RECOMMENDED DRILL SIZES FOR
SELF-TAPPING SCREWS (SHEET METAL)
| Self-Tapping Screw Size | Major Thread Diameter | Minor Thread Diameter | For Heavy Metals | For Light Metals | ||||||||
|
No. |
Threads per Inch |
O.D. |
Max. |
Mean | Min. |
Max.
|
Mean | Min. | Drill Size | Drill Size | ||
| 2 | 32 | .086 | .088 | .0850 | .082 | .064 | .0620 | .060 | 49 | .0730 | 49 | .0730 |
| 4 | 24 | .112 | .114 | .1110 | .108 | .086 | .0840 | .082 | 41 | .0960 | 41 | .0960 |
| 5 | 20 | .125 | .130 | .1265 | .123 | .094 | .0920 | .090 | 36 | .1065 | 36 | .1065 |
| 6 | 20 | .138 | .139 | .1355 | .132 | .104 | .1015 | .099 | 32 | .1160 | 32 | .1160 |
| 7 | 19 | .151 | .154 | .1505 | .147 | .115 | .1120 | .109 | 30 | .1285 | 30 | .1285 |
| 8 | 18 | .164 | .166 | .1625 | .159 | .122 | .1190 | .116 | 28 | .1405 | 29 | .1360 |
| 10 | 16 | .190 | .189 | .1855 | .182 | .141 | .1380 | .135 | 20 | .1610 | 21 | .1590 |
| 12 | 14 | .216 | .215 | .2115 | .208 | .164 | .1605 | .157 | 13 | .1850 | 14 | .1820 |
| 1/4 | 14 | .250 | .246 | .2415 | .237 | .192 | .1885 | .185 | 3 | .2130 | 4 | .2090 |
| 5/16 | 12 | .313 | .315 | .3105 | .306 | .244 | .2400 | .236 | I | .2720 | H | .2660 |
| 3/8 | 12 | .375 | .380 | .3755 | .371 | .309 | .3040 | .299 | R | .3390 | Q | .3320 |