DIN 931 (ISO4014) hexagonal head bolts with shank, also called semi-threaded hexagonal bolts or half threaded hexagonal bolts, according to the thread length. DIN 931 hexagon bolts are often used in conjunction with hex nuts. the tow parts are connected into a whole by threaded connection, which is a detachable connection. the self-locking performance of the fine thread hexagonal bolt is better, and it is mostly used for parts subject to greater impact, vibration or alternating load, can also be used for fine adjustment mechanism.