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British Association (B.A.)

Thread Form

BA Thread Form
  • p = Pitch
  • h = Basic Depth of Thread = 0.6p
  • r = Basic Radius = 0.1808346p

Thread Tables

BA No. Pitch Basic Thread Depth Basic Major Diameter Basic Effective Diameter Basic Minor Diameter Tapping Drill Clearance Drill
(n/a) (inch) (inch) (inch) (inch) (inch) (mm) (mm)
0 0.0394 0.0236 0.2362 0.2126 0.189 5.1 6.1
1 0.0354 0.0213 0.2087 0.1874 0.1661 4.5 5.4
2 0.0319 0.0191 0.185 0.1659 0.1468 4 4.8
3 0.0287 0.0172 0.1614 0.1441 0.1268 3.4 4.2
4 0.026 0.0156 0.1417 0.1262 0.1106 3 3.7
5 0.0232 0.0139 0.126 0.112 0.098 2.65 3.3
6 0.0209 0.0125 0.1102 0.0976 0.085 2.3 2.9
7 0.0189 0.0113 0.0984 0.087 0.0756 2.06 2.6
8 0.0169 0.0102 0.0866 0.0764 0.0661 1.8 2.25
9 0.0154 0.0092 0.0748 0.0656 0.0563 1.55 1.95
10 0.0138 0.0083 0.0669 0.0587 0.0504 1.4 1.75
11 0.0122 0.0073 0.0591 0.0518 0.0445 1.2 1.6
12 0.011 0.0066 0.0512 0.0445 0.0378 1.05 1.4
13 0.0098 0.0059 0.0472 0.0413 0.0354 0.98 1.3
14 0.0091 0.0054 0.0394 0.0339 0.0283 0.8 1.1
15 0.0083 0.005 0.0354 0.0306 0.0256 0.7 0.98
16 0.0075 0.0046 0.0311 0.0266 0.022 0.6 0.88
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Last modified: SolFlu  Sun, 28 Jun 2009 02:54:27 GMT