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    2. ASME B18.2.1 Heavy Hex Cap Screws

    ASME B18.2.1 Heavy Hex Cap Screws Dimension Standard

    Robust Inch-Series Cap Screws with Washer Face and Wide Heavy Hex Head for High-Load Process and Industrial Service.

    ASME B18.2.1 Heavy Hex Cap Screws are inch-series threaded fasteners that combine the precise dimensional accuracy and washer-face bearing surface of a cap screw with the wider and taller hexagonal head profile of a heavy hex configuration — delivering superior clamping area, enhanced torque resistance, and improved load distribution compared to standard hex cap screws in heavy-duty mechanical, structural, and process equipment assemblies. The standard defines precise dimensional requirements for head height, width across flats, body diameter, thread length, washer face thickness, bearing surface angularity, and underhead fillet radii for heavy hex cap screws up to 6 inches in diameter, ensuring tight interchangeability across manufacturers. In demanding service environments, these cap screws are manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, which provides excellent corrosion resistance, sustained mechanical properties at elevated temperatures, and reliable performance in aggressive chemical and marine environments. They are particularly well-suited for pharmaceutical processing equipment, food-grade machinery, chemical reactors, and offshore structural assemblies where both strength and corrosion resistance are simultaneously critical. All heavy hex cap screws must comply with ASME B18.2.1 dimensional requirements while being independently assessed for mechanical and chemical properties per the ASTM A1082 material specification.

    ASME B18.2.1 Heavy Hex Cap Screws

    ASME B18.2.1 Heavy Hex Cap Screws Dimensions (mm)

    Nominal Size Body Diameter, E Width Across Flats, F Width Across Corners, G Head Height, H Minimum Wrenching Height, J Thread Length, LT Transition Thread Length, Y Maximum Total Runout of Bearing Surface FIM
    Max. Min. Basic Max. Min. Max. Min. Basic Max. Min. >6" <6" Reference
    3⁄8 9.53 9.53 9.14 17.46 17.48 16.99 20.17 19.38 5.95 6.17 5.74 4.06 25.40 31.75 7.92 0.36
    1⁄2 12.70 12.70 12.24 22.23 22.23 21.59 25.65 24.61 7.94 8.20 7.67 5.46 31.75 38.10 9.78 0.41
    5⁄8 15.88 15.88 15.37 26.99 26.97 26.19 31.17 29.85 9.92 10.24 9.60 6.83 38.10 44.45 11.56 0.48
    3⁄4 19.05 19.05 18.52 31.75 31.75 30.78 36.65 35.13 11.91 12.27 11.56 8.23 44.45 50.80 12.70 0.56
    7⁄8 22.23 22.23 21.64 36.51 36.53 35.41 42.16 40.36 13.89 14.30 13.49 9.60 50.80 57.15 14.12 0.64
    1 25.40 25.40 24.79 41.28 41.28 40.01 47.65 45.62 15.48 15.93 15.01 10.57 57.15 63.50 15.88 0.71
    1 1⁄8 28.58 28.58 27.89 46.04 46.02 44.60 53.16 50.85 17.46 18.24 16.71 11.71 63.50 69.85 18.14 0.81
    1 1⁄4 31.75 31.75 31.06 50.80 50.80 49.23 58.65 56.11 19.84 20.65 19.02 13.46 69.85 76.20 18.14 0.89
    1 3⁄8 34.93 34.93 34.16 55.56 55.58 53.82 64.16 61.37 21.43 22.30 20.57 14.45 76.20 82.55 21.16 0.97
    1 1⁄2 38.10 38.10 37.34 60.33 60.33 58.42 69.65 66.60 23.81 24.74 22.91 16.26 82.55 88.90 21.16 1.04
    1 5⁄8 41.28 41.28 40.41 65.09 65.07 63.02 75.16 71.86 25.40 26.37 24.43 17.63 88.90 95.25 23.09 1.12
    1 3⁄4 44.45 44.45 43.59 69.85 69.85 67.61 80.65 77.09 27.78 28.80 26.77 19.00 95.25 101.60 25.40 1.22
    1 7⁄8 47.63 47.63 46.71 74.61 74.63 72.24 86.16 82.35 29.37 30.43 28.30 20.37 101.60 107.95 25.40 1.32
    2 50.80 50.80 49.89 79.38 79.38 76.84 91.64 87.60 30.96 32.08 29.85 20.96 107.95 114.30 28.22 1.40
    2 1⁄4 57.15 57.15 56.24 88.90 88.90 86.06 102.64 98.09 34.93 36.14 33.71 23.70 ... 127.00 28.22 1.55
    2 1⁄2 63.50 63.50 62.51 98.43 98.43 95.25 113.64 108.59 30.96 40.21 37.57 26.47 ... 139.70 31.75 1.73
    2 3⁄4 69.85 69.85 68.86 107.95 107.95 104.44 124.64 119.08 26.99 44.30 41.45 29.24 ... 152.40 31.75 1.88
    3 76.20 76.20 75.21 117.48 117.48 113.67 135.64 129.59 47.63 49.15 46.10 32.77 ... 165.10 31.75 2.06
    3 1⁄4 82.55 82.55 81.53 127.00 127.00 122.89 146.66 140.08 50.80 54.00 50.75 35.53 ... 177.80 31.75 2.31
    3 1⁄2 88.90 88.90 87.91 136.53 136.53 132.08 157.66 150.57 57.15 57.30 53.85 37.69 ... 190.50 31.75 2.49
    3 3⁄4 95.25 95.25 94.26 146.05 146.05 141.27 168.66 161.06 60.33 62.15 58.50 40.94 ... 203.20 31.75 2.67
    4 101.60 101.60 100.61 155.58 155.58 150.50 179.65 171.58 63.50 65.43 61.57 43.10 ... 215.90 31.75 2.84
    4 1⁄4 107.95 107.95 107.26 165.10 165.10 159.72 190.65 182.07 69.85 70.31 66.24 46.38 ... 228.60 31.75 3.02
    4 1⁄2 114.30 114.30 113.61 174.63 174.63 168.91 201.65 192.56 73.03 73.56 69.29 48.51 ... 241.30 31.75 3.20
    4 3⁄4 120.65 120.65 119.96 184.15 184.15 178.10 212.65 203.05 76.20 78.44 73.96 51.77 ... 254.00 31.75 3.38
    5 127.00 127.00 126.30 193.68 193.68 187.33 223.65 213.56 79.38 81.71 77.04 53.92 ... 266.70 31.75 3.56
    5 1⁄4 133.35 133.35 132.65 203.20 203.20 196.55 234.65 224.05 85.73 86.56 81.69 57.18 ... 279.40 31.75 3.73
    5 1⁄2 139.70 139.70 139.00 212.73 212.73 205.74 245.64 234.54 88.90 89.87 84.79 59.36 ... 292.10 31.75 3.91
    5 3⁄4 146.05 146.05 145.35 222.25 222.25 214.93 256.64 245.03 92.08 94.72 89.43 62.61 ... 304.80 31.75 4.09
    6 152.40 152.40 151.70 231.78 231.78 224.16 267.64 255.52 95.25 97.99 92.51 64.74 ... 317.50 31.75 4.27
    • GENERAL NOTES:
      • (a) Wrenching Height, J. Wrenching height is a distance measured from the bearing surface up the side of the head at the corners. The width across corners shall be within specified limits for the full wrenching height.
      • (b) Refer to section 4 for further information.

