Nut fastener bolt or screw together, so it plays the role of part A in the original all manufacturing machinery must be used. Nut species variety, we have common national standard, British standard, American standard, Japanese subject nut . According to different materials, the nuts can be divided into carbon steel, high strength steel, stainless steel, steel and other major types of product attributes corresponding to countries with different standards numbers are divided into ordinary, non-standard, (old) GB, the new national standard, American , English, German standard. Different sizes, ranging from threads into different specifications. Generally GB, German standard represented by M (for example, M8, M16), American, British is expressed as a fraction or # specifications (such as # 8, # 10, 1 / 4,3 / 8) fasteners, nuts are parts of machinery and equipment will be closely linked through threaded inside, the same size nuts and screws, to connect together, for example, only M4-0.7 nut and the screw with M4-0.7 of ( in nut, M4 refers to the inner diameter of the nut is about 4mm, 0.7 refers to the distance between the two screw thread 0.7mm); US-made products also, for example, 1 / 4-20 screw and nut only 1 / 4-20 with (1/4 refers to the inner diameter of approximately 0.25 inch nut, 20 refers to every inch, 20 teeth).