Glossary

A lag bolt (also called a lag screw) is a large, heavy-duty fastener with a hex head and a coarse threaded shaft, designed to be driven into wood or other soft materials to create a strong, load-bearing connection.

A Large Hex Serrated Flange Locking Machine Screw is a type of fastener designed for heavy-duty applications where a secure, vibration-resistant connection is necessary. It combines a large hexagonal head with a serrated flange that provides a locking function without needing additional washers. This screw is commonly used in industrial and construction settings, where strong, reliable fastening is required.

A large hex serrated flange nut is a type of fastener that combines a hexagonal shape with an integrated flange at the base, along with serrations on the flange. This design enhances the nut's grip on the material and provides resistance to loosening due to vibration or movement, making it especially useful in heavy-duty applications.

The initial, partially formed, or tapered threads at the very end of a screw or bolt. These are designed to help guide the fastener into a nut or tapped hole. Its primary purpose is to facilitate easy engagement and proper alignment, thereby reducing the likelihood of cross-threading during assembly.

Threads that tighten when turned counterclockwise (to the left). These are less common than right-handed threads and are used in applications where rotation or motion could cause a right-handed thread to loosen.

The measurement of a fastener from the bottom of the head to the end of the threaded or unthreaded shank.

A type of fastener designed to resist loosening caused by excessive vibration. Lock nuts employ various locking mechanisms, including nylon inserts, distorted threads, or metal deformation, to maintain a secure hold. They are commonly used in applications that experience high levels of movement and must remain tight despite these changing forces.

A Lockwasher DIN 127B is a split lock washer (also known as a helical spring lock washer) designed according to the DIN 127B standard, which defines the dimensions, materials, and specifications for this type of lock washer. It is commonly used to prevent fasteners from loosening due to vibration or dynamic loads.

Loctite® is Henkel’s well-known line of industrial adhesives and sealants, best recognized for anaerobic threadlockers that cure without air when confined between metal threads. Brushed onto a bolt or nut, the liquid fills thread gaps, then polymerizes with the help of metal ions to lock the joint against vibration, seal out leaks and corrosion, and help maintain clamp load. Grades vary by strength and behavior: purple is low strength for tiny screws, blue is medium and removable with hand tools (243 is oil-tolerant), red is high strength and typically needs heat to break, and green is a thin “wicking” formula that penetrates pre-assembled fasteners.

Beyond threadlockers, the Loctite brand also includes retaining compounds for shafts and bearings, pipe thread sealants, gasketing products, cyanoacrylate instant adhesives, epoxies, structural acrylics, and silicones. Performance—such as temperature limits, oil tolerance, and cure speed—depends on the specific grade and substrate, and primers can help on passive metals like stainless or zinc-plated parts.

A specific quantity of fasteners that are manufactured, processed, or packaged under the same conditions and grouped together for identification and quality control. A lot typically shares the same material, production run, heat treatment, and inspection records to ensure consistency and traceability.

A quality control method used to evaluate a batch (or “lot”) of fasteners by inspecting a representative subset. Instead of testing every item, a specific number of parts are randomly selected and checked for defects or compliance with specifications. The results help determine whether the entire lot meets quality standards or needs to be rejected or reprocessed.