Short Run Pro - Manufacturer of metal parts, custom metal brackets and custom metal fabrication services provider.
  • Countersinking Sizes

  • Countersinks

    Countersinking Holes Service

    A countersink is a tapered hole drilled with a wide outer portion. A common usage is to allow the head of a countersunk bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material.

    Unless otherwise specified, countersink to a diameter 0.10-.015" larger than the basic size of the thread. 80 (or 82) degree and 100 degree counter sinks are most common for flat head screws.



    Proper hole size and countersink size for screws.

    Table for 82 Degree Countersink

    Screw Size #4 #5 #6 #8 #10 #12 1/4-20
    Max Head Dia. 0.225 0.252 0.279 0.332 0.385 0.438 0.507
    Min Head Dia. 0.207 0.232 0.257 0.308 0.359 0.410 0.477
    Top Ctsk Dia. 0.216 0.242 0.268 0.320 0.372 0.424 0.492
    Body Dia. 0.112 0.125 0.138 0.164 0.190 0.216 0.250

    Hole sizes before countersinking for 82 degree Screws (+/- .005)

    Screw Size #4 #5 #6 #8 #10 #12 1/4-20
    Thickness
    0.020 0.1950 0.2220 0.2490 0.3020 0.3550 0.4060 0.4770
    .025 0.1870 0.2130 0.2400 0.2930 0.3460 0.4060 0.4680
    0.030 0.1760 0.2010 0.2280 0.2810 0.3340 0.4060 0.4560
    0.035 0.1660 0.1960 0.2210 0.2740 0.3280 0.4060 0.4490
    0.042 0.1600 0.1870 0.2130 0.2630 0.3170 0.4060 0.4370
    0.050 0.1410 0.1700 0.1960 0.2500 0.3030 0.3830 0.4240
    0.060 0.1280 0.1520 0.1790 0.2320 0.2850 0.3830 0.4060
    0.074 0.1250 0.1280 0.1560 0.2080 0.2630 0.3680 0.3830
    0.090 0.1250 0.1280 0.1560 0.1940 0.2500 0.3360 0.3680
    0.120 0.1250 0.1280 0.1560 0.1870 0.2130 0.3030 0.3120
    0.179 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
    0.250 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120




  • Table for 100 Degree Countersink

    Screw Size #4 #5 #6 #8 #10 #12 1/4-20
    Max Head Dia. 0.231 0.257 0.283 0.335 0.387 0.439 0.507
    Min Head Dia. 0.201 0.227 0.253 0.305 0.357 0.409 0.477
    Top Ctsk Dia. 0.216 0.242 0.268 0.320 0.372 0.424 0.492
    Body Dia. 0.112 0.125 0.138 0.164 0.190 0.216 0.250

    Hole sizes before countersinking for 100 degree Screws (+/- .005)

    Screw Size #4 #5 #6 #8 #10 #12 1/4-20
    Thickness
    0.020 0.1870 0.2130 0.2490 0.3020 0.3460 0.4060 0.4770
    .025 0.1870 0.2130 0.2320 0.2930 0.3460 0.4060 0.4680
    0.030 0.1760 0.1960 0.2210 0.2740 0.3360 0.3830 0.4560
    0.035 0.1600 0.1870 0.2130 0.2630 0.312 0.3680 0.4370
    0.042 0.1410 0.1760 0.2960 0.2500 0.3130 0.4680 0.4240
    0.050 0.1250 0.1280 0.1760 0.2320 0.2850 0.3360 0.4640
    0.060 0.1250 0.1280 0.1560 0.2130 0.2850 0.3830 0.4060
    0.074 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
    0.090 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
    0.120 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
    0.179 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
    0.250 0.1250 0.1280 0.1560 0.1870 0.2130 0.2320 0.3120
DD
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