8.8 10.9 12.9 High strength bolts, black large hexagonal bolts
Production parameter
| thread specification d |
(M39) | M42 | (M45) | M48 | (M52) | M56 | M64 | |
| P | pitch | 4 | 4.5 | 4.5 | 5 | 5 | 5.5 | 6 |
| b | reference | 68 | 74 | 76 | 82 | 85 | 90 | 100 |
| c | Min | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 |
| Max | 1 | 1 | 1 | 1 | 1 | 1 | 1 | |
| da | Max | 45 | 48 | 52 | 55 | 60 | 64.2 | 73.2 |
| ds | nominal | 39 | 42 | 45 | 48 | 52 | 56 | 64 |
| Min | 38 | 41 | 44 | 47 | 51 | 54.8 | 62.8 | |
| Max | 40 | 43 | 46 | 49 | 53 | 57.2 | 65.2 | |
| dw | Min | 60 | 64.7 | 69.45 | 74.2 | 78.8 | 83.4 | 92.9 |
| e | Min | 71.3 | 76.95 | 82.6 | 88.25 | 93.79 | 99.2 | 110.5 |
| k | nominal | 25 | 26 | 28 | 30 | 33 | 35 | 40 |
| Min | 23.95 | 24.95 | 26.95 | 28.95 | 31.75 | 33.75 | 38.75 | |
| Max | 26.05 | 27.05 | 29.05 | 31.05 | 34.25 | 36.25 | 41.25 | |
| k1 | Min | 16.76 | 17.46 | 18.86 | 20.26 | 22.23 | 23.63 | 27.13 |
| r | Min | 2.5 | 2.5 | 3 | 3 | 3.5 | 3.5 | 4 |
| s | Max=nominal | 65 | 70 | 75 | 80 | 85 | 90 | 100 |
| Min | 63.1 | 68.1 | 73.1 | 78.1 | 83 | 87.8 | 97.8 | |
| Thread b | - | - | - | - | - | - | - | |
Production description
Bolts made of high-strength steel or requiring significant pre tightening force can be referred to as high-strength bolts. High strength bolts are commonly used for connecting bridges, steel rails, high-voltage and ultra-high voltage equipment. The fracture of this type of bolt is mostly brittle fracture. High strength bolts applied to ultra-high pressure equipment require significant prestressing to ensure the sealing of the container.
Some concepts about high strength bolts
According to the provisions of the bolt performance grade in 8.8 or above, known as high-strength bolts. As of March 2020, China's national standard only listed to M68. For large size specifications, especially the length of the bolt itself 10 ~ 15 times of high-strength bolts, finished products are rare, a small number of domestic manufacturers in China can be customized. [1-2][3] high-strength bolt and ordinary bolt difference: high-strength bolt is able to withstand the load than the same specification of ordinary bolt to be greater. The material of ordinary bolts is made of Q235(A3) . High strength bolt material 35 # steel or other high-quality materials, made after heat treatment, improve the strength.