a cylindrical counterbore.
Fastener types
An elongated internally threaded nut used to connect compatible externally threaded parts, such as sections of threaded rod. Match diameter, pitch, thread direction, and material requirements. Adequate thread engagement is necessary on both sides of the connection.
Fastener types
A screw intended for decking or related wood construction applications. Drive, thread, point, and corrosion protection vary by product. Select a screw compatible with the decking material, treatment chemicals, and exposure; the name alone does not establish structural approval.
Threads & sizing
The size measured across a fastener. For an externally threaded screw or bolt, nominal diameter refers to its designated thread size, not the head width. Confirm whether a drawing calls for thread diameter, shank diameter, or another dimension.
Heads & drives
The feature used by a tool to turn a screw or bolt, such as a slot, Phillips recess, hex socket, or six-lobe recess. Drive type is separate from head shape: a pan head screw, for example, can be made with several different drives.
Fastener types
An internally threaded expansion anchor commonly installed in a drilled hole in concrete. It is set with the specified setting tool before a compatible bolt or threaded rod is installed. Hole dimensions, embedment, and approved base materials depend on the anchor model.
Fastener types
A screw intended for attaching gypsum board to compatible framing. Coarse-thread and fine-thread designs suit different substrates, and some metal-framing screws use drill points. Choose the specified product for the framing material rather than using drywall screws as general structural fasteners.
Fastener types
A bolt with a loop-shaped head used as an attachment point. Designs range from general hardware to rated lifting products. A lifting application requires the correct rated product and installation conditions; a threaded eye alone does not establish lifting capacity.
Threads & sizing
The specified length of a screw or bolt, measured according to its head style and product standard. Most projecting-head screws are measured from beneath the head to the tip; flat countersunk screws generally include the head. Check the applicable measurement convention, especially for oval heads and shoulder screws.
Fastener types
A flat washer with a relatively large outside diameter compared with its hole. It spreads clamping force over a wider area and can cover an oversized hole. Confirm both the inside and outside diameters when ordering.
Threads & sizing
A smaller-pitch thread series than coarse thread at the same nominal diameter. Inch Unified fine threads are designated UNF. Fine thread is not interchangeable with coarse thread; verify the thread count or metric pitch before choosing a mating part.
Fastener types
A bolt with an enlarged flange beneath its head to provide a wider bearing surface. Flanges may be smooth or serrated. A serrated flange and a smooth flange behave differently at the joint surface, so match the required design and dimensions.
Fastener types
A nut with an integral flange that provides a larger bearing surface than a conventional nut body. Some versions have serrations beneath the flange. Not every flange nut is a locking nut; select the specified smooth or serrated design.
Heads & drives
A screw head with a flat top and a tapered underside, intended to sit flush in a matching countersunk hole. The countersink angle must match the screw. Flat head describes the head shape, not whether the drive is slotted, Phillips, or another style.
Fastener types
A flat ring placed beneath a bolt head, screw head, or nut to provide a bearing surface and distribute clamping force. Washers with the same nominal bolt size may have different outside diameters and thicknesses. Check the required pattern and material.
Threads & sizing
Describes a fastener threaded along essentially its full usable shank length, subject to its design and standard. Full threading can provide flexibility in engagement location, but it does not automatically make a fastener stronger than a partially threaded alternative.
Materials & finishes
Surface damage that occurs when contacting metal surfaces adhere and tear during movement. It can cause threaded parts, particularly some stainless steel combinations, to seize during tightening. Material pairing, installation speed, and suitable lubrication affect the risk.
Threads & sizing
The material-thickness range a rivet or insert is designed to clamp or accommodate. For a blind rivet, check the combined thickness of the materials being joined. Diameter and overall fastener length do not replace the need to confirm grip range.
Fastener types
A double-ended fastener with wood-screw threads at one end and machine threads at the other. The wood-thread end engages a suitable base, while the machine-thread end accepts a matching nut or threaded component. Confirm both thread sections and installation requirements.
