British Standard Fine Threads (55 Deg Thread Angle) |
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| Thread Form Data | Tapping Drill | Clearance Drill | |||||||
| Diameter | O/Diameter | Core | Pitch | Depth | Radius | Effective Dia | T.P.I | Dec / Met / Frac | Dec / Met / Frac |
| 3/16" | 0.1875 | 0.1475 | 0.0312 | 0.0200 | 0.0046 | 0.1675 | 32 | 0.1562 - 5/32" | 0.1929 - 4.90mm |
| 7/32" | 0.2188 | 0.1730 | 0.0357 | 0.0229 | 0.0049 | 0.1958 | 28 | 0.1831 - 4.65mm | 0.2205 - 5.60mm |
| 1/4" | 0.2500 | 0.2008 | 0.0385 | 0.0246 | 0.0053 | 0.2254 | 26 | 0.2087 - 5.30mm | 0.2559 - 6.50mm |
| 5/16" | 0.3125 | 0.2543 | 0.0454 | 0.0291 | 0.0062 | 0.2834 | 22 | 0.2657 - 6.75mm | 0.3150 - 8.00mm |
| 3/8" | 0.3750 | 0.3110 | 0.0500 | 0.0320 | 0.0069 | 0.3430 | 20 | 0.3248 - 8.25mm | 0.3858 - 9.80mm |
| 7/16" | 0.4375 | 0.3663 | 0.0555 | 0.0356 | 0.0076 | 0.4019 | 18 | 0.3819 - 9.70mm | 0.4531 - 29/64" |
| 1/2" | 0.5000 | 0.4200 | 0.0625 | 0.0400 | 0.0086 | 0.4600 | 16 | 0.4375 - 7/16" | 0.5156 - 35/64" |
| 9/16" | 0.5625 | 0.4825 | 0.0625 | 0.0400 | 0.0086 | 0.5225 | 16 | 0.5000 - 1/2" | 0.5781 - 37/64" |
| 5/8" | 0.6250 | 0.5336 | 0.0714 | 0.0457 | 0.0098 | 0.5793 | 14 | 0.5512 - 14.00mm | 0.6406 - 41/64" |
| 3/4" | 0.7500 | 0.6432 | 0.0833 | 0.0534 | 0.0114 | 0.6966 | 12 | 0.6594 - 16.75mm | 0.7656 - 49/64" |
| 7/8" | 0.8750 | 0.7586 | 0.0909 | 0.0582 | 0.0125 | 0.8168 | 11 | 0.7812 - 25/32" | 0.8906 - 57/64" |
| 1" | 1.0000 | 0.8720 | 0.1000 | 0.0640 | 0.0137 | 0.9360 | 10 | 0.8957 - 22.75mm | 1.0156 - 1-1/64" |
| 1-1/8" | 1.1250 | 0.9828 | 0.1111 | 0.0711 | 0.0153 | 1.0539 | 9 | 1.0039 - 25.50mm | 1.1406 - 1-9/64" |
| 1-1/4" | 1.2500 | 1.1078 | 0.1111 | 0.0711 | 0.0153 | 1.1789 | 9 | 1.1319 - 28.75 | 1.2656 - 1-17/64" |
| 1-3/8" | 1.3750 | 1.2150 | 0.1250 | 0.0800 | 0.0172 | 1.2950 | 8 | 1.2402 - 31.50 | 1.3906 - 1-25/64" |
| 1-1/2" | 1.5000 | 1.3400 | 0.1250 | 0.0800 | 0.0172 | 1.4200 | 8 | 1.3594 - 1-23/64" | 1.5156 - 1-33/64" |
| 1-5/8" | 1.6250 | 1.4649 | 0.1250 | 0.0800 | 0.0172 | 1.5450 | 8 | 1-23/64" | -- |
| 1-3/4" | 1.7500 | 1.5670 | 0.1429 | 0.0915 | 0.0196 | 1.6585 | 7 | 1-19/32" | -- |
| 2" | 2.0000 | 1.8170 | 0.1429 | 0.0915 | 0.0196 | 1.9085 | 7 | 1-27/32" | -- |
| 2-1/4" | 2.250 | 2.0366 | 0.1666 | 0.1067 | 0.0229 | 2.1433 | 6 | 2-1/16" | -- |
| 2-1/2" | 2.500 | 2.2866 | 0.1666 | 0.1067 | 0.0229 | 2.3933 | 6 | 2-5/16" | -- |
| 2-3/4" | 2.750 | 2.5366 | 0.1666 | 0.1067 | 0.0229 | 2.6433 | 6 | 2-9/16" | -- |
| 3" | 3.0000 | 2.7439 | 0.2000 | 0.1280 | 0.0275 | 2.8719 | 5 | 2-3/4" | -- |