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    2. ASME B18.2.3.5M Metric Hex Bolts

    ASME B18.2.3.5M Metric Hex Bolts Dimension Standard

    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 the complete range of metric bolt sizes — 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.

    ASME B18.2.3.5M Hex Bolts

    ASME B18.2.3.5m Hex Bolts Dimensions

    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
    • a Basic thread length, B, is a reference dimension.
    • b Thissize with width across flats of 15 mm is not standard. Unless specifically ordered, M10 hex
    • bolts with 16 mm width across flats will be furnished.
    • All dimensions are in millimeters.

    Frequently Asked Questions

    What stainless steel grades does ASTM A1082 cover for hex 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 hex bolts?

    This product follows ASME B18.2 3 5M, the dimensional standard for hex 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 hex 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) hex 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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