British Standard Fine (BSF)

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)
3/16	32	0.02	0.1875	0.1675	0.1475	4	4.9
7/32	28	0.0229	0.2188	0.1959	0.173	4.6	5.7
1/4	26	0.0246	0.25	0.2254	0.2008	5.3	6.5
5/16	22	0.0291	0.3125	0.2834	0.2543	6.8	8.1
3/8	20	0.032	0.375	0.343	0.311	8.3	9.7
7/16	18	0.0356	0.4375	0.4019	0.3663	9.7	11.3
1/2	16	0.04	0.5	0.46	0.42	11.1	13
9/16	16	0.04	0.5625	0.5225	0.4825	12.7	14.5
5/8	14	0.0457	0.625	0.5793	0.5336	14	16.25
11/16	14	0.0457	0.6875	0.6418	0.5961	15.5	17.75
3/4	12	0.0534	0.75	0.6966	0.6432	16.75	19.25
7/8	11	0.0582	0.875	0.8168	0.7586	19.75	22.5
1	10	0.064	1	0.936	0.872	22.75	25.75
1,1/8	9	0.0711	1.125	1.0539	0.9828	25.5	29
1,1/4	9	0.0711	1.25	1.1789	1.1078	28.5	32
1,3/8	8	0.08	1.375	1.295	1.215	31.5	35.5
1,1/2	8	0.08	1.5	1.42	1.34	34.5	38.5
1,3/4	7	0.0915	1.75	1.6585	1.567	41	45
2	7	0.0915	2	1.9085	1.817	47	52
2,1/4	6	0.1067	2.25	2.1433	2.0366	53	58
2,1/2	6	0.1067	2.5	2.3933	2.2866	58	64