Inch-Series Askew Head Bolts with Skewed Bearing Face for Structural Beam and Sloped Flange Connections.
ASME B18.2.1 Askew Head Bolts are a specialized inch-series fastener featuring a bearing surface inclined at 9.45° (±2°), based on the 2 in 12 slope of the inner flange of American Standard beams and channels, designed to provide full bearing contact against sloped beam flanges in structural steel connections where a standard flat-seated bolt would bear unevenly and compromise clamping integrity. The dimensional standard governs all critical parameters including head dimensions, body diameter, thread length, width across flats, and head skew angle tolerances, ensuring consistent dimensional performance across all manufacturing sources. These bolts are manufactured in compliance with ASTM A1082, the specification for high-strength stainless steel bolting material, delivering excellent corrosion resistance and reliable mechanical performance in demanding structural environments. The use of ASTM A1082 material in ASME B18.2.1 Askew Head Bolts is particularly advantageous in marine, coastal, and industrial structures where carbon steel would be susceptible to severe atmospheric corrosion, significantly extending service life and reducing long-term maintenance costs. Procuring askew head bolts to both ASME B18.2.1 for dimensions and ASTM A1082 for material ensures a fully defined and traceable fastener for critical structural bolted connections.
| Nominal Size | Body Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H1 | Mid height, H | Radius of Fillet, R | Maximum Unthreaded Length, S | Nominal Thread Length for Bolt Lengths, LT | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | 152.4mm and Shorter | Over 152.4mm | ||||
| 3/8 | 0.3750 | 9.855 | 9.144 | 14.288 | 14.275 | 13.818 | 20.193 | 18.974 | 8.052 | 7.036 | 6.350 | 0.762 | 0.254 | 6.350 | 25.400 | 31.750 |
| 1/2 | 0.5000 | 13.081 | 12.243 | 19.050 | 19.050 | 18.415 | 26.949 | 25.273 | 10.439 | 9.423 | 8.331 | 0.762 | 0.254 | 7.925 | 31.750 | 38.100 |
| 5/8 | 0.6250 | 16.307 | 15.367 | 23.813 | 23.825 | 23.012 | 33.680 | 31.598 | 13.208 | 12.192 | 10.719 | 1.524 | 0.508 | 8.738 | 38.100 | 44.450 |
| 3/4 | 0.7500 | 19.507 | 18.517 | 28.575 | 28.575 | 27.635 | 40.411 | 37.948 | 15.596 | 14.580 | 12.700 | 1.524 | 0.508 | 10.312 | 44.450 | 50.800 |
| 7/8 | 0.8750 | 22.733 | 21.641 | 33.338 | 33.325 | 32.233 | 47.142 | 44.247 | 18.364 | 17.348 | 15.088 | 1.524 | 0.508 | 11.125 | 50.800 | 57.150 |
| 1 | 1.0000 | 25.959 | 24.790 | 38.100 | 38.100 | 36.830 | 53.873 | 50.571 | 20.345 | 19.329 | 16.662 | 2.286 | 0.762 | 12.700 | 57.150 | 63.500 |
| Nominal Length | Nominal Size (inches) | |||
|---|---|---|---|---|
| 1/4 to 3/8 | 7/16 and 1/2 | 9/16 to 3/4 | 7/8 and 1 | |
| Up to 25.4 mm, incl. | +0.508 0.762 |
+0.508 0.762 |
+0.508 0.762 |
... |
| Over 25.4 mm to 63.5 mm, incl. | +0.508 1.016 |
+1.016 1.524 |
+1.524 2.032 |
+2.032 2.54 |
| Over 63.5 mm to 101.6 mm, incl. | +1.016 1.524 |
+1.524 2.032 |
+2.032 2.54 |
+2.54 3.556 |
| Over 101.6 mm to 152.4 mm, incl. | +1.524 2.54 |
+2.032 2.54 |
+2.54 2.54 |
+3.048 4.064 |
| Longer than 152.4 mm | +2.54 4.572 |
+3.048 4.572 |
+3.556 4.572 |
+4.064 5.08 |
| Nominal Size | Body Diameter, E | Width Across Flats, F | Width Across Corners, G | Head Height, H1 | Mid height, H | Radius of Fillet, R | Maximum Unthreaded Length, S | Nominal Thread Length for Bolt Lengths, LT | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Basic | Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | 6 in. and Shorter | Over 6 in. | ||||
