bennypass.com - The BSPP fittings (British Standard Pipe)

The BSPP fittings (British Standard Pipe)

BSP = British Standard Pipe, or BSPP = British Standard Parallel Pipe, or BSPF = British Standard Parallel Fixed.

This thread needs a gasket or seal to be gas/liquid tight.
BSP (British Standard Pipe) Thread Data

Angle of thread = 55o degrees

bsp

1/16	28	0.0357	0.304	0.2583	Letter drill G (6.6 mm)
Nominal Size (inches)	T P I	Pitch (inches)	Major Diameter (inches)	Minor Diameter (inches)	Tapping Drill Size
1/8	28	0.0357	0.383	0.3372	11/32 inch (8.73 mm)
1/4	19	0.0526	0.518	0.4546	11.8 mm (0.4646 inch)
3/8	19	0.0526	0.656	0.5886	15.25 mm (0.6004 inch)
1/2	14	0.0714	0.825	0.7336	3/4 inch (19.05 mm)
5/8	14	0.0714	0.902	0.8106	21 mm (0.8268 inch)
3/4	14	0.0714	1.041	0.9496	24.5 mm (0.9646 inch)
7/8	14	0.0714	1.189	1.0976	28.25 mm (1.1122 inch)
1 inch	11	0.0909	1.309	1.1926	30.75 mm (1.2106 inch)