Bolt, is made up of the head and the threaded rod (with external thread of the cylinder) of two parts of fastener, used for fastening the two parts with a through hole, but must be used with nuts. Such as screw off nut from bolt, and can make the two parts separately, so the bolt connection is a detachable connection.

According to the connection of the stress mode, can be divided into used in ordinary hole and used in articulation hole. Ordinary mainly bear the weight of axial stress, also can bear the weight of demand is not high horizontal stress. Used in articulation hole bolt must be cooperated with size of hole, much used in horizontal stress.

According to the head shape of bolt, it can be divided into hexagon head, round head, square head, countersunk head, etc. One of the most commonly used is the hex head bolt.

Bolt has a lot of call, may call for the screw, bolt nail, standard part, fastener, etc., but they are collectively known as bolt. Bolt in the daily life and industrial production is one of the essential parts of manufacturing. Bolt used in electronic product, mechanical product, digital product, power equipment, ship, vehicle, water conservancy project, etc. it used in mechanical product is the most widely of them, such as damper, multi-axis machine, tapping machine, drilling machine, power head, pneumatic press, machine tool, etc.