JIS B 1181 - 2004 Dip Press Sanitary Galvanized Thick M5 M6 0.75 Aluminium Hex Nuts
According to the nominal thickness of the hexagon nut is divided into I, II and thin three types. Nuts above grade 8 are divided into two types: type 1 and type II. Type I hexagon nuts are the most widely used, and type 1 nuts are divided into A, B, C three levels, of which A and B level nuts are suitable for small surface roughness and high precision requirements of machines, equipment and structure, while C level nuts are used for rough surface and low precision requirements of machines, equipment or structure; Type 2 hexagon nut thickness is thicker, more often in the need to assemble and disassemble the occasion.