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British Standard Fine (B.S.F.)
Thread Form
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- p = Pitch = 1/TPI
- h = Basic Depth of Thread = 0.640327p
- r = Basic Radius = 0.137329p
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Thread Tables
| Nominal Diameter |
T.P.I. |
Basic Depth of Thread |
Basic Major Diameter |
Basic Effective Diameter |
Basic Minor Diameter |
Tapping Drill |
Clearing Drill |
| (inch) |
(n/a) |
(inch) |
(inch) |
(inch) |
(inch) |
(mm) |
(mm) |
| 3/16 |
32 |
0.02 |
0.1875 |
0.1675 |
0.1475 |
4 |
4.9 |
| 7/32 |
28 |
0.0229 |
0.2188 |
0.1959 |
0.173 |
4.6 |
5.7 |
| 1/4 |
26 |
0.0246 |
0.25 |
0.2254 |
0.2008 |
5.3 |
6.5 |
| 5/16 |
22 |
0.0291 |
0.3125 |
0.2834 |
0.2543 |
6.8 |
8.1 |
| 3/8 |
20 |
0.032 |
0.375 |
0.343 |
0.311 |
8.3 |
9.7 |
| 7/16 |
18 |
0.0356 |
0.4375 |
0.4019 |
0.3663 |
9.7 |
11.3 |
| 1/2 |
16 |
0.04 |
0.5 |
0.46 |
0.42 |
11.1 |
13 |
| 9/16 |
16 |
0.04 |
0.5625 |
0.5225 |
0.4825 |
12.7 |
14.5 |
| 5/8 |
14 |
0.0457 |
0.625 |
0.5793 |
0.5336 |
14 |
16.25 |
| 11/16 |
14 |
0.0457 |
0.6875 |
0.6418 |
0.5961 |
15.5 |
17.75 |
| 3/4 |
12 |
0.0534 |
0.75 |
0.6966 |
0.6432 |
16.75 |
19.25 |
| 7/8 |
11 |
0.0582 |
0.875 |
0.8168 |
0.7586 |
19.75 |
22.5 |
| 1 |
10 |
0.064 |
1 |
0.936 |
0.872 |
22.75 |
25.75 |
| 1,1/8 |
9 |
0.0711 |
1.125 |
1.0539 |
0.9828 |
25.5 |
29 |
| 1,1/4 |
9 |
0.0711 |
1.25 |
1.1789 |
1.1078 |
28.5 |
32 |
| 1,3/8 |
8 |
0.08 |
1.375 |
1.295 |
1.215 |
31.5 |
35.5 |
| 1,1/2 |
8 |
0.08 |
1.5 |
1.42 |
1.34 |
34.5 |
38.5 |
| 1,3/4 |
7 |
0.0915 |
1.75 |
1.6585 |
1.567 |
41 |
45 |
| 2 |
7 |
0.0915 |
2 |
1.9085 |
1.817 |
47 |
52 |
| 2,1/4 |
6 |
0.1067 |
2.25 |
2.1433 |
2.0366 |
53 |
58 |
| 2,1/2 |
6 |
0.1067 |
2.5 |
2.3933 |
2.2866 |
58 |
64 |
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