Hexagon bolts have three grades

In fact, hexagon bolts have three grades: A, B and C, with the following differences.
Hexagon bolts are divided into three grades: grade A, grade B and grade C. Bolt connection can be divided into ordinary bolt connection and high-strength bolt connection. Ordinary bolts can be classified into grades A, B and C. Here, Grade A, B and C refer to the tolerance grade of bolts, Grade A is precision grade, Grade B is ordinary grade, and Grade C is loose grade. Do you know the difference between the three grades?

Grade A and B are refined bolts, and grade C is rough bolts. Class A and B refined bolts have smooth surface, accurate size, high requirements for hole forming quality, complex fabrication and installation, and high price, which are rarely used in steel structures. The difference between grade A and B refined bolts is only the length of the bolt rod. Grade C bolts can generally be used for the connection of tension along the bolt rod axis, as well as the shear connection of the secondary structure or temporary fixation during installation.

Class A is used in important places with high assembly accuracy and places subject to large impact, vibration or variable load. Class A is used for bolts with d=1.6-24mm and l ≤ 10d or l ≤ 150mm. Grade B is used for bolts with d>24mm or l>10d or l ≥ 150mm. Grade B of thin rod is M3-M20 hexagonal flange bolt with better anti-loosening performance. Class C is between M5-M64. Grade C hexagon bolts are mainly used in steel construction machinery and equipment with relatively rough appearance and low requirements for accuracy. Generally, Grade C accuracy is selected for common connections.

Grade A and B hexagon bolts are mainly used in machinery and equipment with smooth appearance and high precision requirements. The executive standards are as follows: Torsional shear type high-strength bolt connection pairs for steel structures GB/T3632-1995; High strength large hexagon head bolts for steel structures GB/T1228 – 1991; High Strength Large Hexagon Nuts for Steel Structures (GB/T1229-1991); High strength washers for steel structures GB/T1230 – 1991; Technical Conditions for High Strength Large Hexagon Head Bolts, Large Hexagon Nuts and Washers for Steel Structures (GB/T1231-1991). Product technical performance and executive standard The product is manufactured in strict accordance with DIN, ISO, ANSI, JIS, AS, NF, GB/T and other standards. The strength grade can reach 4.4~12.9, and the steel structure can reach 8.8S and 10.9S</ p> In a word, the accuracy of bolts is different, and the yield strength is also different. Our common mechanical structure is basically enough to choose Grade C and Grade B, and the cost of Grade A will go up. Don’t underestimate these bolts. The cost of spare parts in the later stage is considerable.