• View PDF
    Standard
  •   0091-22-66157017
  •   info@torqbolt.com
    • Home
    2. B18.2.1 Hex Cap Screws

    ASME B18.2.1 Hex Cap Screws – Dimensions, Specifications & Standards

    Dimensions & Tolerances for Hex Cap Screws in Industrial Applications.

    ASME B18.2.1 Hex Cap Screws are inch-series headed fasteners manufactured to precise dimensional requirements under the American National Standard, covering head height, width across flats, body diameter, thread length, washer face thickness, and bearing surface angularity. These screws are commonly used in bolted connections requiring tight tolerances and consistent clamping loads across mechanical, structural, and process piping assemblies. They are widely specified with ASTM A1014/A1014M for UNS N07718 (Inconel 718) bolting, providing exceptional high-temperature strength and corrosion resistance for oil and gas, aerospace, and chemical processing. Also available in ASTM A449, A354, A193, A307, and stainless steel F593 grades. Dimensional compliance is governed by ASME B18.2.1, while strength and chemistry are defined by the paired ASTM specification.

    ASME B18.2.1 Hex Cap Screws

    ASME B18.2.1 Hex Cap Screws Dimensions (mm)

    Nominal Size or Basic Product Diameter Body Diameter, E Width Across Flats, F Width Across Corners, G Head Height, H Minimum Wrenching Height, J Nominal Thread Length for Screw Lengths, LT Transition Thread Length, Y
    Reference    		 Maximum Total Runout of Bearing Surface FIM
    Max. Min. Basic Max. Min. Max. Min. Basic Max. Min. 150mm (6") and Shorter Over 150mm (6")
    1/4 0.2500 6.350 6.223 11.113 11.125 10.871 12.827 12.395 3.969 4.140 3.810 2.692 19.050 25.400 6.350 0.254
    5/16 0.3125 7.938 7.785 12.700 12.700 12.421 14.656 14.148 5.159 5.359 4.953 3.556 22.225 28.575 7.061 0.279
    3/8 0.3750 9.525 9.373 14.288 14.275 13.995 16.510 15.951 5.953 6.172 5.740 4.064 25.400 31.750 7.925 0.305
    7/16 0.4375 11.113 10.935 15.875 15.875 15.545 18.339 17.729 7.144 7.391 6.909 4.953 28.575 34.925 9.068 0.330
    1/2 0.5000 12.700 12.522 19.050 19.050 18.694 21.996 21.336 7.938 8.204 7.671 5.461 31.750 38.100 9.779 0.356
    9/16 0.5625 14.288 14.084 20.638 20.625 20.269 23.825 23.114 9.128 9.423 8.839 6.350 34.925 41.275 10.592 0.381
    5/8 0.6250 15.875 15.672 23.813 23.825 23.419 27.508 26.695 9.922 10.236 9.601 6.833 38.100 44.450 11.557 0.432
    3/4 0.7500 19.050 18.821 28.575 28.575 27.940 32.995 31.852 11.906 12.268 11.557 8.230 44.450 50.800 12.700 0.508
    7/8 0.8750 22.225 21.996 33.338 33.325 32.639 38.506 37.211 13.891 14.300 13.487 9.601 50.800 57.150 14.122 0.584
    1 1.0000 25.400 25.146 38.100 38.100 37.313 43.993 42.545 15.478 15.926 15.011 10.566 57.150 63.500 15.875 0.660
    1 1/8 1.1250 28.575 28.296 42.863 42.875 41.427 49.505 47.219 17.463 18.237 16.713 11.709 63.500 69.850 18.136 0.737
    1 1/4 1.2500 31.750 31.471 47.625 47.625 46.025 54.991 52.476 19.844 20.650 19.025 13.462 69.850 76.200 18.136 0.838
    1 3/8 1.3750 34.925 34.620 52.388 52.375 50.648 60.503 57.734 21.431 22.301 20.574 14.453 76.200 82.550 21.158 0.914
    1 1/2 1.5000 38.100 37.795 57.150 57.150 55.245 65.989 62.992 23.813 24.740 22.911 16.256 82.550 88.900 21.158 0.991
    1 5/8 1.6250 41.275 40.970 61.913 61.925 59.842 71.501 68.224 25.400 26.365 24.435 17.628 88.900 95.250 23.089 1.092
    1 3/4 1.7500 44.450 44.145 66.675 66.675 64.465 76.987 73.482 27.781 28.804 26.772 18.999 95.250 101.600 25.400 1.168
    1 7/8 1.8750 47.625 47.320 71.438 71.425 69.063 82.499 78.715 29.369 30.429 28.296 20.371 101.600 107.950 25.400 1.245
    2 2.0000 50.800 50.495 76.200 76.200 73.660 87.986 83.972 30.956 32.080 29.845 20.955 107.950 114.300 28.219 1.321
    2 1/4 2.2500 57.150 56.845 85.725 85.725 82.855 98.984 94.463 34.925 36.144 33.706 23.698 ... 127.000 28.219 1.499
    2 1/2 2.5000 63.500 63.195 95.250 95.250 92.075 109.982 104.978 40.481 40.208 37.567 26.467 ... 139.700 31.750 1.651
    2 3/4 2.7500 69.850 69.545 104.775 104.775 101.295 120.980 115.468 42.863 44.298 41.453 29.235 ... 152.400 31.750 1.829
    3 3.0000 76.200 75.895 114.300 114.300 110.490 131.978 125.959 47.625 49.149 46.101 32.766 ... 165.100 31.750 2.007

    ASME B18.2.1 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
    Related Specifications
    Surface Treatments
    Certifications
    About Us
    Questions? Contact us.
    Showcase of our Microsites.
    Satisfaction Survey

    survey

    TUVRheinland CRETIFIED

    © TorqBolt P(Ltd) · Built with in INDIA.