ASME B18.31.2 is a standard published by the American Society of Mechanical Engineers (ASME) that covers the dimensional requirements for fasteners used to construct flanged joints. These fasteners, which include bolts, screws, and studs, are designed to be used in flanged joints that are subjected to high levels of stress, such as those found in piping systems and pressure vessels.
The standard specifies fasteners' size and dimensional requirements, including thread pitch, shank diameter, head diameter, and length. It also includes specifications for the materials and finishes used in the production of these fasteners.
ASME B18.31.2 is an important standard for engineers and manufacturers working with fasteners in high-stress applications. It ensures that these fasteners are dimensionally consistent and capable of meeting the required performance standards.
| Nominal Size | BM | B | |||
|---|---|---|---|---|---|
| Tap End Thread Length | Minimum Nut End Full Thread Length | ||||
| Min | Max | L≤ 10 | 10 < L ≤ 10 | L >16 | |
| 1/4" | 8.9 | 10.16 | 19.05 | 25.4 | 38.1 |
| 5/16" | 11.18 | 12.64 | 22.23 | 28.58 | 41.28 |
| 3/8" | 13.52 | 15.08 | 25.4 | 31.75 | 44.45 |
| 7/16" | 15.75 | 17.57 | 28.58 | 34.93 | 47.63 |
| 1/2" | 17.99 | 20.11 | 31.75 | 38.1 | 50.8 |
| 9/16" | 20.38 | 22.75 | 34.93 | 41.28 | 53.98 |
| 5/8" | 22.66 | 24.96 | 38.1 | 44.45 | 57.15 |
| 3/4" | 27.31 | 29.84 | 44.45 | 50.8 | 63.5 |
| 7/8" | 31.96 | 34.74 | 50.8 | 57.15 | 69.85 |
| 1" | 36.53 | 39.67 | 57.15 | 63.5 | 76.2 |
| 1 1/8" | 41.28 | 44.45 | 63.5 | 69.85 | 82.55 |
| 1 1/4" | 46.05 | 49.22 | 69.85 | 76.2 | 88.9 |
| 1 3/8" | 50.8 | 53.97 | 76.2 | 82.55 | 95.25 |
| 1 1/2" | 55.58 | 58.75 | 82.55 | 88.9 | 101.6 |
| 1 5/8" | 60.33 | 63.5 | 88.9 | 95.25 | 107.95 |
| 1 3/4" | 65.1 | 68.27 | 95.25 | 101.6 | 114.3 |
| 1 7/8" | 69.85 | 73.02 | 101.6 | 107.95 | 120.65 |
| 2" | 74.3 | 78.1 | 107.95 | 114.3 | 127 |
| 2 1/4" | 83.82 | 87.63 | 120.65 | 127 | 139.7 |
| 2 1/2" | 93.35 | 97.15 | 133.35 | 139.7 | 152.4 |
| 2 3/4" | 102.87 | 106.68 | 146.05 | 152.4 | 165.1 |
| 3" | 112.4 | 116.2 | - | 165.1 | 177.8 |
| 3 1/4" | 121.29 | 126.36 | - | 177.8 | 190.5 |
| 3 1/2" | 130.81 | 135.89 | - | 190.5 | 203.2 |
| 3 1/4" | 140.34 | 145.41 | - | 203.2 | 215.9 |
| 4" | 149.86 | 154.94 | - | 215.9 | 228.6 |
