Hexagon socket cylindrical head screw; GB701. M14 pitch; 2mm thread length 40mm

Head diameter 20.67 mm head thickness; 13.57 mm Hexagon socket width; 12mm

If the nut has a smooth round head, it is an M30 hexagon socket head screw. The national standard number is: GB70-85

If it has a knurled head, the outer diameter of the nut should be slightly larger than 45, but It is also an M30 hexagon socket screw.

The national standards for hexagon socket bolts are as follows:

MB/T2-1985 The end of externally threaded parts of fasteners (eqvISO4753:1983)

MB/T90- 1985 Fastener acceptance inspection, marking and packaging (eqvISO3269:1984)

MB/T196-1981 Ordinary thread, basic size (diameter 1~600mm)

MB/T197-1981 Ordinary thread tolerances and fits (diameter 1~355mm)

MB/T1237-2000 Fastener marking method (eqvISO8991:1986)

Extended information:

Hexagon socket bolts are divided into ordinary and high-strength ones according to their strength levels. Ordinary hexagon socket bolts refer to grade 4.8, and high-strength hexagon socket bolts refer to grade 8.8 or above, including grade 10.9 and 12.9. Class 12.9 hexagon socket head bolts generally refer to knurled, oil-stained black hex socket head cup head screws.

The performance grades of hexagon socket bolts used for steel structure connections are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. The material of bolts of grade 8.8 and above is low carbon. Alloy steel or medium carbon steel that has been heat treated (quenched and tempered) is commonly known as high-strength bolts, and the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value and the yield strength ratio of the bolt material.

Baidu Encyclopedia-Hexagon socket head screws