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British Standard Fine (BSF) tapping drill sizes.
Ø = diameter
" = inch
TPI = threads per inch
| Tap Size | TPI | Tapping Drill Ømm |
Clearance drill Ømm |
|---|---|---|---|
| 3/16" | 32 | 3.95 | 4.90 |
| 7/32" | 28 | 4.63 | 5.70 |
| 1/4" | 26 | 5.35 | 6.50 |
| 9/32" | 26 | 6.10 | 7.4 |
| 5/16" | 22 | 6.75 | 8.1 |
| 3/8" | 20 | 8.22 | 9.70 |
| 7/16" | 18 | 9.6 | 11.30 |
| 1/2" | 16 | 11.1 | 13.0 |
| 9/16" | 16 | 12.70 | 14.50 |
| 5/8" | 14 | 14.00 | 16.25 |
| 11/16" | 14 | 15.60 | 17.75 |
| 3/4" | 12 | 16.9 | 19.25 |
| 7/8" | 11 | 19.85 | 22.50 |
| 1" | 10 | 22.75 | 25.75 |
| 1.1/8" | 9 | 25.7 | 29.0 |
| 1.1/4" | 9 | 28.80 | 32.0 |
| 1.3/8" | 8 | 31.60 | 35.50 |
| 1.1/2" | 8 | 34.80 | 38.50 |
BSF thread information.
BSF thread BS 84: 1956.
Developed by Joseph Whitworth in 1841 the thread has the same profile as the BSW thread, for use when a finer pitch was required.
The angle between the thread flanks is 55° and the thread has radii at both the roots and the crests of the thread.