EXAMPLE 1: Hex bolt M12 x 1.75 x 150, class 4.6 zinc plated.
SCREW: A screw is the term used for a threaded fastener, with or without a head (headless – as in set screw) so designed as to permit it to be properly assembled in a pre formed internal threaded hole (or forming its own thread) and secured by means of tightening the head.
CAP SCREW: A term used to describe an externally threaded fastener with a protruding head, designed to be torqued by a spanner or wrench and always preceded by a head style such as ‘Hex cap screw’, ‘Socket head cap screw’ etc.
SET SCREW: A set screw is a headless threaded fastener that is typically used to hold a sleeve, collar or gear on a shaft to prevent relative motion.
NUT: A nut is a geometrically designed block (usually of metal or plastic) with an internal thread and designed to be assembled in conjunction with a bolt or screw.
PREVAILING TORQUE NUT: A type of lock nut which has a prevailing torque to assist in preventing self loosening. There are two main categories of prevailing torque nuts, all metal and nylon insert. All metal torque prevailing nuts generally gain a prevailing torque by distorting the threads at the top of the nut by some means. Nylon insert torque prevailing nuts ultilise a nylon (or other polymer) insert to achieve a prevailing torque.
WASHER: A washer is a part having a centrally located hole. The washer performs various functions when assembled between the bearing surface of a fastener and the part being attached.
MAJOR DIAMETER: This is the diameter of an imaginary cylinder parallel with the crests of the thread; in other words it is the distance from crest to crest for an external thread, or root to root, or an internal thread.