Screw Glossary

Screws are unassuming yet fundamental components that serve as the unsung heroes of engineering and construction. These simple machines, with their helical threads and various shapes and sizes, have been a cornerstone of human innovation for centuries. From holding together the wooden planks of ancient structures to securing the intricate components of modern-day machinery, screws play a pivotal role in nearly every facet of our lives. This glossary is a comprehensive resource that delves into the world of screws, offering insights into the diverse types, terminologies, and applications of these unassuming yet indispensable fasteners.

Understanding Screw Terminology

The world of screws is rich with terminology and jargon, often bewildering to those not intimately acquainted with the subject. This glossary aims to demystify these terms, providing concise and clear definitions to help individuals, whether professionals or enthusiasts, navigate the intricate world of screws. Whether you're interested in learning about the various thread types, head shapes, or applications of screws, this glossary serves as a valuable reference point.

Applications Across Industries

Screws are a common denominator across numerous industries, from construction and manufacturing to aerospace and electronics. Their versatility makes them an indispensable tool for engineers, builders, and DIY enthusiasts alike. In this glossary, we explore the applications of screws across these diverse sectors, shedding light on how these unassuming components are integral to everything from assembling furniture to launching spacecraft. Whether you're seeking information on specific screw types for a particular project or looking to deepen your understanding of screw mechanics, this glossary is your gateway to the world of screws.

Screw: A simple machine that converts rotational motion into linear motion with the help of threads.

Thread: The helical ridge on the surface of a screw, allowing it to grip and hold objects together.

Pitch: The distance between corresponding points on adjacent threads, indicating the tightness or coarseness of the screw.

Thread Angle: The angle between the threads and the screw's axis, typically 60 degrees for metric screws and 55 degrees for imperial screws.

Major Diameter: The largest diameter of a screw's thread.

Minor Diameter: The smallest diameter between the threads of a screw.

Crest: The highest point of a thread.

Root: The lowest point of a thread.

Thread Form: The shape of the thread, commonly V-thread or square thread.

Thread Profile: The cross-sectional shape of the thread, often V-shaped or rounded.

Lead: The linear distance a screw advances with one complete rotation.

Single-Start Thread: A screw with a single helical thread.

Double-Start Thread: A screw with two parallel helical threads.

Right-Hand Thread: Threads that advance with clockwise rotation.

Left-Hand Thread: Threads that advance with counterclockwise rotation.

Acme Thread: A trapezoidal thread used for high-load applications and power transmission.

Buttress Thread: A thread with asymmetrical flanks designed for high axial loads.

Square Thread: A thread with a square cross-section, providing high efficiency and power transmission.

Unified Thread Standard: A standardized system for thread sizes in the United States.

Metric Thread Standard: A standardized system for thread sizes based on the metric system.

ISO Thread: International thread standards set by the International Organization for Standardization (ISO).

Wood Screw: A screw designed for fastening wood, featuring a sharp point and coarse threads.

Sheet Metal Screw: A screw for securing metal sheets, typically featuring a sharp, self-tapping point.

Machine Screw: A threaded fastener designed to be used with a nut or tapped hole.

Self-Tapping Screw: A screw that can tap its threads into a material without the need for pre-drilling.

Lag Screw: A heavy-duty wood screw with a hexagonal head.

Deck Screw: A specialized screw designed for outdoor deck construction.

Drywall Screw: A screw with a bugle head and fine threads for attaching drywall to studs.

Concrete Screw: A screw specifically engineered for anchoring into concrete or masonry.

Cap Screw: A screw with a hexagonal head and machine thread used with a nut or threaded hole.

Bolt: A fastener with a head and a threaded shaft, used with a nut.

Nut: A component with internal threads that mates with a bolt or screw.

Washer: A flat, typically circular, disk used to distribute load under a bolt or nut.

Thread Locker: An adhesive used to secure screws and prevent them from loosening due to vibration.

Threaded Insert: A component that adds threads to a material lacking internal threading.

Set Screw: A screw used to secure an object within or against another object.

Countersunk Screw: A screw with a head that sits flush with the surface when fully inserted.

Pan Head Screw: A screw with a rounded, low-profile head.

Oval Head Screw: A screw with a head that is slightly rounded on top.

Truss Head Screw: A screw with a wide, rounded head, used for load distribution.

Socket Head Cap Screw: A screw with a cylindrical head and a hexagonal socket.

Phillips Head Screw: A screw with a cross-shaped recess for a Phillips screwdriver.

Slotted Screw: A screw with a single straight slot for a flat-blade screwdriver.

Torx Screw: A screw with a star-shaped recess for a Torx screwdriver.

Hex Head Screw: A screw with a hexagonal head, also known as a hex bolt.

