Fasteners generally comprise 12 categories of parts: bolts, studs, screws, nuts, self-tapping screws, wood screws, washers, retaining rings, pins, rivets, assemblies and connection sets, and weld studs.
Bolt: Consists of a head and a threaded shank; it must be used with a nut to join two parts featuring through-holes, forming a detachable connection.
Stud: Has no head and is threaded at both ends; one end screws into a part, while the other passes through a second part to receive a nut-suitable for applications where one of the parts is relatively thick.
Screw: Consists of a head and a threaded shank; it can be screwed directly into a threaded hole in a part without a nut, and is commonly used for positioning or fastening.
Nut: Features an internal threaded hole and is typically hexagonal in shape; it is used in conjunction with a bolt or screw to lock parts securely in place.
Self-tapping screws: Similar to machine screws, but featuring threads specifically designed for self-tapping applications. They are used to fasten two thin metal components into a single assembly. Small pilot holes must be pre-drilled in the components; due to their high hardness, these screws can be driven directly into the holes, cutting or forming matching internal threads within the material.
Wood screws: Also similar to machine screws, but featuring threads specifically designed for wood. They can be driven directly into wooden components (or parts) to fasten a metal (or non-metal) part-featuring a through-hole-to a wooden component. This type of connection is detachable.
Washers: A category of fasteners shaped like flat rings. Placed between the bearing surface of a bolt, screw, or nut and the surface of the connected part, they serve to increase the contact area, reduce pressure per unit area, and protect the surface of the connected part from damage. Another type-elastic washers-also serves to prevent nuts from loosening.
Retaining rings: Designed for installation in grooves on shafts or within bores (holes) of machinery and equipment; they prevent components mounted on the shaft or within the bore from shifting axially (moving side-to-side).
Pins: Primarily used for positioning components; some types are also used for connecting or securing parts, transmitting power, or locking other fasteners in place.
Rivets: A type of fastener consisting of a head and a shank, used to fasten two parts (or components) with holes into a single assembly. This connection method is known as riveting. It is a permanent (non-detachable) connection, as separating the joined parts requires destroying the rivet.
Assemblies and connection sets: "Assemblies" refer to a category of fasteners supplied as a combined unit-such as a machine screw (or bolt or self-tapping screw) paired with a flat washer (or spring washer or locking washer). "Connection sets" refer to fasteners supplied as a combination of specific bolts, nuts, and washers-such as high-strength, large-hex-head bolt assemblies used in steel structures.
Weld studs: A type of fastener consisting of a shank and a head (or no head); they are attached to a part (or component) via welding to facilitate subsequent connection to other parts.