Marine Engineering

A bolt is a term used for a threaded fastener designed to be used in conjunction with a  screw. A screw is a term used for a threaded fastener designed to mate with a pre-formed  internal thread or forming its own thread. Three main parts of bolt: Head Shank Thread The size of a bolt is a combination of the thread diameter and the length. The length is normally taken  from the underside of the head to the end of the thread. For example, a bolt designated as M12 x 100 indicates that the bolt is a metric thread of 12mm diameter and of 100 mm length. A full designation of the bolt usually includes the head type and the standard that the bolt is made to. For example, Hexagon head bolt DIN 6914 -M12 x 100 indicates that a standard hexagon head form is to be used, DIN 6914 refers to the standard that the bolt is to be made to (the German standard on high strength hexagon head bolts) and M12 x 100 indicates that the bolt is a metric thread of 12 mm diameter and ...