Basic characteristics of different standard screw

Different introduction to the basic features of standard screws, screw except for some basic dimensions such as head to the side, head of different thickness, most notably threaded portion is different. GB, DIN, JIS and thread are all in MM (mm) for units, collectively known as the metric thread. As ANSI, ASME and other threads are in inches, called American standard threads. In addition to metric thread and American thread there is a BSW-the British standard, its thread is in inch units, commonly known as the Whitworth thread. Metric threads are in MM (mm) as a unit, it's cusp angle of 60 degrees. American thread and imperial units are in inches. Us the cusps of the thread angle is 60 degrees, the cusp of inch thread angle is 55 degrees. Due to the different units of measurement, resulting in a variety of thread representation are not the same. Like for example M16-2X60 is expressed in metric thread. His specific effect that the nominal diameter of the screw is 16MM, the pitch is 2MM, the length of 60MM, such as: 1/4-20X3/4 is expressed in inch thread, he means the nominal diameter of the screw is 1/4 inches (one inch =25.4MM), have 20 teeth in one inch, length 3/4 inch.