Countersunk Holes
A countersink is a tapered hole drilled with a wide outer portion. A common usage of the countersunk hole is to allow the head of a flat head bolt or screw, when placed in the hole, to sit flush with or below the surface of the surrounding material. A Countersunk Hole is made with use of a drill bit and treating a laser cut hole with the bit to taper out the countersink.
Unless otherwise specified, countersunk holes are of a diameter 0.10-.015" larger than the basic size of the laser hole at . 80 (or 82) degree and 100 degree countersinks 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 Countersunk 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 Countersunk 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 |
