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 B18.31.2 Clamping Type Full Body Studs Dimension Standard
Inch-Series Full-Diameter Clamping Studs for High-Integrity Flange and Pressure Vessel Bolted Assemblies.
ASME B18.31.2 Clamping Type Full Body Studs are inch-series unheaded threaded fasteners featuring a continuous full-diameter unthreaded shank between threaded ends, engineered to provide predictable and uniform clamping load distribution in high-pressure pipe flange joints, heat exchangers, pressure vessels, and other critical bolted assemblies governed by ASME B16.5 and ASME PCC-1 gasketed joint standards. The standard defines all key dimensional parameters including body diameter, overall stud length, thread length on each end, thread pitch series — UNC, UNF, or 8UN — and all associated tolerances to ensure dimensional consistency and interchangeability across global supply chains. In demanding corrosion-resistant service environments, these studs are manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, delivering excellent resistance to chloride stress corrosion cracking, pitting corrosion, and crevice attack in offshore, marine, chemical, and food processing plant applications. The full-body design ensures that the stress cross-section is maintained at the full bolt diameter, minimizing stress concentration and improving fatigue performance under cyclic loading conditions typical in pressure piping systems. Always pair ASME B18.31.2 dimensional requirements with ASTM A1082 material specification for a complete and traceable engineering definition of full-body clamping stud bolts.
ASME B18.31.2 Dimensions for Clamping Type Full Body Studs (mm)
| Nominal Size |
Diameter, D | Nut End Minimum Full Thread Length, Bmin |
Minimum Body Diameter, DS | ||||
|---|---|---|---|---|---|---|---|
| L ≤ 254 mm (10 in) |
254 < L ≤ 406.4 mm (10 < L ≤ 16 in) |
L > 406.4 mm (16 in) |
UNC and NC-5 HF Threads |
UNF Threads |
8UN Threads |
||
| ¼ | 6.350 | 19.050 | 25.400 | 38.100 | 6.121 | 6.172 | … |
| 5/16 | 7.938 | 22.225 | 28.575 | 41.275 | 7.696 | 7.722 | … |
| 3/8 | 9.525 | 25.400 | 31.750 | 44.450 | 9.246 | 9.322 | … |
| 7/16 | 11.113 | 28.575 | 34.925 | 47.625 | 10.820 | 10.871 | … |
| ½ | 12.700 | 31.750 | 38.100 | 50.800 | 12.395 | 12.471 | … |
| 9/16 | 14.288 | 34.925 | 41.275 | 53.975 | 13.970 | 14.021 | … |
| 5/8 | 15.875 | 38.100 | 44.450 | 57.150 | 15.519 | 15.621 | … |
| ¾ | 19.050 | 44.450 | 50.800 | 63.500 | 18.669 | 18.771 | … |
| 7/8 | 22.225 | 50.800 | 57.150 | 69.850 | 21.819 | 21.920 | … |
| 1 | 25.400 | 57.150 | 63.500 | 76.200 | 24.968 | 25.070 | … |
| 1⅛ | 28.575 | 63.500 | 69.850 | 82.550 | 28.092 | 28.245 | 28.143 |
| 1¼ | 31.750 | 69.850 | 76.200 | 88.900 | 31.267 | 31.420 | 31.318 |
| 1⅜ | 34.925 | 76.200 | 82.550 | 95.250 | 34.392 | 34.595 | 34.493 |
| 1½ | 38.100 | 82.550 | 88.900 | 101.600 | 37.567 | 37.770 | 37.668 |
| 1⅝ | 41.275 | 88.900 | 95.250 | 107.950 | … | … | 40.843 |
| 1¾ | 44.450 | 95.250 | 101.600 | 114.300 | 43.866 | … | 44.018 |
| 1⅞ | 47.625 | 101.600 | 107.950 | 120.650 | … | … | 47.193 |
| 2 | 50.800 | 107.950 | 114.300 | 127.000 | 50.165 | … | 50.368 |
| 2¼ | 57.150 | 120.650 | 127.000 | 139.700 | 56.515 | … | 56.718 |
| 2½ | 63.500 | 133.350 | 139.700 | 152.400 | 62.814 | … | 63.068 |