Fastener types
An externally threaded fastener with a six-sided head for wrench or socket installation. Commonly used with a nut or tapped hole. The product specification determines dimensions, strength, and thread length; check these details when comparing it with a hex bolt or tap bolt.
Fastener types
An internally threaded nut with six wrenching flats, used with a compatible bolt, screw, or threaded rod. Match diameter, pitch or thread count, material, and strength requirements. Standard, heavy, and thin hex nuts have different dimensions and are not automatic substitutes.
Heads & drives
An internal recess with six straight sides, turned with a matching hex key or bit. Often called an Allen-style drive. It differs from a six-lobe drive; choose the exact inch or metric tool size to avoid damaging the recess.
Materials & finishes
A zinc coating applied by immersing a steel part in molten zinc. Commonly specified for outdoor corrosion protection. Its coating thickness affects thread fit, so use compatible galvanized mating components instead of assuming standard plated nuts will fit.
Fastener types
A nut that is thinner than a standard nut of the same general size. It is used where clearance is limited or as part of a two-nut locking arrangement. Thickness and load capacity differ from a standard nut; follow the assembly requirements.
Fastener types
A nut assembled with a captive, freely rotating toothed lock washer. It combines two components for convenient handling during assembly. Washer style, material, and finish should match the joint requirements; it differs from a nylon insert lock nut.
Fastener types
A heavy wood-thread screw, often called a lag bolt, typically installed with a wrench or socket. It engages wood rather than a standard machine-thread nut. Pilot-hole size and embedment depend on the screw, wood, and connection design.
Fastener types
A nut incorporating a feature intended to resist unintended rotation, such as a nylon insert or a deformed all-metal thread. Designs differ in temperature limits, installation behavior, and reuse requirements. Select the specified locking type rather than assuming all lock nuts perform alike.
Fastener types
A screw with machine threads designed to mate with a matching nut or tapped hole. Available in many head and drive styles. Match diameter and thread pitch or thread count; a machine screw generally does not create its own mating threads.
Threads & sizing
A thread system whose dimensions are expressed in millimeters. In M6 × 1.0 × 20, M6 identifies the nominal diameter, 1.0 is the pitch, and 20 is the nominal length in millimeters. Confirm pitch even when a product description omits it.
Fastener types
A nut containing a nylon collar that creates resistance as the mating thread passes through it. The insert helps resist rotation but has temperature and chemical limits. Verify the specified performance and reuse requirements for the application.
Heads & drives
A security screw with an asymmetric slotted drive that accepts a conventional slotted driver for tightening but resists normal reverse driving. Removal can require a dedicated method or tool. Consider future service access before choosing this drive.
Heads & drives
A countersunk screw head with a rounded top that remains visible above the surface. It combines a tapered underside with a raised finished appearance. It differs from a flat head, whose top is intended to sit flush in a matching countersink.
Heads & drives
A screw head with a flat bearing surface underneath and a rounded upper profile. It sits above the work surface rather than in a countersink. Specify the drive separately, since pan head screws are available with different recesses.
Threads & sizing
Describes a fastener with both a threaded portion and an unthreaded shank. Thread length can vary with overall length and the applicable standard. Check the unthreaded section against the joint thickness when the shank location matters.
Materials & finishes
A chemical treatment used on stainless steel to remove free iron contamination and promote a clean, corrosion-resistant surface. It is not a zinc coating and does not change the base alloy. Specify the required treatment and acceptance requirements when documentation matters.
Heads & drives
A cross-shaped screw recess designed for a matching Phillips driver. The driver size must fit the recess correctly. Similar-looking cross recesses, including Pozidriv and Frearson, use different geometry and should not be assumed interchangeable.
Threads & sizing
A prepared hole that guides a screw and helps control how it engages the material. Its size depends on the screw design and base material. A pilot hole is different from a clearance hole, which allows a fastener to pass through without thread engagement.