    ASME B18.2.1 Heavy Hex Cap Screws Length Tolerance (mm)

    Nominal Length Nominal Size (inches)
    1/4 to 3/8 7/16 and 1/2 9/16 to 3/4 7/8 and 1 1 1/8 to 1 1/2 Over 1 1/2
    Up to 25.4 mm, incl. +0.000
    0.762    		 +0.000
    0.762    		 +0.000
    0.762    		 ... ... ...
    Over 25.4 mm to 63.5 mm, incl. +0.000
    1.016    		 +0.000
    1.524    		 +0.000
    2.032    		 +0.000
    2.540    		 +0.000
    3.048    		 +0.000
    4.572
    Over 63.5 mm to 101.6 mm, incl. +0.000
    1.524    		 +0.000
    2.032    		 +0.000
    2.540    		 +0.000
    3.556    		 +0.000
    4.064    		 +0.000
    5.080
    Over 101.6 mm to 152.4 mm, incl. +0.000
    2.540    		 +0.000
    2.540    		 +0.000
    2.540    		 +0.000
    4.064    		 +0.000
    4.572    		 +0.000
    5.588
    Longer than 152.4 mm +0.000
    4.572    		 +0.000
    4.572    		 +0.000
    4.572    		 +0.000
    5.080    		 +0.000
    5.588    		 +0.000
    6.096

    Frequently Asked Questions

    What stainless steel grades does ASTM A1082 cover for din 6914?

    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 din 6914?

    This product follows ASME B18.2 1, the dimensional standard for din 6914 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 din 6914 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) din 6914?

    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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