Bolt

A bolt is a threaded fastener typically used with a nut or a pre-tapped hole to clamp two or more parts together. Bolts are designed to be tightened to a specific preload, stretching slightly as they are torqued so the joint stays compressed under load. Unlike many screws that are driven into a material, bolts are commonly used in through-holes where the bolt passes through the parts and the nut provides the mating threads.

Bolts are specified by thread size and pitch (or threads per inch), length, head style (such as hex head or socket head), strength grade or property class, and material and finish for corrosion resistance. Selecting the right bolt involves matching the thread type and fit, ensuring adequate thread engagement, and choosing a grade that meets the required load capacity. Proper installation, including correct torque and compatible nuts and washers, helps the bolt maintain preload and resist loosening, fatigue, and joint failure.