BSB has a 26 TPI pitch through the whole range and is often confused with BS Cycle thread the difference being that brass thread has an angle of 55 degrees whereas Cycle is 60 degrees. Brass threads are usually confined to fittings and adjusters on cables. Brass thread taps and dies are sold and advertised as 26 tpi and are identified by the letters BSB.

 

Actions Size Outside Dia Inch Tpi Pitch Inch Core Dia Inch Radius Inch Thread Depth Thou Tapping Drill Size Inch Tapping Drill Size Mm Letter Or Number
1/8 0.125 26 0.038 0.076 0.005 25 0.079 2.0 47
1/4 0.250 26 0.038 0.201 0.005 25 0.204 5.2 6
3/8 0.375 26 0.038 0.326 0.005 25 0.332 8.5 Q
1/2 0.500 26 0.038 0.451 0.005 25 0.453 11.5 29/64
5/8 0.625 26 0.038 0.566 0.005 25 0.578 14.7 37/64
3/4 0.750 26 0.038 0.701 0.005 25 0.703 17.9 45/64
7/8 0.875 26 0.038 0.826 0.005 25 0.828 21.0 53/64
1 1.000 26 0.038 0.951 0.005 25 0.953 24.2 61/64
1 - 1/8 1.125 26 0.038 1.076 0.005 25 1.078 27.4 1 - 5/64
1 - 1/4 1.250 26 0.038 1.201 0.005 25 1.203 30.6 1 - 13/64
1 - 1/2 1.500 26 0.038 1.451 0.005 25 1.453 36.8 1 - 29/64