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The hex bolt manufactured in accordance with ASME B18.2.1 has taken dominance in headed style bolt. It is one of the most widely applied head styles which has a hexagonal head from the top view. Compared to square head bolt, the six-sided head of hex bolt requires smaller tightening angle of each stroke hence may facilitate the assembly of bolted joint by a wrench. When being tightened, the contact surface between the wrench and head of the hex bolt is comparatively larger than that of a eight-sided (octagonal) head. This may provide a firm grip by the wrench.
A typical drawing of hex bolt conforming to ASME B18.2.1
Generally, a hex bolt can be designated as Hex bolt per ASME B18.2.1, 1/2″ – 16 × 4-1/2″, ASTM A193 Grade B7, galvanized. It indicates that nominal size – 1/2″, threads per inch – 16, bolt length – 4-1/2″. The weight of a hex bolt can be calculated using the following equation: Weighthex = ρ × [3 × 31/2 ÷ 8 × G2 + πE2L/4], ρ is the density of bolt material.
Nominal Size | E | H | |||
Max. | Min. | Basic | Max. | Min. | |
1/4 | 0.260 | 0.237 | 11/64 | 0.188 | 0.150 |
5/16 | 0.324 | 0.298 | 7/32 | 0.235 | 0.195 |
3/8 | 0.388 | 0.360 | 1/4 | 0.268 | 0.226 |
7/16 | 0.452 | 0.421 | 19/64 | 0.316 | 0.272 |
1/2 | 0.515 | 0.482 | 11/32 | 0.364 | 0.302 |
5/8 | 0.642 | 0.605 | 27/64 | 0.444 | 0.378 |
3/4 | 0.768 | 0.729 | 1/2 | 0.524 | 0.455 |
7/8 | 0.895 | 0.852 | 37/64 | 0.604 | 0.531 |
1 | 1.022 | 0.976 | 43/64 | 0.700 | 0.591 |
1-1/8 | 1.149 | 1.098 | 3/4 | 0.780 | 0.658 |
1-1/4 | 1.277 | 1.223 | 27/32 | 0.876 | 0.749 |
1-3/8 | 1.404 | 1.345 | 29/32 | 0.940 | 0.810 |
1-1/2 | 1.531 | 1.470 | 1 | 1.036 | 0.902 |
1-5/8 | 1.658 | 1.591 | 1-3/32 | 1.116 | 0.978 |
1-3/4 | 1.785 | 1.716 | 1-5/32 | 1.196 | 1.054 |
1-7/8 | 1.912 | 1.839 | 1-1/4 | 1.276 | 1.130 |
2 | 2.039 | 1.964 | 1-11/32 | 1.388 | 1.175 |
2-1/4 | 2.305 | 2.214 | 1-1/2 | 1.548 | 1.327 |
2-1/2 | 2.559 | 2.461 | 1-21/32 | 1.708 | 1.479 |
2-3/4 | 2.827 | 2.711 | 1-13/16 | 1.869 | 1.632 |
3 | 3.081 | 2.961 | 2 | 2.060 | 1.815 |
3-1/4 | 3.335 | 3.210 | 2-3/16 | 2.251 | 1.936 |
3-1/2 | 3.589 | 3.461 | 2-5/16 | 2.380 | 2.057 |
3-3/4 | 3.858 | 3.726 | 2-1/2 | 2.572 | 2.241 |
4 | 4.111 | 3.975 | 2-11/16 | 2.764 | 2.424 |
Nominal Size | F | G | ||
Max. | Min. | Max. | Min. | |
1/4 | 0.438 | 0.425 | 0.505 | 0.484 |
5/16 | 0.500 | 0.484 | 0.577 | 0.552 |
3/8 | 0.562 | 0.544 | 0.650 | 0.620 |
7/16 | 0.625 | 0.603 | 0.722 | 0.687 |