| 2¾ | 69.850 | 146.050 | 152.400 | 165.100 | 69.164 | … | 69.418 |
| 3 | 76.200 | ... | 165.100 | 177.800 | 75.514 | … | 75.743 |
| 3¼ | 82.550 | ... | 177.800 | 190.500 | 81.864 | … | 82.093 |
| 3½ | 88.900 | ... | 190.500 | 203.200 | 88.214 | … | 88.443 |
| 3¾ | 95.250 | ... | 203.200 | 215.900 | 94.564 | … | 94.793 |
| 4 | 101.600 | ... | 215.900 | 228.600 | 100.914 | … | 101.143 |
ASME B18.31.2 Clamping Type Full Body Stud Length Tolerances (mm)
| Range, LT | Tolerance |
|---|---|
| From 19.05 through 63.5 | ±1.016 |
| Over 63.5 through 101.6 | ±2.032 |
| Over 101.6 through 203.2 | ±2.540 |
| Over 203.2 through 406.4 | ±3.048 |
| Over 406.4 | ±4.572 |
ASME B18.31.2 Dimensions for Clamping Type Full Body Studs (Inch)
| Nominal Size |
Diameter, D |
Nut End Minimum Full Thread Length, Bmin |
Minimum Body Diameter, DS | ||||
|---|---|---|---|---|---|---|---|
| L ≤ 10 | 10 < L ≤ 16 | L > 16 | UNC and NC-5 HF Threads |
UNF Threads |
8UN Threads |
||
| ¼ | 0.2500 | 0.750 | 1.000 | 1.500 | 0.241 | 0.243 | … |
| 5/16 | 0.3125 | 0.875 | 1.125 | 1.625 | 0.303 | 0.304 | … |
| 3/8 | 0.3750 | 1.000 | 1.250 | 1.750 | 0.364 | 0.367 | … |
| 7/16 | 0.4375 | 1.125 | 1.375 | 1.875 | 0.426 | 0.428 | … |
| ½ | 0.5000 | 1.250 | 1.500 | 2.000 | 0.488 | 0.491 | … |
| 9/16 | 0.5625 | 1.375 | 1.625 | 2.125 | 0.550 | 0.552 | … |
| 5/8 | 0.6250 | 1.500 | 1.750 | 2.250 | 0.611 | 0.615 | … |
| ¾ | 0.7500 | 1.750 | 2.000 | 2.500 | 0.735 | 0.739 | … |
| 7/8 | 0.8750 | 2.000 | 2.250 | 2.750 | 0.859 | 0.863 | … |
| 1 | 1.0000 | 2.250 | 2.500 | 3.000 | 0.983 | 0.987 | … |
| 1⅛ | 1.1250 | 2.500 | 2.750 | 3.250 | 1.106 | 1.112 | 1.108 |
| 1¼ | 1.2500 | 2.750 | 3.000 | 3.500 | 1.231 | 1.237 | 1.233 |
| 1⅜ | 1.3750 | 3.000 | 3.250 | 3.750 | 1.354 | 1.362 | 1.358 |
| 1½ | 1.5000 | 3.250 | 3.500 | 4.000 | 1.479 | 1.487 | 1.483 |
| 1⅝ | 1.6250 | 3.500 | 3.750 | 4.250 | … | … | 1.608 |
| 1¾ | 1.7500 | 3.750 | 4.000 | 4.500 | 1.727 | … | 1.733 |
| 1⅞ | 1.8750 | 4.000 | 4.250 | 4.750 | … | … | 1.858 |
| 2 | 2.0000 | 4.250 | 4.500 | 5.000 | 1.975 | … | 1.983 |
| 2¼ | 2.2500 | 4.750 | 5.000 | 5.500 | 2.225 | … | 2.233 |
| 2½ | 2.5000 | 5.250 | 5.500 | 6.000 | 2.473 | … | 2.483 |
| 2¾ | 2.7500 | 5.750 | 6.000 | 6.500 | 2.723 | … | 2.733 |
| 3 | 3.0000 | ... | 6.500 | 7.000 | 2.973 | … | 2.982 |
| 3¼ | 3.2500 | ... | 7.000 | 7.500 | 3.223 | … | 3.232 |
| 3½ | 3.5000 | ... | 7.500 | 8.000 | 3.473 | … | 3.482 |
| 3¾ | 3.7500 | ... | 8.000 | 8.500 | 3.723 | … | 3.732 |
| 4 | 4.0000 | ... | 8.500 | 9.000 | 3.973 | … | 3.982 |
ASME B18.31.2 Clamping Type Full Body Stud Length Tolerances (Inch)
| Range, LT | Tolerance |
|---|---|
| From ¾ through 2½ | ±0.04 |
| Over 2½ through 4 | ±0.08 |
| Over 4 through 8 | ±0.10 |
| Over 8 through 16 | ±0.12 |
| Over 16 | ±0.18 |
Frequently Asked Questions
What stainless steel grades does ASTM A1082 cover for stud bolts?
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 stud bolts?
This product follows ASME B18.31 2, the dimensional standard for stud bolts 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 stud bolts 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) stud bolts?
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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