Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASME B18.2.2 Heavy Hex Nuts Dimensions
Wide-Profile Inch-Series Hex Nuts for Superior Load Distribution in High-Pressure Flange and Structural Bolting.
ASME B18.2.2 Heavy Hex Nuts are inch-series internally threaded fasteners with a significantly wider and taller profile compared to standard ASME B18.2.2 regular hex nuts — providing a larger bearing surface area that distributes bolt clamping load across a wider footprint, reducing surface pressure on the flange face and minimizing the risk of nut embedment into the joint material under high preload conditions, which makes them the standard nut type for heavy hex stud bolts and heavy hex bolts used in pipe flange assemblies, pressure vessel cover connections, structural steel joints, and heavy industrial equipment connections. The ASME B18.2.2 standard defines precise dimensional requirements for heavy hex nuts including width across flats, width across corners, nut thickness, chamfer, and thread specifications for nominal sizes from 1/4 inch through 4 inches, with the heavy hex nut's wider across-flats dimension clearly distinguished from the regular hex nut to prevent dimensional mismatch in wrench and socket selection during bolted joint assembly. When manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, ASME B18.2.2 Heavy Hex Nuts provide the combination of wide bearing surface, superior corrosion resistance, and maintained mechanical strength that is required for offshore oil and gas flange bolting, LNG terminal pressure equipment, desalination plant pipework, marine structural steelwork, and chemical process heat exchanger covers where both the heavy hex head geometry and stainless steel material performance are simultaneously mandated by the engineering design specification. In assemblies involving softer flange materials — such as aluminium alloy, fibre-reinforced plastic, or copper-nickel — the larger bearing area of the heavy hex nut is especially critical in preventing long-term embedment that would reduce bolt preload and lead to gasket leakage in service. ASTM A1082 heavy hex nuts are available with EN 10204 Type 3.1 material documentation for all quality-critical bolting procurement requirements.
ASME B18.2.2 Heavy Hex Nut Dimensions
| Nominal Size | Basic Major Diameter | Width Across Flats, F | Width Across Corners, G | Thickness, H | Maximum Runout of Bearing Surface to Thread Axis, FIM | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Basic | Min. | Max. | Min. | Max. | Basic | Min. | Max. | Up to 150k psi | 150k psi + | ||
| 1/4 | 0.2500 | 1/2 | 0.488 | 0.500 | 0.556 | 0.577 | 15/64 | 0.218 | 0.250 | 0.017 | 0.011 |
| 5/16 | 0.3125 | 9/16 | 0.546 | 0.562 | 0.622 | 0.650 | 19/64 | 0.280 | 0.314 | 0.020 | 0.012 |
| 3/8 | 0.3750 | 11/16 | 0.669 | 0.688 | 0.763 | 0.794 | 23/64 | 0.341 | 0.377 | 0.021 | 0.014 |
| 7/16 | 0.4375 | 3/4 | 0.728 | 0.750 | 0.830 | 0.866 | 27/64 | 0.403 | 0.441 | 0.022 | 0.015 |
| 1/2 | 0.5000 | 7/8 | 0.850 | 0.875 | 0.969 | 1.010 | 31/64 | 0.464 | 0.504 | 0.023 | 0.016 |
| 9/16 | 0.5625 | 15/16 | 0.909 | 0.938 | 1.037 | 1.083 | 35/64 | 0.526 | 0.568 | 0.024 | 0.017 |
| 5/8 | 0.6250 | 1 1/16 | 1.031 | 1.062 | 1.175 | 1.227 | 39/64 | 0.587 | 0.631 | 0.025 | 0.018 |
| 3/4 | 0.7500 | 1 1/4 | 1.212 | 1.250 | 1.382 | 1.443 | 47/64 | 0.710 | 0.758 | 0.027 | 0.020 |
| 7/8 | 0.8750 | 1 7/16 | 1.394 | 1.438 | 1.589 | 1.660 | 55/64 | 0.833 | 0.885 | 0.029 | 0.022 |
| 1 | 1.0000 | 1 5/8 | 1.575 | 1.625 | 1.796 | 1.876 | 63/64 | 0.956 | 1.012 | 0.031 | 0.024 |
| 1 1/8 | 1.1250 | 1 13/16 | 1.756 | 1.812 | 2.002 | 2.093 | 1 7/64 | 1.079 | 1.139 | 0.033 | 0.027 |
