nutandbolt

Nut and bolt is a common fastener pair used to assemble components in machinery, automotive, and construction. A bolt is a metal rod with a head on one end and a helical thread along the shank; a nut is a hollow cylinder with internal threads that mate with the bolt's threads. Tightening the bolt into the nut draws the joined parts together and creates clamping force.

Bolts come in various head types, including hex, carriage, and button, and can be metric or imperial. Nuts likewise vary, with hex nuts being the most common; locking nuts and nylon-insert locking nuts provide resistance to loosening. Bolts and nuts are selected by material, diameter, thread pitch, length, and strength grade. Common materials are carbon steel, stainless steel, brass, and aluminum, with finishes such as zinc plating, hot-dip galvanizing, black oxide, or nickel coatings to prevent corrosion.

Threads may be coarse or fine. Coarse threads are quicker to assemble and more forgiving in softer materials; fine threads offer higher tensile strength and greater adjustability but can be harder to assemble. Standards define sizes and pitch, such as ISO metric (M), UNC/UNF in imperial, and DIN or SAE specifications.

Locking methods include lock washers, thread-locking compounds, and prevailing-torque nuts. Proper lubrication reduces galling and facilitates installation but may affect required torque values. Common applications include framing, machinery assembly, and automotive components.

In manufacturing, bolts and nuts are produced by forming or cutting threads, heat-treated for strength, and finished to suit corrosion resistance. The nut-and-bolt pair remains a versatile, reusable fastening method with thousands of variants tailored to load, environment, and material compatibility.