1/2 | 0.750 | 0.725 | 0.866 | 0.826 |
5/8 | 0.938 | 0.906 | 1.083 | 1.033 |
3/4 | 1.125 | 1.088 | 1.299 | 1.240 |
7/8 | 1.312 | 1.269 | 1.516 | 1.447 |
1 | 1.500 | 1.450 | 1.732 | 1.653 |
1-1/8 | 1.688 | 1.631 | 1.949 | 1.859 |
1-1/4 | 1.875 | 1.812 | 2.165 | 2.066 |
1-3/8 | 2.062 | 1.994 | 2.382 | 2.273 |
1-1/2 | 2.250 | 2.175 | 2.598 | 2.480 |
1-5/8 | 2.438 | 2.356 | 2.815 | 2.616 |
1-3/4 | 2.625 | 2.538 | 3.031 | 2.893 |
1-7/8 | 2.812 | 2.719 | 3.248 | 3.099 |
2 | 3.000 | 2.900 | 3.464 | 3.306 |
2-1/4 | 3.375 | 3.262 | 3.897 | 3.719 |
2-1/2 | 3.750 | 3.625 | 4.330 | 4.133 |
2-3/4 | 4.125 | 3.988 | 4.763 | 4.546 |
3 | 4.500 | 4.350 | 5.196 | 4.959 |
3-1/4 | 4.875 | 4.712 | 5.629 | 5.372 |
3-1/2 | 5.250 | 5.075 | 6.062 | 5.786 |
3-3/4 | 5.625 | 5.437 | 6.495 | 6.198 |
4 | 6.000 | 5.800 | 6.928 | 6.612 |
Nominal Size | R | LT | ||
Max. | Min. | L ≤ 6" | L > 6" | |
1/4 | 0.03 | 0.01 | 0.750 | 1.000 |
5/16 | 0.03 | 0.01 | 0.875 | 1.125 |
3/8 | 0.03 | 0.01 | 1.000 | 1.250 |
7/16 | 0.03 | 0.01 | 1.125 | 1.375 |
1/2 | 0.03 | 0.01 | 1.250 | 1.500 |
5/8 | 0.06 | 0.02 | 1.500 | 1.750 |
3/4 | 0.06 | 0.02 | 1.750 | 2.000 |
7/8 | 0.06 | 0.02 | 2.000 | 2.250 |
1 | 0.09 | 0.03 | 2.250 | 2.500 |
1-1/8 | 0.09 | 0.03 | 2.500 | 2.750 |
1-1/4 | 0.09 | 0.03 | 2.750 | 3.000 |
1-3/8 | 0.09 | 0.03 | 3.000 | 3.250 |
1-1/2 | 0.09 | 0.03 | 3.250 | 3.500 |
1-5/8 | 0.09 | 0.03 | 3.500 | 3.750 |
1-3/4 | 0.12 | 0.04 | 3.750 | 4.000 |
1-7/8 | 0.12 | 0.04 | 4.000 | 4.250 |
2 | 0.12 | 0.04 | 4.250 | 4.500 |
2-1/4 | 0.19 | 0.06 | 4.750 | 5.000 |
2-1/2 | 0.19 | 0.06 | 5.250 | 5.500 |
2-3/4 | 0.19 | 0.06 | 5.750 | 6.000 |
3 | 0.19 | 0.06 | 6.250 | 6.500 |
3-1/4 | 0.19 | 0.06 | 6.750 | 7.000 |
3-1/2 | 0.19 | 0.06 | 7.250 | 7.500 |
3-3/4 | 0.19 | 0.06 | 7.750 | 8.000 |
4 | 0.19 | 0.06 | 8.250 | 8.500 |
For L ≤ 6″, LT equals twice the basic thread diameter plus 0.25″; For L > 6″, LT equals twice the basic thread diameter plus 0.50″. For bolts that are threaded full length, LG defines the unthreaded length under the head, and LG ≤ 2.5 × P for sizes ≤ 1″ while LG ≤ 3.5 × P for sizes > 1″ (P = thread pitch). If bolt size ≤ 1″ and L ≤ LT + 2.5 × P, or, if bolt size > 1″ and L ≤ LT + 3.5 × P, the bolt shall be threaded for full length.
ASME B18.2.1 Nine Types of Bolts & Screws | ||
---|---|---|
Square Head Bolt | Hex Bolt | Heavy Hex Bolt |
Askew Head Bolt | Hex Cap Screw | Heavy Hex Screw |
Hex Flange Screw | Lobed Head Screw | Lag Screw |