British Standard Whitworth Coarse Thread Series (parallel, cylindrical) In GB most common Thread. Corresponds to the Metric Thread in its type of use.
| Nominal Diameter |
Major Diameter Inch |
Major Diameter mm |
Tapping Drill Size mm |
TPI | Pitch mm |
| W 1/16″ | 1/16 | 1.588 | 1.05 | 60 | 0.423 |
| W 3/32″ | 3/32 | 2.381 | 1.70 | 48 | 0.529 |
| W 1/8″ | 1/8 | 3.175 | 2.36 | 40 | 0.635 |
| W 5/32″ | 5/32 | 3.969 | 2.95 | 32 | 0.794 |
| W 3/16″ | 3/16 | 4.763 | 3.41 | 24 | 1.058 |
| W 7/32″ | 7/32 | 5.556 | 4.20 | 24 | 1.058 |
| W 1/4″ | 1/4 | 6.350 | 4.72 | 20 | 1.270 |
| W 5/16″ | 5/16 | 7.940 | 6.13 | 18 | 1.411 |
| W 3/8″ | 3/8 | 9.525 | 7.49 | 16 | 1.587 |
| W 7/16″ | 7/16 | 11.113 | 8.79 | 14 | 1.814 |
| W 1/2″ | 1/2 | 12.700 | 9.99 | 12 | 2.117 |
| W 9/16″ | 9/16 | 14.288 | 11.58 | 12 | 2.117 |
| W 5/8″ | 5/8 | 15.875 | 12.92 | 11 | 2.309 |
| W 3/4″ | 3/4 | 19.050 | 15.80 | 10 | 2.540 |
| W 7/8″ | 7/8 | 22.225 | 18.61 | 9 | 2.822 |
| W 1″ | 1 | 25.400 | 21.34 | 8 | 3.175 |
| W 1 1/8″ | 1 1/8 | 28.575 | 23.93 | 7 | 3.628 |
| W 1 1/4″ | 1 1/4 | 31.750 | 27.11 | 7 | 3.628 |
| W 1 3/8″ | 1 3/8 | 34.925 | 29.51 | 6 | 4.233 |
| W 1 1/2″ | 1 1/2 | 38.100 | 32.68 | 6 | 4.233 |
| W 1 5/8″ | 1 5/8 | 41.275 | 34.77 | 5 | 5.080 |
| W 1 3/4″ | 1 3/4 | 44.450 | 37.95 | 5 | 5.080 |
| W 1 7/8″ | 1 7/8 | 47.625 | 40.40 | 4.5 | 5.644 |
| W 2″ | 2 | 50.800 | 43.58 | 4.5 | 5.644 |
| W 2 1/4″ | 2 1/2 | 57.150 | 49.02 | 4 | 6.350 |
| W 2 1/2″ | 2 1/2 | 63.500 | 55.37 | 4 | 6.350 |
| W 2 3/4″ | 2 3/4 | 69.850 | 60.56 | 3.5 | 7.257 |
| W 3 “ | 3 | 76.200 | 66.91 | 3.5 | 7.257 |
| W 3 1/4″ | 3 1/4 | 82.550 | 72.55 | 3.25 | 7.815 |
| W 3 1/2″ | 3 1/2 | 88.900 | 78.90 | 3.25 | 7.815 |
| W 3 3/4″ | 3 3/4 | 95.250 | 84.41 | 3 | 8.467 |
| W 4″ | 4 | 101.600 | 90.76 | 3 | 8.467 |