| 1 1/4 | 1.2500 | 2 | 1.938 | 2.000 | 2.209 | 2.309 | 1 7/32 | 1.187 | 1.251 | 0.035 | 0.030 |
| 1 3/8 | 1.3750 | 2 3/16 | 2.119 | 2.188 | 2.416 | 2.526 | 1 11/32 | 1.310 | 1.378 | 0.038 | 0.033 |
| 1 1/2 | 1.5000 | 2 3/8 | 2.300 | 2.375 | 2.622 | 2.742 | 1 15/32 | 1.433 | 1.505 | 0.041 | 0.036 |
| 1 5/8 | 1.6250 | 2 9/16 | 2.481 | 2.562 | 2.828 | 2.959 | 1 19/32 | 1.556 | 1.632 | 0.044 | 0.038 |
| 1 3/4 | 1.7500 | 2 3/4 | 2.662 | 2.750 | 3.035 | 3.175 | 1 23/32 | 1.679 | 1.759 | 0.048 | 0.041 |
| 1 7/8 | 1.8750 | 2 15/16 | 2.844 | 2.938 | 3.242 | 3.392 | 1 27/32 | 1.802 | 1.886 | 0.051 | 0.044 |
| 2 | 2.0000 | 3 1/8 | 3.025 | 3.125 | 3.449 | 3.608 | 1 31/32 | 1.925 | 2.013 | 0.055 | 0.047 |
| 2 1/4 | 2.2500 | 3 1/2 | 3.388 | 3.500 | 3.862 | 4.041 | 2 13/64 | 2.155 | 2.251 | 0.061 | 0.052 |
| 2 1/2 | 2.5000 | 3 7/8 | 3.750 | 3.875 | 4.275 | 4.474 | 2 29/64 | 2.401 | 2.505 | 0.068 | 0.058 |
| 2 3/4 | 2.7500 | 4 1/4 | 4.112 | 4.250 | 4.688 | 4.907 | 2 45/64 | 2.647 | 2.759 | 0.074 | 0.064 |
| 3 | 3.0000 | 4 5/8 | 4.475 | 4.625 | 5.102 | 5.340 | 2 61/64 | 2.893 | 3.013 | 0.081 | 0.070 |
| 3 1/4 | 3.2500 | 5 | 4.838 | 5.000 | 5.515 | 5.774 | 3 3/16 | 3.124 | 3.252 | 0.087 | 0.075 |
| 3 1/2 | 3.5000 | 5 3/8 | 5.200 | 5.375 | 5.928 | 6.207 | 3 7/16 | 3.370 | 3.506 | 0.094 | 0.081 |
| 3 3/4 | 3.7500 | 5 3/4 | 5.562 | 5.750 | 6.341 | 6.640 | 3 11/16 | 3.616 | 3.760 | 0.100 | 0.087 |
| 4 | 4.0000 | 6 1/8 | 5.925 | 6.125 | 6.755 | 7.073 | 3 15/16 | 3.862 | 4.014 | 0.107 | 0.093 |
Frequently Asked Questions
What stainless steel grades does ASTM A1082 cover for heavy hex nuts?
ASTM A1082 covers duplex grades (S31803/2205, S32205/2205, S32750/2507, S32760/Zeron 100, S39277/AL-6XN) and precipitation-hardening grades (S17400/17-4 PH, S17700/17-7 PH, S15700/15-7 PH, S35500/AM-355) - all available for this product family at TorqBolt.
What is the standard dimensional reference for these heavy hex nuts?
This product follows ASME B18.2 2, the dimensional standard for heavy hex nuts in stainless steel. Material chemistry, mechanical properties and heat treatment follow ASTM A1082/A1082M. TorqBolt supplies both inch-series and metric sizes per the applicable ASME or ISO drawing.
Are A1082 heavy hex nuts suitable for sour service (NACE MR0175)?
Yes, with hardness control. NACE MR0175 / ISO 15156 permits duplex grades S31803, S32205, S32750, S32760 at 28 HRC max for sour service. 17-4 PH (S17400) at H1150 condition (28 HRC) is the most common PH grade qualified for sour service. TorqBolt provides NACE-MR0175 compliant heat-treat reports.
What is the typical strength of A1082 super-duplex 2507 (S32750) heavy hex nuts?
Super-duplex 2507 (S32750) per A1082: tensile 116 ksi (800 MPa) min, yield 80 ksi (550 MPa) min, elongation 15% min, 32 HRC max. PREN ≈ 42 - suitable for seawater, brine and chloride-rich pressure-vessel service. Higher strength than austenitic A193 B8M while offering pitting resistance well above 304/316.
References & Standards
- ASTM A1082 / A1082M - Standard Specification for High-Strength Precipitation-Hardening and Duplex Stainless Steel Bolting for Special-Purpose Applications (current edition 2016, active)
- ASTM A962 / A962M - General Requirements for Special-Purpose Bolting Materials
- ASTM A370 - Mechanical Testing of Steel Products
- NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum & natural gas industries
- ASME B18 series - Dimensional standards for bolts, screws, nuts, studs
- ISO 4032 / 4033 / 4035 - Metric hexagon nut dimensional standards
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