Bolts

Bolts are threaded fasteners used to assemble components by joining parts with a nut or a threaded receiving hole. They are designed to carry axial loads and are selected based on material strength, thread standard, and head style. In common practice, a bolt is inserted through aligned holes and tightened with a nut or into a tapped hole, creating a clamping force as the bolt is torqued.

Components: head, shank, thread. The head provides a bearing surface and is driven by a tool; the unthreaded portion (shank) may help alignment; the threaded portion provides the engagement. The finish may be plain, coated, or plated to resist corrosion.

Thread and size: external threads on the bolt mate with internal threads in a nut or hole. Threads are specified by diameter, pitch, and standard (imperial UNC/UNF, or metric M with coarse or fine pitches). Bolts use different strength grades, such as SAE grades 2, 5, 8 or metric 8.8, 10.9; higher numbers indicate higher strength. Materials include carbon steel, alloy steel, stainless steel, brass, and aluminum.

Head styles: hex, socket cap, button, carriage, flange, shoulder. Drive types: hex head, torx, or slotted. Common coatings include zinc plating, hot-dip galvanizing, black oxide, and stainless finishes. Standards: ISO, DIN, SAE/ANSI, JIS, and BS; product specifications cover dimensions, tolerances, and surface finish.

Applications and installation: used in machinery, construction, automotive, and electronics. Proper torque must be applied to achieve the required preload without exceeding material limits; lubrication may be used to reduce thread friction. Common caution: choose correct bolt grade, diameter, length, and thread pitch for the hole or nut; ensure clearance and alignment; verify that the bolt is not overtightened.