BRITISH STANDARD BRASS (BSB) THREAD DATA

British Standard Brass thread BSB

The BSB thread, based on the Whitworth thread, with an angle of 55°, these threads are generally used for thin walled tubing.

It has a standard 26 TPI across the range and is often confused with the British Cycle thread (BSCy), but BSB has an angle of 55°, whilst BSCy has angle of 60°

BSB TAPPING DRILL CHART

NOMINAL SIZE TPI PITCH TAPPING DRILL SIZE
inches no inches inches mm number /
letter Drill
1/8" 26 0.03846 0.0785 2.0 47
1/4" 26 0.03846 0.2040 5.2 6
3/8" 26 0.03846 0.3320 8.5 Q
7/16" 26 0.03846 0.39370 10.0 X
1/2" 26 0.03846 0.4531 11.5 29/64
5/8" 26 0.03846 0.5781 14.7 37/64
3/4" 26 0.03846 0.7031 17.86 45/64
7/8" 26 0.03846 0.8281 20.97 53/64
1" 26 0.03846 0.9531 24.2 61/64
1⅛" 26 0.03846 1.0781 27.4 1-5/64
1¼" 26 0.03846 1.2031 30.56 1-13/64
1½" 26 0.03846 1.4531 36.8 1-29/64