Globally Recognized Metric Hex Bolt Dimensional Standard for Structural, Pressure, and Industrial Applications.
ASME B18.2.3.5M Metric Hex Bolts are metric-series externally threaded fasteners governed by comprehensive dimensional requirements expressed in SI units, covering head height, width across flats, width across corners, body diameter, thread pitch, thread length, and bolt length tolerances for metric bolt sizes M5 through M100, making them the standard dimensional reference for metric hex bolting in North American-designed systems that interface with international equipment, global supply chains, and projects governed by metric engineering codes. The ASME B18.2.3.5M standard ensures dimensional interchangeability between metric hex bolt suppliers across different countries, which is essential for large international projects procuring fasteners from multiple global manufacturers simultaneously. In corrosion-resistant service applications, these metric hex bolts are manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, which provides excellent corrosion resistance, high tensile strength, and long service life required in offshore oil and gas equipment, LNG terminals, desalination plants, marine port structures, and chemical process facilities. ASTM A1082 stainless steel metric hex bolts are fully compatible with ISO metric hex nuts per ISO 4032 and ISO 4033, providing complete corrosion-resistant bolted assemblies in matched stainless steel grades. All lots are available with EN 10204 Type 3.1 material test certificates for full traceability and quality assurance.
| Nominal Dia., D and Thread Pitch | Body Diameter, Ds | Width Across Flats, S | Width Across Corners, E | Head Height, K | Wrenching Height, K1 | For Bolt Lengths | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| < 125 mm | > 125 and < 200 mm | > 200 mm | ||||||||||
| Max | Min | Max | Min | Max | Min | Max | Min | Min | Basic Thread Length, a B | |||
| M5 × 0.8 | 5.48 | 4.52 | 8 | 7.64 | 9.24 | 8.63 | 3.58 | 3.35 | 2.4 | 16 | 22 | 35 |
| M6 × 1 | 6.19 | 5.52 | 10 | 9.64 | 11.55 | 10.89 | 4.38 | 3.55 | 2.8 | 18 | 24 | 37 |
| M8 × 1.25 | 8.58 | 7.42 | 13 | 12.57 | 15.01 | 14.2 | 5.68 | 5.1 | 3.7 | 22 | 28 | 41 |
| M10 × 1.5 | 10.58 | 9.42 | 15 | 14.57 | 17.32 | 16.46 | 6.85 | 6.17 | 4.5 | 26 | 32 | 45 |
| M10 × 1.5 | 10.58 | 9.42 | 16 | 15.57 | 18.48 | 17.59 | 6.85 | 6.17 | 4.5 | 26 | 32 | 45 |
| M12 × 1.75 | 12.7 | 11.3 | 18 | 17.57 | 20.78 | 19.85 | 7.95 | 7.24 | 5.2 | 30 | 36 | 49 |
| M14 × 2 | 14.7 | 13.3 | 21 | 20.16 | 24.25 | 22.78 | 9.25 | 8.51 | 6.2 | 34 | 40 | 53 |
| M16 × 2 | 16.7 | 15.3 | 24 | 23.16 | 27.71 | 26.17 | 10.75 | 9.68 | 7 | 38 | 44 | 57 |
| M20 × 2.5 | 20.84 | 19.16 | 30 | 29.16 | 34.64 | 32.95 | 13.4 | 12.12 | 8.8 | 46 | 52 | 65 |
| M24 × 3 | 24.84 | 23.16 | 36 | 35 | 41.57 | 39.55 | 15.9 | 14.56 | 10.5 | 54 | 60 | 73 |
| M30 × 3.5 | 30.84 | 29.16 | 46 | 45 | 53.12 | 50.55 | 19.75 | 17.92 | 13.1 | 66 | 72 | 85 |
| M36 × 4 | 37 | 35 | 55 | 53.8 | 63.51 | 60.79 | 23.55 | 21.72 | 15.8 | 78 | 84 | 97 |
| M42 × 4.5 | 43 | 41 | 65 | 62.9 | 75.06 | 71.71 | 27.05 | 25.03 | 18.2 | 90 | 96 | 109 |
| M48 × 5 | 49 | 47 | 75 | 72.6 | 86.6 | 82.76 | 31.07 | 28.93 | 21 | 102 | 108 | 121 |
| M56 × 5.5 | 57.2 | 54.8 | 85 | 82.2 | 98.15 | 93.71 | 36.2 | 33.8 | 24.5 | ... | 124 | 137 |
| M64 × 6 | 65.52 | 62.8 | 95 | 91.8 | 109.7 | 104.65 | 41.32 | 38.68 | 28 | ... | 140 | 153 |
| M72 × 6 | 73.84 | 70.8 | 105 | 101.4 | 121.24 | 115.6 | 46.45 | 43.55 | 31.5 | ... | 156 | 169 |
| M80 × 6 | 82.16 | 78.8 | 115 | 111 | 132.79 | 126.54 | 51.58 | 48.42 | 35 | ... | 172 | 185 |
| M90 × 6 | 92.48 | 88.6 | 130 | 125.5 | 150.11 | 143.07 | 57.74 | 54.26 | 39.2 | ... | 192 | 205 |
| M100 × 6 | 102.8 | 98.6 | 145 | 140 | 167.43 | 159.6 | 63.9 | 60.1 | 43.4 | ... | 212 | 225 |
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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 B18.2.3.5M, 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).
