British Standard Brass (BSB)

Thread Form

p = Pitch = 1/TPI h = Basic Depth of Thread = 0.640327p r = Basic Radius = 0.137329p

Thread Tables

Nominal Diameter	T.P.I	Basic Depth of Thread	Basic Major Diameter	Basic Effective Diameter	Basic Minor Diameter	Tapping Drill	Clearing Drill
(inch)	(n/a)	(inch)	(inch)	(inch)	(inch)	(mm)	(mm)
1/8	26	0.0246	0.125	0.102	0.0757	2	3.3
1/4	26	0.0246	0.25	0.2254	0.2007	5.2	6.5
3/8	26	0.0246	0.375	0.3504	0.3257	8.5	9.7
1/2	26	0.0246	0.5	0.4754	0.4507	11.6	13
5/8	26	0.0246	0.625	0.6004	0.5657	14.75	16.25
3/4	26	0.0246	0.75	0.7254	0.7007	18	19.25
7/8	26	0.0246	0.875	0.8504	0.8257	21.25	22.5
1	26	0.0246	1	0.9754	0.9507	24.25	25.75
1,1/8	26	0.0246	1.125	1.1004	1.0757	27.5	29
1,1/4	26	0.0246	1.25	1.2254	1.2007	30.75	32
1,1/2	26	0.0246	1.5	1.4754	1.4507	37	38.5