The British Standard Whitworth (BSW) thread system is commonly used in the United Kingdom for various applications. It features a 55-degree thread angle and rounded peaks and valleys. The thread data chart below provides common thread sizes and their corresponding thread pitch, major diameter, minor diameter, pitch diameter, and tapping drill size.
| SIZE | TPI | EXTERNAL | INTERNAL | DRILL SIZE | DRILL SIZE | ||||
| BSW 55 | MAJORS | MINORS | CLEARANCE HOLE | TAPPED HOLE | |||||
| INCH | MM | INCH | MM | INCH | MM | INCH | MM | ||
| 1/16 | 60 | 0.0620 | 1.59 | 0.0410 | 1.05 | 1.99 | 1.15 | ||
| 3/32 | 48 | 0.0940 | 2.38 | 0.0670 | 1.70 | 2.67 | 1.90 | ||
| 1/8 | 40 | 0.1250 | 3.18 | 0.0930 | 2.36 | 9/64 | 3.57 | # 38 | 2.60 |
| 5/32 | 32 | 0.1560 | 3.97 | 0.1160 | 2.95 | 11/64 | 4.37 | 1/8 | 3.20 |
| 3/16 | 24 | 0.1870 | 4.75 | 0.1340 | 3.40 | 13/64 | 5.16 | # 27 | 3.70 |
| 7/32 | 24 | 0.2190 | 5.60 | 0.1660 | 4.22 | 15/64 | 5.95 | # 19 | 4.30 |
| 1/4 | 20 | 0.2500 | 6.35 | 0.1860 | 4.72 | 17/64 | 6.75 | # 9 | 5.00 |
| 5/16 | 18 | 0.3120 | 7.92 | 0.2410 | 6.12 | 21/64 | 8.33 | 1/4 | 6.40 |
| 3/8 | 16 | 0.3750 | 9.53 | 0.2950 | 7.49 | 25/64 | 9.92 | 5/16 | 8.00 |
| 7/16 | 14 | 0.4370 | 11.10 | 0.3460 | 8.79 | 29/64 | 11.51 | U | 9.40 |
| 1/2 | 12 | 0.5000 | 12.70 | 0.3930 | 9.98 | 17/32 | 13.49 | 27/64 | 10.80 |
| 9/16 | 12 | 0.5630 | 14.29 | 0.4560 | 11.58 | 19/32 | 15.08 | 15/32 | 12.00 |
| 5/8 | 11 | 0.6250 | 15.88 | 0.5090 | 12.93 | 21/32 | 16.67 | 17/32 | 13.50 |
| 11/16 | 11 | 0.6880 | 17.48 | 0.5710 | 14.50 | 17.75 | 15.00 | ||
| 3/4 | 10 | 0.7500 | 19.05 | 0.6220 | 15.80 | 25/32 | 19.84 | 21/32 | 17.00 |
| 13/16 | 10 | 0.8130 | 20.65 | 0.6840 | 17.37 | 21.00 | 18.00 | ||
| 7/8 | 9 | 0.8750 | 22.23 | 0.7330 | 18.62 | 29/32 | 23.02 | 49/64 | 19.50 |
| 15/16 | 9 | 0.9380 | 23.83 | 0.7950 | 20.19 | 24.00 | 20.75 | ||
| 1 | 8 | 1.0000 | 25.40 | 0.8400 | 21.34 | 1 1/16 | 26.99 | 7/8 | 22.50 |
| 1 1/8 | 7 | 1.1250 | 28.58 | 0.9420 | 23.93 | 1 3/16 | 30.16 | 1 | 25.50 |
| 1 1/4 | 7 | 1.2500 | 31.75 | 1.0670 | 27.10 | 1 5/16 | 33.34 | 1 7/16 | 28.50 |
| 1 3/8 | 6 | 1.3750 | 34.93 | 1.1620 | 29.51 | 1 7/16 | 36.51 | 1 7/32 | 31.00 |
| 1 1/2 | 6 | 1.5000 | 38.10 | 1.2870 | 32.69 | 1 9/16 | 39.69 | 1 11/32 | 34.50 |
| 1 5/8 | 5 | 1.6250 | 41.28 | 1.3690 | 34.77 | 41.50 | 35.50 | ||
| 1 3/4 | 5 | 1.7500 | 44.45 | 1.4940 | 37.95 | 45.00 | 38.50 | ||
| 1 7/8 | 4.5 | 1.8750 | 47.63 | 1.5910 | 40.40 | 48.00 | 41.25 | ||
| 2 | 4.5 | 2.0000 | 50.80 | 1.7150 | 43.57 | 51.00 | 44.50 | ||
| 2 1/4 | 4 | 50.00 | |||||||
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