Specifications of International Thread Standards

British Standard Fine Thread Series (parallel, cylindrical).
BSW and BSF are the Thread selections for commercial screws and nuts. The Fine Thread, which is widespread in the Britisch machine tool industry, is superseded by the American UNF Thread.
The flank angle is 55°.

Nominal
Diameter
Major
Diameter
Inch
Major
Diameter
mm
Tapping
Drill Size
mm
TPIPitch
mm
BSF 3/16"0.18754.7633.950320.794
BSF 7/32"0.21885.5564.600280.907
BSF 1/4"0.25006.3505.300260.977
BSF 9/32"0.28127.1446.100260.977
BSF 5/16"0.31257.9386.750221.154
BSF 3/8"0.37509.5258.200201.270
BSF 7/16"0.437511.1139.580181.411
BSF 1/2"0.500012.70011.100161.587
BSF 9/16"0.562514.28812.600161.587
BSF 5/8"0.625015.87513.900141.814
BSF 11/16"0.687517.46315.500141.814
BSF 3/4"0.750019.05016.700122.117
BSF 7/8"0.875022.22519.600112.309
BSF 1"1.000025.40022.500102.540
BSF 1 1/8"1.125028.57525.40092.822
BSF 1 1/4"1.250031.75028.56092.822
BSF 1 3/8"1.375034.92531.35083.175
BSF 1 1/2"1.500038.10034.50083.175
BSF 1 5/8"1.625041.27537.71083.175
BSF 1 3/4"1.750044.45040.48073.628
BSF 2"2.000050.80046.83073.628
BSF 2 1/4"2.250057.15052.40064.233
BSF 2 1/2"2.500063.50058.74064.233
BSF 2 3/4"2.750069.85065.00064.233
BSF 3"3.000076.20070.50055.080
BSF 3 1/4"3.250082.55079.37055.080
BSF 3 1/2"3.500088.90082.5504.55.644
BSF 3 3/4"3.750095.25088.9004.55.644
BSF 4"4.0000101.60095.2504.55.644
BSF 4 1/4"4.2500107.950101.60046.350
Whitworth Fine Thread