Number Drills
This system of numbering drills is no longer used, but may be of use in deciphering old drawings.
| No. | Diameter inches | No. | Diameter inches | No. | Diameter inches | No. | Diameter inches |
| 1 | 0.228 | 21 | 0.159 | 41 | 0.096 | 61 | 0.039 |
| 2 | 0.221 | 22 | 0.157 | 42 | 0.0935 | 62 | 0.038 |
| 3 | 0.213 | 23 | 0.154 | 43 | 0.089 | 63 | 0.037 |
| 4 | 0.209 | 24 | 0.152 | 44 | 0.086 | 64 | 0.036 |
| 5 | 0.2055 | 25 | 0.1495 | 45 | 0.082 | 65 | 0.035 |
| 6 | 0.204 | 26 | 0.147 | 46 | 0.081 | 66 | 0.033 |
| 7 | 0.201 | 27 | 0.144 | 47 | 0.0785 | 67 | 0.032 |
| 8 | 0.199 | 28 | 0.1405 | 48 | 0.076 | 68 | 0.031 |
| 9 | 0.196 | 29 | 0.136 | 49 | 0.073 | 69 | 0.0292 |
| 10 | 0.1935 | 30 | 0.1285 | 50 | 0.070 | 70 | 0.028 |
| 11 | 0.191 | 31 | 0.120 | 51 | 0.067 | 71 | 0.026 |
| 12 | 0.189 | 32 | 0.116 | 52 | 0.0635 | 72 | 0.025 |
| 13 | 0.185 | 33 | 0.113 | 53 | 0.0595 | 73 | 0.024 |
| 14 | 0.182 | 34 | 0.111 | 54 | 0.055 | 74 | 0.0225 |
| 15 | 0.180 | 35 | 0.110 | 55 | 0.052 | 75 | 0.021 |
| 16 | 0.177 | 36 | 0.1065 | 56 | 0.0465 | 76 | 0.020 |
| 17 | 0.173 | 37 | 0.104 | 57 | 0.043 | 77 | 0.018 |
| 18 | 0.1695 | 38 | 0.1015 | 58 | 0.042 | 78 | 0.016 |
| 19 | 0.166 | 39 | 0.0995 | 59 | 0.041 | 79 | 0.0145 |
| 20 | 0.161 | 40 | 0.098 | 60 | 0.040 | 80 | 0.0135 |
See also: Drill Bits, Letter Drills.
Subjects: Tools


