British Standard Cycle (BSC)

Thread Form

p = Pitch = 1/TPI h = Basic Depth of Thread = 0.5327p r = Basic Radius = 0.166p

Thread Tables

Nominal Size	T.P.I.	Basic Thread Depth	Basic Major Diameter	Basic Effective Diameter	Basic Minor Diameter	Tapping Drill	Clearing Drill
(inch)	(n/a)	(inch)	(inch)	(inch)	(inch)	(mm)	(mm)
1/8	40	0.0133	0.125	0.1117	0.0984	2.5	3.3
5/32	32	0.0166	0.1563	0.1397	0.1231	3.25	4.1
3/16	32	0.0166	0.1875	0.17085	0.1542	3.97	4.9
1/4	26	0.0205	0.25	0.22955	0.2091	5.56	6.5
9/32	26	0.0205	0.281	0.26065	0.2403	6.2	7.3
5/16	26	0.0205	0.3125	0.292	0.2715	7	8.1
3/8	26	0.0205	0.375	0.3545	0.334	8.65	9.7
7/16	26	0.0205	0.4375	0.417	0.3965	10.1	11.3
1/2	26	0.0205	0.5	0.4795	0.459	11.7	13
9/16	26	0.0205	0.5625	0.542	0.5215	13.1	14.5
5/8	26	0.0205	0.625	0.6045	0.584	15	16.25
11/16	26	0.0205	0.6875	0.667	0.6465	16.5	17.75
1	26	0.0205	1	0.9795	0.959	24.61	25.75