British Standard Whitworth List of thread sizes Whitworth thread sizes

| Whitworth_size_in | Core_diameter_in | Threads_per_inch | Pitch_in | Tapping_drill_size_ |
|---|---|---|---|---|
| 1/16 | 0.0411 | 60 | 0.0167 | Number Drill 56 (1.2 mm) |
| 3/32 | 0.0672 | 48 | 0.0208 | Number Drill 49 (1.85 mm) |
| 1/8 | 0.0930 | 40 | 0.025 | Number Drill 39 (2.55 mm) |
| 5/32 | 0.1162 | 32 | 0.0313 | Number Drill 30 (3.2 mm) |
| 3/16 | 0.1341 | 24 | 0.0417 | Number Drill 26 (3.7 mm) |
| 7/32 | 0.1654 | 24 | 0.0417 | Number Drill 16 (4.5 mm) |
| 1/4 | 0.1860 | 20 | 0.05 | Number Drill 9 (5.1 mm) |
| 5/16 | 0.2414 | 18 | 0.0556 | Letter Drill F (6.5 mm) |
| 3/8 | 0.2950 | 16 | 0.0625 | 5/16 in (7.94 mm) |
| 7/16 | 0.3460 | 14 | 0.0714 | Letter Drill U (9.3 mm) |
| 1/2 | 0.3933 | 12 | 0.0833 | Letter Drill Z (10.5 mm) |