The use of screws and bolts are different. The screw is generally used to connect the fixed parts, mostly to play the role of tightening and easy installation and removal. The strength of the screws is not so high as bolts. Bolts are stronger than bolts, so they are usually used as force-bearing parts. In other words, bolts can withstand greater forces than normal fastening. Reasonable design should allow the bolt to withstand higg tension or pressure, and not to withstand shear. In most cases, screws are used to tighten the threaded hole in a part, and are rarely used for coupling nuts. The use of bolts is just the opposite, usually tightened with the nut, less screw hole between parts and tighten.
Bolt: A type of fastener consisting of a head and a screw (cylindrical body with external threads) is to be fitted with a nut for the fastener to connect two parts with through-holes. This type of connection is called bolting.
Screw: A type of fastener consisting of a head and a screw (cylindrical body with external threads). It can be divided into three categories according to the purpose: machine screws, set screws and special purpose screws. Machine screws are mainly used for the connection between one part with internal screw hole and the other part with through hole, it does not need nut (this kind of connection is screw connection, it is detachable connection.) It can be connected with nut for fastening the two parts with a through hole between the fastening connection.Tightening screw is mainly used to fix the relative position between the two parts.Special purpose screw with eyebolt screw for lifting parts)