Heads & drives
A six-lobe screw recess with a center pin that prevents a standard solid six-lobe bit from seating. It requires a compatible bit with a center hole. This is different from a pin-in hex socket, which has six straight sides rather than six lobes.
Fastener types
A threaded insert that is deformed in a prepared hole to create a captive internal thread, often in sheet metal or tubing. Commonly installed from one side. Match the hole shape, grip range, thread size, and installation tool to the insert.
Fastener types
A fastener designed to discourage unauthorized removal through a special drive, break-away feature, or other design. Also called a tamper resistant fastener. Select the fastener and matching installation tool together, and consider whether later authorized removal is required.
Fastener types
A threaded nut pressed into a properly sized hole in sheet material, where displaced sheet metal mechanically retains it. It requires compatible sheet thickness and hardness. It is installed differently from a rivet nut and should not be treated as an interchangeable substitute.
Fastener types
A screw with a drill-shaped point that makes a hole and then forms mating threads in a suitable material. The point must be rated for the material and drilling thickness. Self-drilling is a specific capability; not every self-tapping screw drills its own hole.
Fastener types
A screw designed to create its own mating threads in a suitable untapped hole by forming or cutting the material. Many types require a prepared pilot hole. The term does not, by itself, mean the screw can drill through the material.
Fastener types
A screw used to secure one component against another, such as a collar on a shaft. Often headless and driven through an internal recess. Point styles, including cup, flat, and cone points, affect contact and holding behavior.
Fastener types
A tapping screw commonly used to create mating threads in sheet metal or other suitable materials. Point and thread designs vary. Check whether a pilot hole is needed; a pointed sheet metal screw is not necessarily self-drilling.
Fastener types
A screw with a controlled-diameter unthreaded shoulder between the head and a smaller threaded end. The shoulder can provide a bearing surface, pivot, or spacing function. Specify shoulder diameter and length as well as thread size.
Materials & finishes
A copper-based alloy containing silicon, used in fasteners for selected corrosion-resistant and marine applications. It differs from brass and stainless steel in composition and mechanical properties. Confirm the alloy, strength, and compatibility with surrounding materials.
Heads & drives
An internal screw drive with six rounded lobes, engaged by a matching six-lobe bit. It is distinct from a six-sided hex socket. The standard version has no center pin; pin-in security versions require a compatible hollow bit.
Fastener types
A screw with a cylindrical head and an internal drive, commonly a hex socket. It can be installed where a wrench cannot reach the outside of the head. Confirm the material, strength specification, and available head clearance.
Fastener types
An unthreaded component that maintains a set distance between parts, often with a through-hole for a screw or bolt. Match length, inside diameter, outside diameter, and material. A threaded standoff performs a related spacing function but uses a different attachment arrangement.
Heads & drives
A security drive with two holes or recesses engaged by a matching two-pin tool. Hole spacing and tool size must match the fastener. Spanner screws and spanner nuts may require different tools, so identify the actual drive before ordering.
Fastener types
A washer formed as a split helical ring, intended to provide spring action as it is compressed in an assembly. It is distinct from toothed and conical washers. Its presence alone does not guarantee resistance to loosening under vibration.
Fastener types
A component used to hold parts a fixed distance apart, often with internal threads, external threads, or a combination of both. Common in electronics and panel assemblies. Specify body length, thread size, body shape, and thread configuration.
Materials & finishes
A designation tied to a fastener specification and its mechanical requirements. Inch grades and metric property classes use different systems and are not direct numerical equivalents. Match the required specification; a stronger fastener is not automatically a suitable replacement.
Threads & sizing
A hole containing internal threads produced with a tap. It accepts a compatible machine-threaded fastener. Diameter, pitch, thread class, and usable thread depth must suit the screw; a drilled clearance hole has a different purpose.
