BSW and BSF Thread Dimensions Chart
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British Standard Whitworth (BSW)
BSW is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world’s first national screw thread standard, and is the basis for many other standards, such as BSF, BSP, BSCon, and BSCopper.
British Standard Fine (BSF)
British Standard Fine (BSF) is a screw thread form, as a fine-pitch alternative to British Standard Whitworth (BSW) thread. It was used for steel bolts and nuts on much British machinery, including cars, prior to adoption of Unified, and later Metric, standards. For highly stressed conditions, especially in motorcycles, a finer thread, British Standard Cycle (BSC), was used as well.
Tolerances should be considered when designing products. Values related to drilling and tapping can differ significantly depending on factors such as operating temperature and material.
Optimas are a full-service supply chain and manufacturing solutions provider. Before you design your next product or make updates to an existing product, consider partnering with Optimas to take advantage of our many capabilities.
For guidance only.
Thread Size | Threads per Inch | External Major Diameter | Internal Minor Diameter | Drill Size Clearance Hole | Drill Size Tapped Hole | ||||
---|---|---|---|---|---|---|---|---|---|
BSW 55 | 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 |
Thread Size | Threads per Inch | External Major Diameter | Internal Major Diameter | Drill Size Clearance Hole | Drill Size Tapped Hole | ||||
---|---|---|---|---|---|---|---|---|---|
BSF 55 | INCH | MM | INCH | MM | INCH | MM | INCH | MM | |
3/16 | 32 | 0.1875 | 4.76 | 0.1475 | 3.75 | 4.90 | # 22 | 4.00 | |
7/32 | 28 | 0.2188 | 5.56 | 0.1730 | 4.39 | 5.70 | # 15 | 4.60 | |
1/4 | 26 | 0.2500 | 6.35 | 0.2000 | 5.08 | 17/64 | 6.75 | # 3 | 5.50 |
9/32 | 26 | 0.2800 | 7.14 | 0.2300 | 5.89 | 6.10 | |||
5/16 | 22 | 0.3125 | 7.94 | 0.2540 | 6.45 | 21/64 | 8.33 | 17/64 | 6.75 |
3/8 | 20 | 0.3750 | 9.53 | 0.3110 | 7.90 | 25/64 | 9.92 | 21/64 | 8.33 |
7/16 | 18 | 0.4375 | 11.11 | 0.3660 | 9.30 | 29/64 | 11.51 | 3/8 | 9.53 |
1/2 | 16 | 0.5000 | 12.70 | 0.4200 | 10.67 | 17/32 | 13.49 | 7/16 | 11.11 |
9/16 | 16 | 0.5625 | 14.29 | 0.4820 | 12.24 | 19/32 | 15.08 | 1/2 | 12.70 |
5/8 | 14 | 0.6250 | 15.88 | 0.5330 | 13.54 | 21/32 | 16.67 | 9/16 | 14.29 |
11/16 | 14 | 0.6875 | 17.46 | 0.5960 | 15.14 | 17.75 | 15.50 | ||
3/4 | 12 | 0.7500 | 19.05 | 0.6430 | 16.33 | 25/32 | 19.84 | 43/64 | 17.07 |
13/16 | 12 | 0.8100 | 20.64 | 0.7100 | 17.92 | 18.25 | |||
7/8 | 11 | 0.8750 | 22.23 | 0.7590 | 19.28 | 29/32 | 23.02 | 25/32 | 19.84 |
1 | 10 | 1.0000 | 25.40 | 0.8750 | 22.15 | 1 1/16 | 26.99 | 29/32 | 23.02 |
1 1/8 | 9 | 1.1250 | 28.58 | 0.9830 | 24.97 | 1 3/16 | 30.16 | 1 1/64 | 25.80 |
1 1/4 | 9 | 1.2500 | 31.75 | 1.1080 | 28.14 | 1 5/16 | 33.34 | 1 9/64 | 28.97 |
1 3/8 | 8 | 1.3750 | 34.93 | 1.2150 | 30.86 | 1 7/16 | 36.51 | 1 1/4 | 31.75 |
1 1/2 | 8 | 1.5000 | 38.10 | 1.3400 | 34.04 | 1 9/16 | 39.69 | 1 3/8 | 34.93 |
1 5/8 | 8 | 1.6300 | 41.30 | 1.4600 | 37.21 | 37.50 | |||
1 3/4 | 7 | 1.7500 | 44.45 | 1.5670 | 39.80 | 45.00 | 41.00 | ||
2 | 7 | 2.0000 | 50.80 | 1.8170 | 46.15 | 52.00 | 47.00 | ||
2 1/4 | 6 | 2.2500 | 57.15 | 2.0366 | 51.73 | 58.00 | 53.00 | ||
2 1/2 | 6 | 2.5000 | 63.50 | 2.2866 | 58.08 | 64.00 | 58.00 |
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