Wing Screw: A screw with two large, flat wings for hand-tightening.

Thumb Screw: A screw with a head designed to be tightened or loosened by hand.

Machine Thread: Threads designed for use with nuts or internal threads.

Wood Thread: Threads designed for gripping and securing in wood.

Plastic Screw: A screw made of plastic, often used in non-load-bearing applications.

Shoulder Screw: A screw with a cylindrical shoulder between the head and the threaded portion, used for precise spacing and alignment.

Thread Relief: A groove or clearance at the root of a thread to reduce friction and prevent galling.

Thread Engagement: The portion of a screw's thread that's in contact with a threaded hole or nut.

Pitch Diameter: The diameter where the width of the thread and the depth of the thread are equal.

Threaded Rod: A long, straight bar with continuous external threads, used for fastening or suspension applications.

Threaded Insert Tool: A tool used to install threaded inserts into materials.

Helix Angle: The angle between the threads and a plane perpendicular to the screw's axis.

Pitch Gauge: A tool used for measuring the pitch of a screw's threads.

Lead Screw: A screw used to translate rotational motion into linear motion, often found in machinery and linear actuators.

Anti-Backlash Nut: A nut designed to minimize play or backlash in lead screw systems.

Threaded Flange: A flange with internal threads designed to attach to a pipe or fitting.

Square-Neck Bolt: A bolt with a square neck just below the head, used for holding objects in place.

Half Threaded Screw: A screw with only a portion of its length featuring threads.

Drywall Anchor: An insert used to provide stability when attaching items to drywall.

Metric Thread Pitch: The distance between threads in a metric screw, specified in millimeters.

Imperial Thread Pitch: The distance between threads in an imperial (inch-based) screw, specified in threads per inch (TPI).

Screw Jack: A mechanical device for lifting heavy loads using a lead screw.

Worm Gear Screw Jack: A specific type of screw jack that incorporates a worm gear for increased efficiency.

Tapping Screw: A self-drilling screw used to cut threads in a material while fastening.

Thread Forming Screw: A screw designed to create threads in a material without the need for tapping.

Square-Drive Screw: A screw with a square recess for a square-drive screwdriver.

Knurled Screw: A screw with a textured, cylindrical head for hand-tightening.

Slotted Cheese Head Screw: A screw with a slotted head and a slightly rounded, cylindrical shape.

Spanner Screw: A screw with a unique head requiring a specialized spanner bit or tool.

Binder Head Screw: A screw with a low-profile, large-diameter head, often used in binding applications.

Friction Grip Screw: A screw with a serrated, washer-like head for increased friction and grip.

Fillet Radius: The rounded portion where the screw head meets the shank.

Self-Drilling Screw: A screw with a drill point, eliminating the need for pre-drilling in some materials.

Rivet Nut: A nut with a flanged base, used to provide a threaded insert in thin materials.

Drive Style: The type of tool or driver required to install or remove a screw, e.g., Phillips, Torx, or hex.

Shoulder Bolt: A screw with a shoulder between the head and the threaded portion, often used for precision applications.

Triangular Thread: A thread with a triangular cross-section, less common but known for high load-bearing capacity.

Thread Pitch Gauge: A tool used to measure the pitch of screw threads accurately.

Helicoil Insert: A threaded coil insert used to repair damaged threads or reinforce threaded holes.

Barrel Screw: A screw with a cylindrical head, often used in binding and adjusting applications.

Grub Screw: A small, headless screw designed to secure one object within another.

Cam-Out: The tendency of a screwdriver or bit to slip out of the screw's recess.

Cross Recess: A screw head with a cross-shaped recess, used in Phillips and Pozidriv screws.

Hex Key: A tool used to tighten or loosen hexagonal socket head cap screws.

Security Screw: A screw designed to deter tampering or unauthorized removal, often requiring specialized tools.

Barrel Nut: A nut with a cylindrical shape, commonly used in furniture assembly.

Screw Thread Micrometer: A precision measuring tool for checking thread pitch and dimensions.

Unified Thread: A thread system commonly used in the United States, Britain, and Canada.

Unified Thread Standard (UTS): A system of thread standards encompassing Unified National, Unified National Extra Fine, and Unified National Fine threads.

Screw Shank: The unthreaded portion of a screw between the head and the threaded section.

Lag Bolt: A heavy-duty screw with a hexagonal head used for securing heavy materials.

Captive Screw: A screw designed to remain attached to an object even when fully loosened.

Resin Anchor: A fastening system that uses epoxy or resin to secure screws in concrete or masonry.

Thread Gauge: A tool for measuring thread size, pitch, and other parameters.

Anti-Corrosion Coating: A protective layer applied to screws to resist rust and corrosion in harsh environments.