British Association (BA)

Thread Form

p = Pitch h = Basic Depth of Thread = 0.6p r = Basic Radius = 0.1808346p

Thread Tables

BA No.	Pitch	Basic Thread Depth	Basic Major Diameter	Basic Effective Diameter	Basic Minor Diameter	Tapping Drill	Clearance Drill
(n/a)	(inch)	(inch)	(inch)	(inch)	(inch)	(mm)	(mm)
0	0.0394	0.0236	0.2362	0.2126	0.189	5.1	6.1
1	0.0354	0.0213	0.2087	0.1874	0.1661	4.5	5.4
2	0.0319	0.0191	0.185	0.1659	0.1468	4	4.8
3	0.0287	0.0172	0.1614	0.1441	0.1268	3.4	4.2
4	0.026	0.0156	0.1417	0.1262	0.1106	3	3.7
5	0.0232	0.0139	0.126	0.112	0.098	2.65	3.3
6	0.0209	0.0125	0.1102	0.0976	0.085	2.3	2.9
7	0.0189	0.0113	0.0984	0.087	0.0756	2.06	2.6
8	0.0169	0.0102	0.0866	0.0764	0.0661	1.8	2.25
9	0.0154	0.0092	0.0748	0.0656	0.0563	1.55	1.95
10	0.0138	0.0083	0.0669	0.0587	0.0504	1.4	1.75
11	0.0122	0.0073	0.0591	0.0518	0.0445	1.2	1.6
12	0.011	0.0066	0.0512	0.0445	0.0378	1.05	1.4
13	0.0098	0.0059	0.0472	0.0413	0.0354	0.98	1.3
14	0.0091	0.0054	0.0394	0.0339	0.0283	0.8	1.1
15	0.0083	0.005	0.0354	0.0306	0.0256	0.7	0.98
16	0.0075	0.0046	0.0311	0.0266	0.022	0.6	0.88