| 3/8 | 0.3750 | 0.388 | 0.360 | 9/16 | 0.562 | 0.544 | 0.795 | 0.747 | 0.317 | 0.277 | 0.250 | 0.03 | 0.01 | 0.250 | 1.000 | 1.250 |
| 1/2 | 0.5000 | 0.515 | 0.482 | 3/4 | 0.750 | 0.725 | 1.061 | 0.995 | 0.411 | 0.371 | 0.328 | 0.03 | 0.01 | 0.312 | 1.250 | 1.500 |
| 5/8 | 0.6250 | 0.642 | 0.605 | 15/16 | 0.938 | 0.906 | 1.326 | 1.244 | 0.520 | 0.480 | 0.422 | 0.06 | 0.02 | 0.344 | 1.500 | 1.750 |
| 3/4 | 0.7500 | 0.768 | 0.729 | 1 1/8 | 1.125 | 1.088 | 1.591 | 1.494 | 0.614 | 0.574 | 0.500 | 0.06 | 0.02 | 0.406 | 1.750 | 2.000 |
| 7/8 | 0.8750 | 0.895 | 0.852 | 1 5/16 | 1.312 | 1.269 | 1.856 | 1.742 | 0.723 | 0.683 | 0.594 | 0.06 | 0.02 | 0.438 | 2.000 | 2.250 |
| 1 | 1.0000 | 1.022 | 0.976 | 1 1/2 | 1.500 | 1.450 | 2.121 | 1.991 | 0.801 | 0.761 | 0.656 | 0.09 | 0.03 | 0.500 | 2.250 | 2.500 |
| Nominal Length | Nominal Size | |||
|---|---|---|---|---|
| 1/4 to 3/8 | 7/16 and 1/2 | 9/16 to 3/4 | 7/8 and 1 | |
| Up to 1 in., incl. | +0.02 0.03 |
+0.02 0.03 |
+0.02 0.03 |
... |
| Over 1 in. to 2 1/2 in., incl. | +0.02 0.04 |
+0.04 0.06 |
+0.06 0.08 |
+0.08 0.10 |
| Over 2 1/2 in. to 4 in., incl. | +0.04 0.06 |
+0.06 0.08 |
+0.08 0.10 |
+0.10 0.14 |
| Over 4 in. to 6 in., incl. | +0.06 0.10 |
+0.08 0.10 |
+0.10 0.10 |
+0.12 0.16 |
| Longer than 6 in. | +0.10 0.18 |
+0.12 0.18 |
+0.14 0.18 |
+0.16 0.20 |
ASTM A1082/A1082M (2016) Table 1 lists 14 duplex (ferritic-austenitic) grades, S31100, S31260, S31803, S32101, S32202, S32205 (2205), S32304 (2304), S32506, S32550 (255), S32750 (2507), S32760, S32906, S32950 and S39277, and 5 precipitation-hardening grades, S15700 (Type 632), S17400 (Type 630), S17600 (Type 635), S17700 (Type 631) and S35500 (Type 634). Grade selection depends on design, service conditions and the mechanical properties required.
Dimensions follow ASME B18.2.1, tabulated on this page. ASTM A1082/A1082M sets chemistry (Table 1), heat treatment and mechanical properties (Tables 2 to 4) and marking (Table 5). ASTM A962/A962M general requirements also apply, and A1082 prevails where the two conflict (clause 4.1). Inch-pound units apply unless the order specifies A1082M (clause 1.4).
ISO 15156-3 Table A.24 accepts wrought duplex stainless steel for any equipment when it is solution-annealed and liquid-quenched or rapidly cooled, has 35 % to 65 % ferrite and has had no ageing heat treatment. With 30 ≤ PREN ≤ 40 and Mo ≥ 1.5 % the limit is 232 °C (450 °F) and 10 kPa (1.5 psi) H2S partial pressure; with 40 < PREN ≤ 45 it is 232 °C (450 °F) and 20 kPa (3 psi). Table A.27 accepts wrought 17-4 PH (S17400) at 33 HRC max after a double age at 620 °C (1150 °F) or a modified double age, for named wellhead, valve and subsurface components, up to 3.4 kPa (0.5 psi) H2S and pH 4.5 or above.
The grade symbol comes from Table 5 (clause 11.1), for example 32205 for S32205 or 174G for S17400 in H1150. With Supplementary Requirement S2 the marking goes on the heads of bolts of all sizes; if the area is too small, the grade symbol may go on one end and the manufacturer's identification on the other. Bolts under 1/4 in. [6 mm] are marked by agreement between purchaser and manufacturer.
Table 4: solution annealed at 1880 to 2060 °F [1025 to 1125 °C], water quenched. Up to and including 2 in.: tensile 116 ksi [800 MPa] and yield 80 ksi [550 MPa] min. Over 2 in.: 110 ksi [760 MPa] and 75 ksi [515 MPa] min. Elongation 15 % min and hardness 33 HRC or 310 HB max for both. The marking grade symbol is 32750 (Table 5).