Fastener types
A nut with a projecting threaded barrel and a flange, commonly used to create an internal machine thread in wood or another suitable material. Pronged versions resist rotation by engaging the material. Match barrel length, thread size, and mounting style.
Fastener types
A tapping screw with cutting features that remove material to create mating threads. Cutting can produce chips, which may matter inside an assembly. Match the screw type and pilot hole to the material being fastened.
Threads & sizing
The length over which mating internal and external threads overlap in an assembly. Required engagement depends on thread geometry, materials, and the connection design. A screw that bottoms out in a blind hole may fail to clamp the joint even when it appears tight.
Threads & sizing
The axial distance between matching points on adjacent threads. Metric pitch is normally stated in millimeters: a 1.0 mm pitch advances 1.0 mm between adjacent thread crests. Diameter alone is insufficient to select a compatible screw and nut.
Fastener types
A tapping screw that forms mating threads by displacing material rather than removing it as chips. It requires a suitable material and correctly sized hole. This product type is distinct from the manufacturing process used to roll threads onto an ordinary bolt.
Fastener types
A straight rod with external threads along most or all of its length, commonly used for suspension, fastening, or connections with coupling nuts. Match diameter, thread series, material, finish, and strength specification. Cutting a rod to length may require cleaning up the cut threads.
Threads & sizing
The number of threads along one inch of an inch-series fastener. In 1/4-20, the nominal diameter is 1/4 inch and the thread count is 20 TPI. A 1/4-28 part has the same nominal diameter but will not mate with a 1/4-20 thread.
Fastener types
A screw with a head shaped for hand adjustment, often knurled or winged. Useful where a component is removed or adjusted frequently. Check head clearance and clamping requirements; hand tightening is not a controlled torque method.
Threads & sizing
The turning force applied when tightening a fastener, typically expressed in units such as inch-pounds, foot-pounds, or newton-meters. Torque is influenced by friction and is not the same as clamp load. Use the specified installation procedure and account for lubrication and finish.
Heads & drives
A screw head with a broad diameter and a relatively low rounded profile. Its wider bearing surface can be useful with thin materials. It is a different head shape from pan head, even when the drive and thread size match.
Fastener types
A U-shaped fastener with threaded ends, commonly used with nuts and sometimes a plate to retain pipe, tubing, or other components. Specify inside width, inside height, rod diameter, thread size, and material rather than relying on pipe size alone.
Threads & sizing
Unified National Coarse and Unified National Fine, two inch-series thread designations. For example, 1/4-20 is a common UNC size and 1/4-28 is a common UNF size. Match the complete designation, including any specified thread class.
Fastener types
An expansion anchor commonly used in concrete. Tightening the nut draws a tapered section into an expansion clip to grip the drilled hole. Approved concrete conditions, embedment, spacing, and installation torque are specific to the anchor model.
Fastener types
A nut with two projecting wings that allow it to be turned by hand. Often used where an assembly needs frequent adjustment or removal. Hand tightening does not ensure a specified clamp load, so confirm that it suits the connection.
Fastener types
A screw with threads designed to engage wood. Conventional wood screws and modern construction screws differ in point, shank, and thread design. Match length, material, finish, and pilot-hole requirements to the wood and intended connection.
Materials & finishes
A zinc coating applied to a fastener, commonly by electroplating, to provide sacrificial corrosion protection. Appearance and performance depend on coating thickness and supplementary treatment. Zinc plated and hot-dip galvanized finishes have different thicknesses and should not be assumed equivalent.
Materials & finishes
Zinc plated steel relies on a zinc surface coating for corrosion protection, while stainless steel derives its corrosion resistance from its alloy composition and passive surface film. They are different material choices. Compare strength requirements, exposure, finish, and mating materials before substituting one for the other.
Send the size, material, quantity, and an available part number, drawing, or photo. Contact Mutual Screw & Supply or call (201) 845-5700.
